AU2013273826B2 - Electric fence system and components thereof - Google Patents

Abstract

A monitoring module that monitors pulses applied to an electric fence in an electric fence system including an energiser module for applying pulses to an electric fence. The monitoring module is arranged to monitor, within a dynamic time period, the pulses applied to the electric fence and to adjust the dynamic time period until an applied pulse is detected by the monitoring module within the time period. co co

Description

ι 2013273826 23 Dec 2013

ELECTRIC FENCE SYSTEM AND COMPONENTS THEREOF FIELD OF THE INVENTION

The present invention relates to an electric fence system and components thereof. More particularly, but not exclusively, the invention relates to a wireless electric fence system.

BACKGROUND OF THE INVENTION

Security electric fencing systems are used to protect persons or property. Any intruder touching a security electric fence wire will likely receive an electric shock from the fence, but in addition to this a security alarm may also be triggered to inform the user of the intrusion.

The electric fence is typically energised by a non-lethal pulse type energiser. An intruder contact is detected by an electric fence voltage or current monitoring circuit that picks up the change in the electric fence voltage or current caused by an intruder contacting the fence. A key success factor for a security electric fence system targeted at urban domestic installations is not only reliability, but affordability. Currently available systems tackle the affordability requirement by integrating all the system components into one product enclosure to reduce costs (energiser, monitor and system control logic). However this leads to further issues when a manufacturer attempts to gain compliance with international appliance safety standards and also meet the user’s expectations with regards to the aesthetics of the installation wiring. Urban domestic security electric fences are commonly installed on top of walls.

Safety standards related to electric fence energisers have become increasingly stringent in recent years. Particular attention is placed on high levels of isolation being required between the low voltage circuits and the fence circuits, typically this can involve impulse voltage testing at levels in excess of 25,000 volts. In 2 2013273826 23 Dec 2013 addition to electrical isolation, there are requirements that demand that safe operation is maintained when there is electrical component failure. Electronic devices that make use of firmware are now carefully scrutinised and the software code embedded therein thoroughly checked to ensure that product safety will be maintained under all conditions.

Any security electric fencing product that includes an energiser circuit in it needs to comply fully with every aspect of the international energiser standards. This requirement dictates that if a fence voltage monitoring circuitry is included, it must then comply with the 25,000V energiser requirement for isolation between the fence circuits and the low voltage input and control circuitry. Products are generally required to comply with international electromagnetic compatibility (EMC) standards and this can become quite difficult when many circuits and connections are included.

These “integrated energiser products” (used herein to refer to an energiser integrated with another unit, such as a monitor) typically use electronic devices that make use of embedded firmware to control the security system to ensure safe energiser operation. The software used will need to be more sophisticated than the software used in a basic energiser and the level of difficulty in ensuring the product safety is often much higher.

These integrated energiser products will typically include a number of electrical connection terminals that need to be handled by the security system installer or the user. These will include both high (electric fence) and low voltage (SELV & supply) type connections. These will likely include connections to the power supply, warning siren, strobe light, user controls, and feed and return connections to the electric fence. A significant practical problem is the sheer number of connections being made to circuits within the integrated unit and how the wires must be routed for both aesthetics and safety, remembering that high voltages are involved and must be well insulated and/or routed away from low voltage wiring. Another issue is that the connections to low voltage remote peripherals need to be isolated from any high voltages, such as the fence and the energiser 3 2013273826 23 Dec 2013 primary circuit voltages, typically 500-1000V DC. This requirement can lead to a number of expensive electrical isolation barriers being required.

Finding an ideal physical location for the integrated security electric fence product is often difficult. It must be located in a convenient place for daily use, but at the same time allow for easy wiring, with the minimum of disruption and inconvenience to the user during the installation period. Damage or even theft of the user’s property is often a concern at the time of installation. Special care is needed when routing the high voltage (10,000V impulse) fence wires, especially as these often need to be taken from opposite ends of the fence and then routed inside the walls of buildings. The safe isolation of these wires from other electrical equipment is critical and may well need certification by the local authorities.

Changes in the wiring, or adding extra user features to a system at a later date is often difficult and expensive to implement. Extra wires and system terminal connections are required and it is possible that re-certification of the equipment for safety and potentially EMC compliance will be needed.

An object of the present invention is to alleviate some problems associated with prior products, or to at least provide the public with a useful choice. In one arrangement, the use of wireless communications technology is proposed. This allows component parts of a security electric fencing system to be physically separated in an economical way into individual parts that can then be conveniently located. For example, the energiser component of the system may be of a simple design and will pass safety standards approvals more easily. Extra features and system parts may also be added without the need for additional wiring or re-certification of these parts of the installation.

DISCLOSURE OF THE INVENTION

According to one aspect of the invention there is provided a monitoring module for monitoring pulses applied to an electric fence in an electric fence system that includes an energiser module for applying pulses to an electric fence, wherein the 4 2013273826 23 Dec 2013 monitoring module is arranged to monitor, within a dynamic time period, the pulses applied to the electric fence and to adjust the dynamic time period until an applied pulse is detected by the monitoring module within the time period.

According to another aspect there is provided a method of monitoring pulses in an electric fence system, the method including the steps of: monitoring an electric fence within a dynamic time period to detect pulses applied to the electric fence and adjusting the dynamic time period until an applied pulse is detected by the monitoring module within the time period.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example with reference to the accompanying drawings in which:

Figure 1: shows a block diagram of a wireless electric fence system with an optional remote control.

Figure 2A: shows a block diagram of an energiser module.

Figure 2B: shows an image of an energiser module.

Figure 3A: shows a block diagram of a monitoring module.

Figure 3B: shows an image of a monitoring module.

Figure 4A: shows a first charge circuit for use in a monitoring module.

Figure 4B: shows a second charge circuit for use in a monitoring module.

Figure 5A: shows a block diagram of a system controller.

Figure 5B: shows an image of a system controller. 5 2013273826 23 Dec 2013

Figure 6A: shows a block diagram for a remote control.

Figure 6B: shows an image of a remote control.

Figure 7A: shows a signalling technique for a dynamic listening window.

Figure 7B: shows a signalling technique for interference control.

Figure 7C: shows a signalling technique for dynamic interference avoidance.

Figure 8: shows a graph of a low voltage operating system.

Figure 9: shows a block diagram of a multi sector electric fence system.

Figure 10: shows a block diagram of a gate switch device.

Figure 11: shows a graph of an energiser response.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In one configuration only three parts (energiser module, monitoring module and control module) are required for the system to work effectively. However, this configuration includes an optional remote control unit as described below. It will also be understood that additional components may be added to the system.

Figure 1 shows a wireless electric fence system according to this configuration.

An electric fence 101 has an energiser module 103 electrically coupled to it in order to provide energiser pulses. The energiser module 103 receives its power from a power source 105 via an input power line 107. A monitoring module 109 is connected to the electric fence 101 and is arranged to detect the electric pulses emitted by the energiser module 103. A control module 111 is in wireless communication with the monitoring module 109. 6 2013273826 23 Dec 2013

In this configuration, as will be explained in more detail below, the control module 111 includes a wireless transceiver that transmits and receives signals to/from the monitoring module 109 as well as transmitting signals to the energiser module 103. Further, the monitoring module 109 has a transceiver to transmit and receive signals to/from the control module 111. The energiser module 103 has a wireless receiver for receiving signals from the control module 111.

The system also includes an optional wireless remote control unit 113 that is in communication with the control module 111 via a wireless transceiver, as will be explained in more detail below.

Each of the components of the system will now be described.

The Electric Fence Energiser

This component of the system is used to generate the impulses of high voltage (10,000V) that are applied to the wires of the electric fence system. The pulse energy has been set to a maximum level of two joules, considered sufficient energy to meet the requirements of a typical urban house installation (1000 m2 site).

Figure 2A shows a block diagram for the energiser module and figure 2B shows its external appearance. The energiser module 103 includes a battery charger 201, a battery 203, power supplies 205, a pulse generator 207, a high voltage isolation barrier 209, timing and control circuits 211, a wireless receiver 213 and an antenna 215. A power supply input 217 provides power to the energiser module. A high voltage fence output 219 provides the high voltage pulses to the electric fence.

The energiser is powered from an external power supply, but an internal maintenance-free rechargeable battery contained within the energiser will maintain operation during periods of supply power interruption. 7 2013273826 23 Dec 2013

The Timing and Control circuits 211 have absolute control over the safe operation of the energiser. The receiver 213 allows reception of external control commands though a wireless link. The commands allow changes between different modes of operation only and cannot be used to impact on the safety of the product.

The energiser has external connections only to the electric fence 219 and power supply 217. The energiser operates using a universal ac supply 100V-240V 50Hz-60Hz. Other than these connections, the energiser may be fully encased and closed with no internal access given to the installer or user.

From an electrical safety perspective, the electric fence energiser is a “closed system” and can be tested and approved as a simple stand-alone part, without reference to the other component parts of the system. This is a key advantage over prior systems as it drastically simplifies the safety approval process.

As internal parts of the energiser do not need to be accessed, isolation from the input supply is not required. A more efficient electrical design has been achieved compared with traditional integrated security energiser designs that require a mains input double wound safety isolating transformer to be used to achieve Class 3 SELV (safety extra low voltage) safety.

The use of a standard mains double-wound step down safety isolating transformer in prior known integrated type energiser units introduces a secondary safety issue. When measured between the fence circuit and the mains circuit, the capacitance (typically 100pF) of the isolation barrier used in the mains transformer is effectively connected in series with that of the isolation barrier of the fence output isolation transformer (typically 50pF). During impulse conditions (normal operation) as well as during lightning impulse conditions an excessively high voltage can appear across the mains transformer isolation barrier and this can cause failure of the insulation leading to a potentially unsafe situation. Although a transformer secondary safety earth connection could be used to eliminate this problem as with any safety class 1 appliance (earthing metal case 2013273826 23 Dec 2013 8 parts on a kettle for example), the current international energiser safety standards do not allow safety class 1 construction.

In contrast to the above, this configuration does not require mains isolation other than to the fence, via the Output transformer, so the above identified problem does not occur. In addition, a spark gap discharge system can now be used to effectively divert lightning energy from the fence circuit into the mains supply circuit (well earthed system) and away from the electronic circuitry. This leads to a significant improvement in the reliability of the energiser over the prior known types that mostly use an external plug pack isolation transformer that has no spark gap internally.

International safety standards require all energiser products to have a high level of resistance to water ingress (IPX4). With prior known systems it is difficult to guarantee that this requirement is met when the product installer/user is required to make a multitude of wired connections to the product. Sealing these connections satisfactorily and/or replacing water sealing covers is often not done in a satisfactory manner and can lead to a safety hazard. The energiser described in this arrangement is completely sealed against water ingress as no connections need to be made to it other than the supply cable and the two fence connection terminals that are on the outside of the enclosure, thus eliminating this potential safety hazard.

The energiser unit as described in this arrangement can be physically located in any secure place where the high voltage wiring distance to the electric fence is short and where a power supply is available. This would typically be high up, out of sight and out of reach of children and pets. An installation might see the energiser mounted on an external wall, under the house eaves. In this location the high voltage electric fence cables do not need to be brought inside the building. This freedom of installation is in complete contrast to the constraints put on an installer when looking for a suitable installation to locate a traditional security type integrated energiser unit. 9 2013273826 23 Dec 2013

The Fence Monitor unit

The Fence Monitor unit is used to measure the amplitude of high voltage electric fence pulses generated by an electric fence energiser. The measurement information is internally processed and output as a wireless communication message. In this arrangement there are two external high voltage terminals provided on the monitor. These terminals are used to connect the monitor unit to the electric fence so that it can monitor the amplitude of the high voltage pulses appearing on the fence at that point.

The Monitor unit described is a completely self-contained unit, powered from an internal energy source (battery). The monitor is sealed and constructed to provide a long service life in a harsh outdoor environment.

Figure 3A shows a block diagram of a monitoring module according to this arrangement. The monitoring module includes a fence pulse input capture module 301, measurement and control circuits 303, a wireless transceiver 305, a battery 307, a battery monitor 309, a time base clock 311, and antenna 313 and two high voltage terminal connections 315.

The key advantage the Monitor unit of this arrangement has over traditional methods used is that it does not need to be located in close proximity to any other electronic part of the security electric fencing system and no connection cables are required between the monitor unit and other electronic parts of the system. With traditional electric fence security systems that use an integrated monitor, two bulky insulated high voltage cables are required between the fence monitoring point back and the integrated energiser unit that is located inside a building. In some cases the length of the cables is a problem and taking these high voltage cables back into the building is often difficult and presents several safety compliance issues and is expensive. To make the installation affordable lower quality insulated cables are often used and after only a short service life these cables start to break down and can cause safety and system reliability issues. ίο 2013273826 23 Dec 2013

Elaborate wire layout designs are often needed on traditional security electric fences to allow a convenient point for the monitoring high voltage return cables to leave the fence. In itself, this practice can lead to security risk as the monitoring feedback point and the energiser feed points are in close proximity and can be bridged by a jumper cable allowing the fence to be cut and breached at a distant point without the monitor detecting the breach.

When using the Monitor of this arrangement, it can be connected to virtually anywhere on the fence without regard to the location of the energiser feed wires. This freedom allows a comparatively simple fence wire layout to achieve enhanced levels of security on a lower installation budget.

Traditional integrated energiser fence monitoring circuits use transformers, optical couplers, or capacitors plus limited basic insulation to provide safety isolation between the electric fence circuit and the supply power circuit. As the physical electrical isolation distances are relatively small (8mm - 50mm), lightning strike or similar high voltage discharges can stress these isolation systems to the point that a breakdown failure can occur and a safety hazard is introduced. In contrast, with the fence monitor of this arrangement, there will be typically tens of metres of isolation between the fence circuit at the monitor and any supply circuit and absolutely no safety issues in this respect.

The fence monitor as shown in Figure 3B is completely self-contained. It has high levels of electrical isolation from outside to its internal circuitry and does not require any mandatory safety certification as it cannot create a safety hazard. Traditional Mains powered electric fence monitors on the other hand will require mandatory safety testing in many countries as they have the potential to create a serious safety hazard when faulty.

In this arrangement, a replaceable battery is used as an energy storage means and power source for the monitor. The electronic circuitry is designed to minimise energy consumption and a typical average current consumption on a prototype of 170uA has been observed for a 3V battery or 4mAh per day. A pair 11 2013273826 23 Dec 2013 of AA alkaline cells (2,500mAh) would be expected to last for well over a year before replacement is required.

As an alternative, a variety of alternative energy sources are suitable for use with the monitor electronics. Being an outdoor product the preferred choice would be to use a reusable energy resource such as the sun, wind or water. For example, a solar panel with rechargeable energy storage means could be used. Solar panel system performance requirements typically call for the ability to maintain operation for continuous periods of 10 sunless days in areas that see average winter monthly sun of less than 2 peak sun hours a day (for example, June in Dunedin, NZ).

Calculations show that a tiny solar panel capable of producing only 3mA charging current coupled with a small rechargeable 3V 45mAh lithium button cell (low leakage current) will meet this requirement.

Advantages of the solar powered system over a replaceable battery is that the product can be completely sealed at the time of manufacture and does not need the user to make battery changes and it can be made significantly smaller.

Rechargeable battery life expectancy can run to several years, but as with primary cells, this life is curtailed when the batteries are exposed to temperature extremes (>50eC) and the battery charging chemistry can be affected by low temperatures (<0eC). Lithium chemistry batteries do offer better temperature performance than most.

In contrast to batteries, Electric Double Layer Capacitors (Supercapacitors) operate well over a -25 eC to +75 eC temperature range and have an almost infinite charge/discharge life expectancy. An outstanding feature of Supercapacitors is their ability to accept high charge currents allowing them to be fully charged in just a few seconds. Once charged, a Supercapacitor can be left connected indefinitely to a fixed charging voltage without overcharging, whereas batteries often need careful charge management, with limited current and with the charge “end voltage” precisely set. The battery voltage is governed by the 2013273826 23 Dec 2013 12 battery chemistry and overcharging can damage the battery. For example the manufacturer of the aforementioned 3V 45mAh lithium button cell stipulates a maximum charge current rate of only 3mA. A Supercapacitor with a value of 8 farad and charged to 3.6V will release sufficient energy by the time its terminal falls to half voltage (1.8V) to allow the monitor to operate for up to 24 hours. A Supercapacitor can be used with an over powered solar panel without damage. This way the Supercapacitor energy storage means can be maintained in a fully charged state on even the darkest winter day, but without risk of over-current or overcharge damage on a bright sunny day. A small solar panel with a peak current output of 4V 10mA is capable of providing five times the daily energy requirements of the monitor in mid winter.

Less than 1 mJ of supply energy is required (30mA, 3V, 10ms) for the monitor to collect and transmit the fence voltage information. A capacitor energy storage means of only 0.00015F (150pF) is sufficient to supply this energy.

The energiser can supply up to 2 J of energy in a single fence pulse. So 2 mJ of energy bled from the fence pulse represents only 0.1% of the available energiser output and has negligible effect on the output. Flowever the extraction of this energy from the fence has previously been considered difficult as the pulse might typically be 5-10 kV DC in magnitude and have a duration of only 60 ps.

The circuit in figure 4A makes use of a resistor divider to extract energy from the electric fence. R1 and R2 divide the voltage received from the fence line and feed current via D1 to a charging capacitor C1. A zener diode is placed across C1 to supply a constant voltage to the electronic circuits of the monitor module. A resistor value of 3300 Ω is required to charge the 150pF capacitor. This circuit may put a noticeable load on the fence. Therefore, an alternative circuit can make use of a capacitor divider. Flowever, in a capacitor divider circuit pulse speed and shape becomes a critical issue in component selection. 13 2013273826 23 Dec 2013

As shown in Figure 4B, a secondary bulk capacitor storage bank can be added to the circuit shown in Figure 4A so that the monitor can store enough fence energy to operate over extended periods when there is little or no fence voltage.

The circuit includes a first stage of the resistor divider circuit of R1 and R2 and a diode D1 feeding a charge current to capacitor C1. Diode D2 feeds the RC circuit of R3 and C2 to charge C2. Diode D4 feeds the monitor electronics via zener diode ZD2 in order to limit the voltage applied. The charge on C1 is also fed to the monitor electronics via D3 and D5. This “standby energy” capacitor bank is arranged to charge slowly, taking deposits of energy from the fence while it is operational and then making the energy available to the monitor when the fence voltage is unable to sustain the monitor power requirements. Figure 4B shows a simple two bank circuit that uses the long period (1.5 seconds) between pulses to transfer the energy to the second capacitor bank. Further, the use of specialised pulse driven magnetics (flyback transformer) may also be utilised.

The System Controller

The System Controller shown in Figure 5A provides the user interface and controls the operation of the security electric fence system. The controller includes a battery charger 501, a battery 503, power supplies and protection 505, circuits for timing processing and control 507, a wireless transceiver 509, an antenna 511, an input module 513, an output module 515, user indicators 517, output devices such as a visual indicator or strobe 519 and a speaker or siren 521, switch input devices 523 or 525 and a power supply input line 527.

The system controller contains a powerful microcontroller and associated circuitry that will manage and control the system though wireless communications. The battery provides back up power to the system controller for times when mains supply power is cut off.

Designed to be located in a position most convenient to the user, the system controller communicates wirelessly with other devices in the system such as the Energiser and Monitor. In this arrangement, designed for low cost, the controller 14 2013273826 23 Dec 2013 includes a number of LED indicators, wireless transceiver, Siren &amp; Strobe outputs, Local audio warning device (buzzer), standby battery and battery charging circuit and Local input switch and auxiliary switch input.

All circuitry including the rechargeable battery may be safely contained within a single wall mounted enclosure as shown in Figure 5B. The siren alarm and strobe warning light may be hard wired. The battery charge is maintained through the use of an IEC SELV (Safety Extra Low Voltage) power supply that ensures the System Controller is IEC class 3 safety compliant (which means there are no high voltages present and you can touch any electrical part without risk of electrical shock). A single six core security cable could ensure a neat installation with only a single cable entry. Provision has been made for an auxiliary input contact that can be used to remotely arm through a wired contact. A description of the operation of the security electric fence system and the detection of a security breach now follows.

Starting from a disarmed (standby) state, the user places a magnetic key against a demarcated area on the front of the system controller activating a hall-effect input device and as a result the system becomes armed (active). In response the System Controller broadcasts a wireless message addressed to the Fence Energiser, which then responds by activating and producing high voltage pulses on the fence. The Fence Monitor captures and measures the peak fence voltage and broadcasts this information in a wireless message addressed to the System Controller, which will use it to check that the fence is in a healthy condition and the voltage is within acceptable limits. Status information is provided to the user through the System Controller Armed &amp; Pulse LED indicators.

The System Controller monitors the voltage on the electric fence using the wireless information received from the Monitor. If the voltage deviates suddenly from the mean level the System Controller responds to this as an electric fence breach and raises the alarm by sounding the Siren, activating the Strobe light as well as indicating the event directly to the user via the Alarm LED and buzzer. 15 2013273826 23 Dec 2013

The user can disarm the system using the magnetic key in the same way it was used to arm the system, then the System Controller broadcasts a wireless message addressed to the Fence Energiser, which then responds by deactivating and ceasing to feed high voltage pulses onto the fence.

It will be understood that the complexity of control required to implement a commercially viable security electric fence system is high and a full system operation manual is usually contained inside a substantial installation manual consisting of many pages. The software engineering needed to cover the many system states and user options requires a significant investment.

Traditional integrated energiser units need the system control electronics and software built into the product. All software and hardware interfaces, both external and internal must be fully defined at the initial design time as product changes cannot be made after mandatory safety approval without re-submission.

The System Controller of this arrangement does not require mandatory safety certification and installation and wiring can be performed by a person without electrical registration. The control software of the complete system can be changed freely at any time without affecting safety approvals. Upgrading the System controller hardware and software, adding features and enhancements can be done at any time to meet the latest customer expectations, again without affecting safety approvals or compliance with safety standards.

Remote Control A portable remote control device that uses wireless technology is also provided as an option. The Remote Control block schematic is shown in Figure 6A.

The remote control unit includes an input capture module 601, control circuitry 603, a battery 605, a battery monitor 607, a wireless transceiver 609, user indicators 611, an antenna 613, a command indicator 615, an acknowledge indicator 617, input buttons 619A-D for arming disarming, low voltage control and panic alarm. 16 2013273826 23 Dec 2013

The Remote Control 621 is small and can be conveniently carried in a pocket or on a key ring, see Figure 6B. It is designed to allow the user to control the system operation from any point near to the Security Electric Fence installation. The Remote control communicates with the System controller and is used to arm and disarm the system using the appropriate Arm and Disarm buttons (623, 625) on the Remote Control. The remote control also includes low voltage operation button 629 and a panic button 631.

Two coloured indicators 627 are included. A red indicator (command) and a green indicator (acknowledge). In this arrangement, the indicators 627 are provided as a single unit. It will be understood that separate indicators may also be provided.

The red indicator illuminates for a short period after a button has been pressed signaling to the user that a command was sent from the remote control. On receipt the System Controller takes action and sends a wireless message back to the Remote Control acknowledging this. The Remote Control indicates the success of a command by illuminating the Green indicator satisfying the user that the command has been performed.

It will be understood that the status indication may be provided in the form of a visual, tactile or audible indication.

The System Controller routinely transmits a short wireless broadcast acknowledgement after each wireless message received from the Fence Monitor. When the Remote Control is used to arm the system, the Remote Control listens to these acknowledgements for a short period (ten seconds) and flashes an indicator in sympathy. While the fence voltage is not within acceptable limits the indicator flashes red otherwise it will be green. By watching the indicators and waiting for the green flashes, the user is given an opportunity check that the system is operating correctly. Alternatively the user can disarm the system should the indication not turn green after a few seconds and thus prevent the alarm from 17 2013273826 23 Dec 2013 triggering. This action allows the user to check the fence integrity using the remote without needing to look at the indicators on the System Controller.

Wireless performance

In this arrangement, ultra low power UHF wireless transceivers and receivers are used that operate in the licence free ISM (Industrial, Scientific and Medical) bands inside the 800 - 928 MHz range with GFSK (Gaussian Frequency Shift Key) modulation. However, it will be understood that a wireless system preferably requires wireless communication that has low energy consumption and dependable wireless connectivity.

The output power allowed in the ISM bands is restricted to a few milliwatts giving a range of the operation that is limited to a few hundred metres. This is ideal for the intended application area of coverage for this system.

The transceivers employed are highly configurable and have sophisticated features, including multi-channel, frequency hopping, handshaking, packet handling, forward error correction, data buffering, burst transmissions, clear channel assessment, link quality indication (receive power) and wake-on-radio (interrupt control system), adjustable power output. The system is able to operate at high digital data transfer rates (up to 500 kbps) and still maintain a robust communications, with a minimal number of lost transmissions. The transceivers' messages include a specific destination address so wireless components can be addressed individually or as a group (group broadcast).

The transceiver used in each wireless system component is capable of two way communications (half duplex) however for some system components it is preferred to restrict this to “mainly transmit” or “mainly receive” mode only.

In the case of the Monitor, preserving stored energy (battery power) is a key requirement and every effort is made to achieve this goal. At all times when the Monitor is not processing a measurement the Monitor is put into a “Sleep” mode and this only consumes a few microamperes of current. Normal transceiver 18 2013273826 23 Dec 2013 operation involves some “hand shaking” between wireless parts. For example, after a transmission, the Monitor transceiver switches to receive mode to listen for a receive acknowledgement from the System Controller

The ultra low power transceivers consume a similar amount of energy in “receive mode” as they do in “transmit mode”, so by configuring the transceiver to operate in “transmit mode” only, the receive energy can be saved. In some cases, this simplex (one way) communication can be used, dispensing with handshaking and in many cases where the transmission channel is clear, no difference in system performance will be observed. In cases where the communications channel is noisy, “open loop” simplex communication can lead to unsatisfactory system performance as the Monitor will be unaware its message transmission was successful. It will also be understood that the transceiver may be substituted with a transmitter to reduce the cost of the wireless components.

In one method the transmit power control and link quality features of the transceiver are used to save Monitor storage energy, yet still maintain system reliability. The transmit power of the Monitor transceiver section can be software controlled over a -30dBmW to +10dBmW range, this affects the current consumption of the transceiver during transmission over a range of 12mA to 33mA respectively. The receive current essentially remains constant at around 15mA while switched to receive. The message transmit and receive (listen) times are also similar at around 10ms each. When the System Controller receives a message from the Fence Monitor, the wireless receive signal strength is automatically measured. The System Controller can process this information and determine the current quality of the RF link. This information is then fed back to the Monitor as part of the acknowledge signal. The Monitor will use this information to adjust its power output to an optimum level in an attempt to minimise the transmission current while still maintaining an acceptable receive signal level at the Controller. This can reduce the power consumption by 14% when compared with a “transmit only” system, however only when the transmission link is exceptionally clear. One key aspect of this method is for the monitor to listen to the return acknowledgements only occasionally. A sample 19 2013273826 23 Dec 2013 ratio of 1:10 can yield a potential power saving of 60% when compared with a “transmit only” system.

The link quality of the transmission path changes depending on the time of day and atmospheric conditions. The monitor is expected to continually adjust the transmission power levels to maintain an appropriate receive signal level. On cool clear nights the transmission path quality would be at its best and it may be essential to reduce the transmission power levels to reduce interference on other similar systems installed on neighbouring properties.

In cases where there is a sudden drop off in transmission path quality (due to a temporary obstruction etc.), the receive level may reduce such that the monitor does not receive an acknowledgement message from the System Controller. This can be due to a missed message on either side. In this case the Monitor may step up to maximum transmission power in an attempt to re-establish communications. Advanced system control techniques can be used to provide the smoothest power level control and yet maximise system data integrity.

The Monitor block schematic shown in Figure 3A indicates that a Time Base Clock 311 is included. This clock allows the monitor to initiate the time dependent actions that allow advanced features to be implemented.

It will be understood that this arrangement may be modified such that the monitor does not have a Time Base Clock and instead uses a fence pulse to bring the Monitor out of “sleep” mode. However, once out of sleep mode the monitor does not know when the last pulse was received or the age of the historical data it may have maintained during sleep. Therefore, the Time Base Clock of this arrangement allows the monitor to perform time based measurements, such as measuring the time periods between pulses, time trends and time average measurements.

The internal Time Base clock can be used to “wake” the Monitor out of “sleep” mode and continue to maintain periodic communications with the System Controller when there is no fence voltage. This is important if the system 2013273826 23 Dec 2013 20 controller is to be able to distinguish between a communications problem and a security fence breach (someone cut the wire). A communication loss can then be handled differently by the System Controller than it would a fence breach. A fence breach may be handled immediately, sounding a siren alarm etc., whereas a communications loss would usually be tolerated for a while before action is taken and even then the warning to the user would usually be less alarming (such as a flashing LED, buzzer etc.).

In urban areas where security electric fencing systems are used it is typical for a number of independent systems to operate in close proximity and interference between systems is likely. One particular noise source is pulse voltage pickup between fences. This is mainly due to electromagnetic induction between fence wires, although sometimes this can also be complicated by earth return path issues. In any event the result is that pulse voltages can be picked up by the Monitor that do not originate from the system energiser.

This interference can be problematic to the monitor. For example, a stray voltage pulse can cause the Monitor to leave low current “sleep” mode (to measure, process and wirelessly communicate the measurement) increasing the average current consumption and reducing battery life.

Also, in extreme cases of interference, the System Controller may find it difficult to determine which pulses detected are pulses originating from the Energiser that is part of the system.

Finally, in a case where the fence wire is cut somewhere between the Monitor and the Energiser, the low impedance (10 ohms) permanent load of the energiser output transformer is suddenly removed from the monitored section of fence, leaving a floating network of well insulated fence conductors. In this condition, pulse voltages of several thousand volts can be induced in the wires from other fence systems in close proximity. These voltages could even exceed the normal voltage level on the fence originating from the System Energiser. 21 2013273826 23 Dec 2013

One method of allowing for fence interference of this type is to use a combination of synchronisation, characterisation and correlation techniques.

Using the internal Time Base Clock, the Monitor is able to anticipate the expected arrival time of the incoming energiser fence pulses. It can then create a “listening” window 701, synchronised to the period 703 of the Energiser, see Figure 7A. It can ignore other interference “wakeup” pulse interrupts that fall outside the window of interest. Even with a 10% window this technique can mask out 90% of fence borne pulse noise and thus preserve Monitor storage energy. In the absence of energiser pulses, the window will gradually open up and will be left at full width until energiser pulses are received after which the window will be closed up for optimum performance.

Also, the window may be shifted in order to synchronise with the detected pulse and the window may then be reduced in size once the pulse has been detected. For example, the window may be shifted such that the centre of the window is in line and synchronized with the centre of the detected pulse.

In noisy environments, the Monitor may find it difficult to establish pulse synchronisation with the energiser and additional strategies are needed to ensure satisfactory operation. There are a number of schemes that can be implemented involving the Energiser, Monitor and System controller, one of which is described below.

After running the energiser for a while, the system controller can stop the energiser and if there are still voltage pulses being reported by the monitor then there is interference present. The Controller will then include extra information in its usual acknowledgement message to the Monitor, advising it of the situation.

The Monitor is able to analyse the interference noise amplitude and period. In most cases there will be only one dominant interfering energiser noise source, although sometimes there may be more. Where the amplitudes of the interfering voltages are low in comparison with the system Energiser pulse, a simple “squelch” function can suffice to prevent them from activating the monitor. The 22 2013273826 23 Dec 2013 influence of a dominant interference pulse may need special removal by the use of a software function that synchronises with the interfering pulse period 707 and then using the Time Base Clock is able to mask out the interfering pulse 709 and prevent the Monitor from being disturbed by it as shown in Figure 7B.

An embedded software function will track both the Energiser pulses and the interfering pulses. The pulse rates and amplitudes will be different and from time to time will overlap. During the overlap periods the Noise Window will overlap the Pulse Window. At this time the integrity of Energiser pulse voltage measurements will be low and this is flagged to the controller, so that the appropriate action can be taken. In one example, the alarm response is disabled until the windows separate.

The Monitor will wirelessly pass information to the System Controller about the pulse positions and periods of the System Energiser pulse and the interfering pulses. The System Controller will analyse the information and then can send a message to the energiser commanding it to change the pulse delivery timing and pulse period to break the window overlap and then minimise the recurrence. Alternatively the analysis could be performed by the Monitor itself, prior to passing information to the System Controller.

In some situations, the presence of a high voltage fence interference pulse may indicate that a direct fence connection to another fence system has been made. This situation can be dangerous, as any contact with the fence could result in a double shock possibly resulting in ventricular fibrillation. International safety standards dictate that a pulse repetition period must not be less than 1 second under normal conditions, but in abnormal conditions this can be allowed to drop down to a 0.75 s period. In addition to this the standards require that the total energy on a fence when the overall pulse repetition period is less than 0.75 seconds is limited to 2.5 joules per second into 500 ohms. It will be understood that in a system with a monitor that only measures and reports fence voltage and not pulse width and is thus unable to report the total pulse energy rate potential into a load of 500 ohms, the controller can be configured to treat this abnormal condition as a critical safety issue, raise a system alarm and stop the energiser. 23 2013273826 23 Dec 2013

Referring to Figure 7C, in the case where the interference pulse repetition period is 1.5 s or greater, the System controller can also take the option to wirelessly control the System Energiser to deliver pulses that fall in the exact centre period 711 between the interfering pulses and thus be able to maintain security and also safety. This is effectively active pulse synchronisation through “dynamic avoidance” rather than through deliberate synchronising.

For example, when two independent fence systems are inadvertently coupled together, each system will independently implement a “dynamic avoidance” strategy. The pulses will initially avoid each other, finding the centre space, but after establishing this configuration each energiser will start to “push space” by making small time advances right of “centre space”, indicating the desire for an increased pulse repetition period. Both energisers will respond and the pulse repetition periods will increase until a pulse repetition period of 2 seconds for each energiser is achieved, giving an overall spacing between all pulses of 1 second.

Both systems can continue to operate safely and can still provide electric fence security albeit with a subsequent larger pulse interval. Meanwhile the System Controllers will respond appropriately and warn the users that there is a fence connection fault. Once the system is disarmed, re-arming can be prevented until the fence fault is cleared.

One particular issue related to all electric fences is the situation where a Mains power conductor makes contact with the fence structure. In most cases this is an accident, but in some cases this is even done deliberately in an attempt to damage the electric fence energising equipment. This situation is extremely dangerous and a critical safety issue; a person touching the fence can receive a fatal shock. The Monitor described in the invention is able to detect and withstand standing ac mains line voltages. The high pulse repetition rate (50Hz -60Hz) is used to signal that a dangerous standing voltage on the fence and the message to the System controller from the Monitor will contain a warning alert that is used to raise the alarm warning the user of the dangerous condition. 24 2013273826 23 Dec 2013

Low voltage monitoring mode

The user often requires the integrity of the security electric fence wiring installation to be monitored, but not for the fence to deliver a painful shock. This might be when young children play in the vicinity of the electric fence and might inadvertently touch or fall on the fence. The invention includes Low voltage monitoring mode to provide this feature. The Energiser is commanded to deliver only a low voltage pulse to the fence in the order of 500 to 1000 volts. The maximum energy contained in the pulse is only in the order of 10mJ and is completely harmless, felt only as a healthy tingle. The monitor can still detect changes in the voltage level of this pulse and thus detect possible fence breaches and tampering.

Due to the incumbent electrical isolation issues, traditional security energiser systems have pulse measurement circuits that can’t reliably measure pulses down to such a low voltage on the electric fence. Typically optical isolation devices or isolation transformers are used and these have inherent accuracy or long term drift problems. Some of these traditional monitoring methods provide only the most basic detection capabilities and can detect only the total absence of the pulse, which is less useful. The tendency is for traditional security energiser systems to need higher voltage levels to allow the voltage monitoring system a better chance to work. These higher operating voltages drive higher energy (250 mJ) that will give quite a painful shock and cause distress.

The Monitor described herein has no isolation issues as the output is a wireless message. The non-isolated input measurement circuitry is thus capable of maintaining a high level of accuracy over a wide range of input voltages and environmental conditions and can provide a pulse voltage resolution of a few tens of volts. With a measurement system of this type it is possible to detect comparably small changes in fence voltage even when the fence voltage is at the extreme low end of the measurement scale. The voltage response curves for the system described are shown in figure 8. It can be seen that for most fence loads the voltage variation for a 1000 ohm fence contact is greater than 90 volts or 20% 25 2013273826 23 Dec 2013 and even with a fully loaded fence, for example a standing load 200 Ω, the voltage variation is greater than 30 volts. The above described system can thus detect fence tampering and fence contacts in both full voltage and low voltage monitoring modes.

It will be understood that when the System Controller is not transmitting a message it is configured to be in continuous receive mode; unlike the Monitor it is not supply energy constrained.

Advanced implementations of the invention

The above described arrangement has been limited to describe a base implementation of certain aspects of the invention

The arrangement incorporates separate functional blocks needed to implement a security electric fence system and then wirelessly connects them together to make the single system functional. As previously discussed, each system part has separate safety compliance requirements, but one key point is that the Energiser unit is the only part that requires mandatory international safety standards approval or proof of safety standards compliance. The safety of the energiser is inherent in its design and no wireless command or otherwise can compromise this safety. One can see that various design changes may be made to the other system parts which will not affect the energiser.

FURTHER ARRANGEMENTS

Various changes and modification may be made to the arrangements described herein, without departing from the scope of the present invention. It will be understood that, as an alternative, the remote control unit may control the energiser module or monitoring module directly without the control module, and that the Energiser module or Monitor Module can receive and then pass on messages received from the remote control to the System Controller module or energiser module, respectively. 2013273826 23 Dec 2013 26

Multi-Sector Security Electric Fencing System Multiple Monitor Systems

In some instances a single site application requires different sections of security electric fence to be monitored independently from each other. Rather than fitting a multiplicity of independent security electric fence systems on the site, a better result can be achieved by placing a wireless Monitor unit on each of the sections of fence and configuring a system so that a single System Controller can communicate with them all. Figure 9 shows such a system. Multiple monitors (909A, 909B, 909C) are connected to different sections of the fence (901 A, 901B, 901C). The system includes the same components as described before: an energiser 903, a power supply 905, an input power line 907, a controller 911 and a remote control 913.

The multi-sector type System Controller can display the status of each Monitor using an LED/LCD display in a similar way to the way a regular burglar alarm system manages different zones.

The wireless communications used in the multi-monitor system is more complex than the single Monitor system. Although the System controller will have no difficulty processing the multi-monitor data, the Monitors compete for airtime with the System controller and thus special consideration is needed. Assuming all sections of fence are powered from a single Energiser, each Monitor potentially seeks airtime with the System Controller at around the same time, which is a problem.

To combat this problem the System Controller issues every Monitor with a unique “stand-down” time that must be maintained before it transmits a message to the System controller after measuring an Energiser pulse. This simple technique minimises transmission overlap issues. The Monitors will also automatically briefly check that the communications channel is clear just prior to transmitting. 27 2013273826 23 Dec 2013

Additional System Components

In the above described preferred arrangement of the invention the basic system includes the components, Energiser, Monitor, System Controller and Remote Control. One key advantage of this system over other methods is the ease with which the system can be expanded and upgraded. Traditional methods often require hardware options and features to be included or at least allowed for in the base product. This overhead typically increases the base product cost penalising users who do not need the extra features.

Wireless components

System options and additional features can be added to the basic system by simply adding wireless component modules as required. In some cases it might also be necessary to upgrade the embedded software in other modules such as the System Controller or Monitor. A significant number of optional system components have already been conceived including those listed below, but the important aspect of the engineering is the creation of an appropriate software operating system that caters for the range of module configurations that the application requires. This again is a major feature of the invention as it allows for continuous improvement as improved software becomes available.

Remote Keypad

This device is a fully functional wireless security keypad module that can be mounted in any place convenient to the user that is within wireless communication range. The key feature is that it requires absolutely no wiring. This device is battery powered (2 x AA batteries) using a low current LCD display and/or power managed LED indicators to maximise battery life. An optional power supply/battery charger can also be used when Mains power is available.

The remote keypad adds to the system with a device that allows the possibility for the system to be configured on site for a number of user options that are different to the default settings that are loaded at the factory. The remote keypad allows 2013273826 23 Dec 2013 28 for a PIN (Personal Identification Number) system to be implemented with different users enjoying differing access rights.

The remote keypad can be configured as a remote utility device, such as a wireless programming module.

Wireless Programming and Updating

The wireless electric fence system can contain several wireless module parts, some of which are totally sealed against environmental damage by the use of difficult to remove waterproofing materials and it is not possible to access the electronic modules.

During manufacture, special “Wireless Bootloader” firmware is programmed into the module using wired programming tools. This software code segment is loaded into a special memory location in the microcontroller device that is used as the controller of the wireless module. This code is accessed and run in special circumstances, for example when the microcontroller “boots up” (starts) when power is first applied or after receiving a specific sequence or combination of wireless or input events. When executed, this Bootloader code can establish a secure high speed wireless communications link with a wireless programming module that is used to load “application” software into the main firmware code section of the microcontroller (Flash) memory. After checking and verifying the integrity of the newly loaded code it can then direct subsequent program instructions to be executed out of the main code section of the microcontroller device memory.

This wireless programming feature of the invention provides a high level of system flexibility. Each wireless module that has a transceiver has the capability to be updated, upgraded or reconfigured at any time after manufacture to perhaps meet new user requirements or simply to fix firmware bugs. 29 2013273826 23 Dec 2013

One advanced programming feature that is useful stems from the fact that in hardware the Bootloader code section of the microcontroller resides in a different section of code space to the main code. 1. Firstly the wireless Bootloader firmware is used to wirelessly load special wireless programming firmware into the main code area. 2. This main code application firmware is then executed and it again establishes a secure high speed wireless communications link with a wireless programming module that is used to load new Bootloader software into the Bootloader code section of the microcontroller (Flash) memory. 3. Finally this Bootloader code is executed which again establishes a secure high speed wireless communications link with a wireless programming module that loads “application” software back into the main firmware code section of the microcontroller (Flash) memory and the operation is complete.

The above sequence of events will allow even the original wireless Bootloader code to be upgraded wirelessly when desired.

Remote Electric Fence Gate Switch

This device is particularly useful in a security electric fencing system.

There are two prior known options currently available. These are the high voltage mechanical gate switch and the low voltage gate switch. Both of these options bring their own problems as follows.

In the case of the high voltage gate switch, this large mechanical switch device is connected in series with the electric fence conductors. When the gate is opened the switch contacts open and break the fence circuit causing the voltage to drop to zero and triggering the alarm. Although commonly used due to their simplicity, these switches are notoriously unreliable and tend to spark and burn whenever 30 2013273826 23 Dec 2013 the gate or gate switch is poorly fitted or adjusted, or when the gate is simply not closed effectively. High voltage gate switches also tend to be large, expensive and difficult to fit.

The low voltage gate switches are wired separately from the electric fence circuit using a low voltage feed cable. Low voltage gates switches are reliable and easier to fit on the gate than the high voltage type. However, one problem with low voltage gate switches is the need to run separate low voltage cables from the gate back to the security system controller. Safety standards dictate that these cables must be run in a separate cable conduit from any high voltage wires including normal mains wiring, for example, 230V. This can result in a high cost of materials. Also installation costs are high due to the difficulty in laying cables underground and ensuring waterproof connections.

The circuitry and cables connected to low voltage electric fence gate switches are vulnerable to a high voltage flashover from the fence pulse during normal operation and even more damage can result from the fence being struck by lightning. Special surge rated devices are added in an attempt to combat this problem.

According to this arrangement of the invention a wireless gate switch is included in the system. Figure 10 shows a gate switch that includes a gate switch input module 1001, control circuitry 1003, a wireless transceiver 1005, a battery 1007, a battery monitor 1009, a time base clock 1011, an antenna 1013, a Hall Effect switch 1015 and gate inputs (1017, 1019).

In its preferred form the wireless gate switch is similar to the monitor in its construction in that it is fully sealed and may also be waterproofed. It can utilise similar energy source options including, batteries, renewable energy charging, fence energy charging and the use of rechargeable batteries and/or Supercapacitors. In this arrangement, the switch function is a magnetic Hall Effect switch 1015 and rare earth magnet combination, which allows total weather sealing. It will be understood that other switch functions may be used, such as mechanical switches. The rare earth magnet is small in size but can 31 2013273826 23 Dec 2013 produce a strong concentrated magnetic field to activate the Hall Effect switch. This feature, together with a secure mechanical design makes the switch resistant to tampering by the use of magnetic tampering devices.

The wireless gate switch requires no wiring and installation is significantly easier and quicker than the methods described above.

The wireless gate switch communicates with the controller using the wireless transceiver 1005 and antenna 1013. The preferred scheme uses transceiver communication, but it will be understood that a “transmit-only” alternative can be used.

As with the fence voltage monitor, power consumption is a critical factor and wireless transmissions are to be minimised. In the preferred form, communications are initiated by the gate switch, which has two modes. The two modes are routine status reporting mode and gate change mode.

Routine status reporting consists of a single transmission to the controller, for example, on average every minute, but this period may be randomly varied and be dependant on the current device status, for example the charge status of the battery 1007. This message confirms the current status of the gate plus any diagnostics information, such as, for example, battery condition etc. The gate switch expects and acknowledgement message back from the System Controller. Without acknowledgement the gate switch may send a repeat message to cover the situation where the System controller was too busy to acknowledge. Without any received acknowledgement the gate switch may continue to transmit blind at regular intervals.

An acknowledgement message from a routine status transmission may contain information that may also be used to initiate other activities such as wireless programming of the gate switch or time logged data.

The wireless gate switch electronic circuitry is electrically isolated and has no external terminals or wire connections and so will not suffer from the effects of high voltage flashover from the fence pulse or from the fence being struck by lightning. 32 2013273826 23 Dec 2013 A plurality of gate switches may be included in one wireless electric fence control system. The wireless gate switch is not limited to electric fencing gates and can be used in a variety of similar applications.

Additional wireless security systems components A number of additional wireless modules may be added to the wireless electric fence system that may add system utility without the need for additional hard wiring. These include: a wireless siren module, a wireless strobe module, a wireless repeater module, where wireless devices are located outside the normal wireless range, a wireless bridge module, where communication with other wireless devices outside of the system are to be included, for example, remote monitoring or neighbourhood watch, a wireless cellular link module for cellular phone based automation and monitoring, a wireless internet bridge for web based system monitoring, a wireless fence earth quality monitor, a wireless automatic gate interface module, and a wireless link to an existing home alarm system.

Advanced Electric Fence Monitor Unit

The Monitor described thus far has only one input primarily used for measuring peak fence pulse voltage. In addition the monitor may maintain a limited amount of self-diagnostic functionality, such as monitoring battery charge state, device errors, etc. This diagnostic data is included in regular wireless transmissions so that the controller can advise the user if maintenance is required such as changing the battery.

An advanced version of the Monitor (AWM) is able to monitor a combination of inputs and create outputs based on these measurements containing both raw 33 2013273826 23 Dec 2013 and derived data, in the form of a wireless communication with other system components. The current prototype designs use a wireless transceiver packet data size of 64 bytes, which allows plenty of room for measurement data. A single transmission can contain a number of packets.

The AWM can take multiple measurement samples of fence voltage &amp; fence current over the duration of the measurement window as well as pulse width measurement. Other measurements may be included, such as temperature, battery data (Supercapacitor data) plus the solar system information when this is included, which will then also give you night/day feedback that can be used to initiate automatic system security level mode changes.

The cost of manufacturing powerful single chip Microcontrollers has dropped significantly. Now affordable devices are available that have high level C programming capabilities, large amounts of memory and 12 bit analogue to digital converter (ADC) inputs with 1 ps conversion times. These devices can have low current consumption (2μΑ) and even lower standby or “sleep” current consumption (10nA).

Rather than using a current transformer, the current measurements can be derived from an inductive pickup coil that couples with the electromagnetic field surrounding the fence wire when a current is flowing through it. The advantage of using this technique is that the fence circuit does not need to be cut. The use of a closed magnetic circuit device is not excluded, as although it does raise some practical installation issues, ultimately it has the potential to provide the most accurate current measurements. A hall-effect device inside the closed magnetic circuit is preferred over a wound coil secondary as this can provide a higher performance, faster response and reduce the size of the Monitor and then ultimately the cost.

Initially the Monitor starts a fence voltage measurement directly after receiving a digital interrupt caused by the rising (or falling) edge of a fence pulse. The current design hardware can trigger a measurement with voltages as low as 200V. Electric fence voltages typically range between 300V - 15,000V. 34 2013273826 23 Dec 2013

Once the monitor has established and locked on to the Energiser pulse it can set up a pulse window. Voltage measurements can then be triggered to commence prior to the arrival of the pulse using the internal Time Base Clock and thus capture the entire pulse. The pulse measurement window can also be automatically extended if the pulse is found not to be completely contained in the window.

Voltage measurements are taken in sample steps at a rate governed by the capabilities of the ADC system and available memory size. The preferred strategy is to use the available RAM (Random Access Memory) size to decide the sample rate. A typical product might take 250 samples at 1ps intervals. Electric fence pulses are always well spaced and there is plenty of post-sampling time available to process the measurements. In most cases the limitation might well be the demand on the power supply stored energy budget. The low current requirements of the latest generation microcontrollers make this less of an issue.

Current measurements will be sampled in exactly the same way as the voltage and over the same window period. Currents over a 100:1 range can be handled comfortably.

The voltage and current measurements together with clock time and other related information can be combined to produce rich collection of secondary derived measurement values including but not restricted to pulse power, pulse energy, average power, pulse duration and historical pulse time trends. These secondary derived measurement values can be important in accessing the safety of the fence at any given time.

Electric fence energisers generally maintain pulses at constant level and form so the Monitor can toggle between voltage and current measurements with each alternate pulse allowing higher sampling rates and the quality of the information derived from the samples can be higher. If both current and voltage measurements are needed to be taken from a single pulse, the Monitor can still be configured to automatically toggle between the two inputs collecting voltage 35 2013273826 23 Dec 2013 and current data at alternate time periods. More critical applications can be addressed using one of the latest microcontrollers that also has a DMA controller and ADC pipelining. This device can allow several ADC processes to run simultaneously and the ADC results are fed directly into memory without the CPU (Central Processing Unit) being involved in the process.

The measurement of battery voltage, temperature, solar charging performance etc. will nearly always be less time critical and measurements of this type can be done generally at any chosen time.

The Security electric fence energiser is designed deliberately with an output voltage performance characteristic that allows the fence pulse voltage to fall when a fence contact load is applied (someone touching the fence). This change in voltage is detected and used to trigger the security alarm. However at the same time the energiser must be capable of supporting a reasonable standing load such as growing vegetation, leaking fence insulators etc. without the fence pulse voltage dropping below a level such that it can not deliver an effective shock. This level is generally thought to be around 2500 volts.

Figure 11 indicates how the voltage might drop when someone contacts the electrified fence wire with their hand. Experiments have shown a human body impedance from hand to foot is typically around 1000 ohms. The safety standards use a lower value of 500 ohms in an attempt to offer an improved margin of safety. The percentage change in voltage will vary with the level of the standing fence load on the fence. This is shown in Figure 11 for a 1 kQ contact. This varies from 25% with an open circuit down to 11% for heavy loads that take the fence voltage down to 2500 V.

Standing fence voltages vary slowly with time, depending on changes caused by the environment, weather, season and age of the installation, whereas fence contact or deliberate fence tampering cause sudden fence voltage changes. A traditional electric fence monitoring alarm system is set simply to activate an alarm if the fence voltage falls below a preset level. This system initially operates 36 2013273826 23 Dec 2013 reliably but as the fence condition deteriorates the standing voltage falls to the set level and the alarm is sounded in error. To maximise the usage period between fence maintenance times and minimise nuisance tripping, the user routinely sets the trip to a low voltage level. This then leads to the system being unable to reliably detect fence contacts and possible security breaches.

One electric fence monitoring technique that can be used takes an average of the measurements over a period and uses this average as a base fence voltage level. Measurements that deviate significantly from the base fence voltage level indicate a possible fence contact or breach. A deviation trip level is set at, for example, 20% and used to trigger an alarm condition.

Figure 11 indicates that using a periodic average voltage value is unreliable. For light loads (25%) the 20% trip level setting may be too low and this can lead to nuisance alarms and for heavy loads the 20% trip level will be too high (11%) and an alarm will not be raised.

In this arrangement the System Energiser characteristic is included in the software algorithm that sets the trip point setting percentage. This minimises false alarms and also maximises the sensitivity under difficult heavily loaded conditions. For example, looking at Figure 11, the deviation trip level could be set for only 10% for a heavily loaded fence at 2500 V and then be adjusted up to 24% for a lightly loaded fence.

General System Points

The electric fence security energiser system described can be installed more easily, more quickly and with less disruption and damage to the user’s premises than the alternative traditional integrated security energiser units. The cost of the installed equipment is similar, thus the final client ends up with a lower overall total job cost. Another secondary advantage provided by the system is that it can also be removed more easily with minimal repair work required to put the user’s premises back to pre-installation condition. 2013273826 23 Dec 2013 37

It will also be understood that, as an alternative, the energiser module may have a transceiver for transmitting and receiving signals to/from any of the monitoring module, control module or remote control unit.

Further, it will be understood that, as an alternative, the energiser module may be in communication with the monitoring module via the electric fence and so will be controlled via signals received at either the monitoring module or energiser module from either or both of the control module or remote control unit. That is, signals are passed between the monitoring module and energiser module using the electric fence as a transmission medium. In this way, only one of the monitoring module and energiser module is required to have a wireless transceiver. Further, the control module or remote may communicate directly with any system device.

Also, it will be understood that the monitoring module and gate switch module may not include a charging system but could be operated using a standard battery or batteries. These batteries could be replaced when the monitoring module indicates to the controller that the battery voltage level has dropped below a predetermined level.

Further, it will be understood that the system described herein may be enhanced by incorporating a communication system that enables the wireless monitoring of other elements, such as doors and gates etc. The system may include security aspects which provide alarms when certain zones are activated. The system can include a keypad to control, activate and deactivate the zones. An Internet connection may be provided to allow messages to be sent by the system to a user, and for a user to control the system. Further, the system may be monitored and controlled using a wireless communication device, such as a PDA or cell phone.

Claims (15)

1. WHAT WE CLAIM IS:

   1. A monitoring module for monitoring pulses applied to an electric fence in an electric fence system that includes an energiser module for applying pulses to an electric fence, wherein the monitoring module is arranged to monitor, within a dynamic time period, the pulses applied to the electric fence and to adjust the dynamic time period until an applied pulse is detected by the monitoring module within the time period.
2. 2. The monitoring module of claim 1 further arranged to synchronise the dynamic time period to the pulse rate of the pulses.
3. 3. The monitoring module of claim 1 further arranged to shift the dynamic time period so it is centered on the detected pulse.
4. 4. The monitoring module of claim 3 further arranged to reduce the dynamic time period after it has been shifted.
5. 5. The monitoring module of claim 1 further arranged to analyse any signals received from the electric fence when the energiser module is not applying pulses to the fence.
6. 6. The monitoring module of claim 5 further arranged to mask the analysed signals received.
7. 7. The monitoring module of claim 1 further arranged to monitor continuous AC signals.
8. 8. The monitoring module of claim 1 further arranged to monitor for AC signals between 50 Hz and 60 Hz.
9. 9. The monitoring module of claim 1 further arranged to monitor for DC signals.
10. 10. A method of monitoring pulses in an electric fence system, the method including the steps of: monitoring an electric fence within a dynamic time period to detect pulses applied to the electric fence and adjusting the dynamic time period until an applied pulse is detected by the monitoring module within the time period.
11. 11. The method of claim 10 further including the step of synchronising the dynamic time period to the pulse rate of the pulses.
12. 12. The method of claim 10 further including the step of shifting the dynamic time period so it is centred on the detected pulse.
13. 13. The method of claim 12 further including the step of reducing the dynamic time period after it has been shifted.
14. 14. The method of claim 10 further including the step of analysing any signals received from the electric fence when the energiser module is not applying pulses to the fence.
15. 15. The method of claim 14 further including the step of masking the analysed signals received.