JP2003344096A - Electric measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent noise currents caused by an AC power source from flowing in the measuring circuit of an electric measuring apparatus which uses the AC power source as a power source, even in an environment where only a power source 2P is available, and grounding is impossible. <P>SOLUTION: The measuring apparatus is provided with a first power storage means 121 and a second power storage means 122 which are used as power sources for the measuring circuit 110, and a charging circuit 130 which charges each storage means 121, 122 by the AC power source E. Charging-side switching means SW1, SW2 and discharge-side switching means SW3, SW4 are changed over properly by a switching control means 140 according to the quantity of the stored electricity of each means 121, 122. The measuring circuit 110 is operated by one of the power storage means, and the other power storage means is charged by the charging circuit 130, and this operation is performed repeatedly. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric measuring instrument driven by an AC power source (including an AC adapter), and more particularly to noise countermeasures when using a power source 2P.

[0002]

2. Description of the Related Art As schematically shown in FIG. 3, an electric measuring instrument is roughly divided into a measuring signal input section 10 and a measuring instrument main body 20. Various sensors or probes for detecting the physical quantity of the object to be measured are connected to the measurement signal input unit 10. In this example, when a temperature sensor S consisting of a thermocouple is connected to the measurement signal input unit 10. Indicates.

That is, the electrical measuring instrument of this example is a temperature measuring instrument, and the measurement signal input section 10 receives a detection signal output from the temperature sensor S by a differential amplifier 11 and A / D-converts the differential output. It is converted into a digital signal by the instrument 12 and given to the measuring instrument body 20.

Although not shown, the measuring device main body 20 has a CP
The measuring device main body 2 is provided with a computing means such as U and a memory, and a display device such as a display and a printer.
0 displays the temperature value of the object to be measured and its displacement amount by processing the measurement signal from the measurement signal input unit 10 in a predetermined manner.

A power supply E is required for the electric measuring instrument,
Most of them, except for some portable ones, are powered from a wall outlet commercial power source (100 VAC). FIG. 3 shows a case where the power supply 2P is used.
Here, the power supply 2P refers to a case where AC power is obtained from a wall outlet (or a power tap) via a power plug having two pins on the hot side and the cold side.

[0006]

In the usual design, the measurement signal input section 10 and the measuring instrument main body 20 are separate boards for the purpose of electrical insulation, and for example, a photocoupler is used for exchanging signals, and a power supply is used. I am going through a transformer.

However, when the power supply 2P is used, the measuring device main body 20 has a potential of about AC50V when viewed from the ground (when AC100V power supply is used). Therefore, even if the measurement signal input unit 10 and the measuring device main body 20 are electrically insulated from each other, for example, a loop in which a current of AC50V flows to the input line of the measurement signal input unit 10 via the coupling capacitance existing in the transformer (see FIG. 3 (see the chain line).

This becomes a noise current and adversely affects the measurement (particularly, it is significantly affected when the temperature sensor S including a thermocouple is used). This noise phenomenon similarly occurs when the AC adapter is used as long as the power source used is the power source 2P. At the time of the power supply 3P, the midpoint of the power supply is dropped to the ground, and the potential of the measuring device main body 20 becomes the same as the ground. Therefore, the influence of noise current is smaller than that in the case of the power supply 2P.

As described above, in an environment in which only the power supply 2P is available, or in an environment in which grounding is not possible, the measurement signal input unit 1
Even if 0 is electrically insulated from the measuring device main body 20, unless the coupling capacitance is zero, a noise current flows on the measurement signal input unit 10 side, and the reliability of measurement is impaired.

Therefore, an object of the present invention is to prevent a noise current due to an AC power supply from flowing in the measuring circuit even in an environment where only the power supply 2P can be obtained or an environment in which grounding is not possible.

[0011]

In order to solve the above problems, the present invention includes a measurement circuit in which a physical quantity of an object to be measured is input as an electric signal, and the input signal is converted into a predetermined parameter and output. In an electric measuring instrument using an AC power source as a power source, first and second power storage means used as a power source for the measurement circuit, a charging circuit for charging each power storage means from the AC power source, and the first power storage means. And charging side switch means for alternately connecting the second storage means to the charging circuit, and discharging side switch means for alternately connecting the first and second storage means to the measurement circuit.
A switch control means for monitoring the amount of electricity stored in each of the electricity storage means, and switching the respective switch means so that the electricity storage means is alternately charged and discharged according to the electricity storage amount. It has a feature.

The present invention includes the following two modes in order to alternately charge and discharge the respective power storage means by the switch control means. In the first aspect, the one storage means whose remaining storage amount has become a predetermined value or less due to discharge is disconnected from the measurement circuit and connected to the charging circuit, and the other storage means is disconnected from the charging circuit. And connect to the above measurement circuit.

As a second aspect, the one storage means which has reached a full storage state by charging is disconnected from the charging circuit and connected to the measuring circuit, and the other storage means is disconnected from the measuring circuit. Connect to the charging circuit.

Each of the storage means may be a secondary battery or a capacitor, but when a capacitor is used, an electric double layer capacitor having a large capacitance is preferable. As a charging method, constant voltage charging is preferable for a secondary battery and constant current charging is preferable for a capacitor.

According to the present invention, the AC power source is used only for charging, and the driving power source for the measuring circuit is obtained from the power storage means, so that the loop of noise current is eliminated, only the power source 2P can be obtained, and it cannot be grounded. Even in the environment
A reliable measurement value is obtained.

Further, since the storage means are charged alternately,
It is also possible to measure for a long time without having to worry about the driving time. The present invention does not exclude the case where the power source 3P is used.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram of an electric measuring device 100 according to the present invention, in which two power storage means 12 used as a power source for a measuring circuit 110 in the measuring device are provided.
1, 122 and the AC power source E to the power storage means 121, 122
And a charging circuit 130 for charging the.

The electrical measuring instrument 100 also includes the measuring signal input section 10 and the measuring instrument main body 20 described above with reference to FIG. 3, but in this case, the measuring circuit 110 includes the measuring signal input section 1
0 and the measuring device main body 20 may be included, or only the measurement signal input unit 10 may be included.

That is, the storage means 121, 122 may be used as a common power source for the measurement signal input section 10 and the measuring device main body 20, or may be used as a dedicated power source for the measurement signal input section 10. The measurement target of the measurement circuit 110 may be voltage, current, resistance, temperature, etc. and is not particularly limited.

In this example, the storage means 121, 122
Since a battery (secondary battery) is used for the battery, a battery 121, 122 will be described below, but a capacitor (preferably an electric double layer capacitor) may be used instead. Further, the AC power source E may be a commercial power source (AC100V).

The batteries 121 and 122 are the charging circuit 13
0 and the measuring circuit 110 are connected in parallel.
That is, the power input sides of the batteries 121 and 122 are connected to the charging circuit 130 via the switches SW1 and SW2 (charge side switches), and the power output sides of the batteries 121 and 122 are connected to the switches SW3 and SW4 (discharge side). It is connected to the measuring circuit 110 via a switch.

The electrical measuring instrument 100 also comprises a switch control means 140 for controlling the switching of the switches SW1 to SW4. In this example, the switch control unit 140 includes a CPU that monitors the voltage (charge storage amount) of the batteries 121 and 122 and outputs a switching signal when the voltage becomes a predetermined value or less.

To explain the operation, as shown in FIG. 1, when the switch SW1 is off and the switch SW3 is on, power is supplied to the measuring circuit 110 from one battery 121, while the switch SW2 is on and the switch SW2 is on. S
It is assumed that W4 is off and the other battery 122 is charged by the charging circuit 130.

In this state, when one of the batteries 121 driving the measuring circuit 110 is exhausted and the remaining voltage becomes less than a predetermined value, the switch control means 140 turns on the switch SW1 and turns off the switch SW3. The charging circuit 1 by disconnecting the battery 121 from the measurement circuit 110
Connect to 30.

At the same time, the switch SW2 is turned off and the switch SW4 is turned on to disconnect the other battery 122 from the charging circuit 130 and connect it to the measuring circuit 110.
By repeating this, one of the batteries always drives the measurement circuit 110.

In the above embodiment, the switch is switched when the remaining voltage of either one of the batteries becomes equal to or less than the predetermined value. However, as another mode,
The switch may be switched when the battery on the charged side is fully charged. The full charge means a state in which the battery is charged up to a rated voltage or a voltage value arbitrarily set by the user.

That is, for example, as shown in FIG. 1, one battery 121 is in a discharged state and the other battery 122 is
Is in a charging state, when the other battery 122 is fully charged, the battery 122 is charged with the charging circuit 1.
The battery 121 is separated from 30 and connected to the measurement circuit 110, and one battery 121 is separated from the measurement circuit 110 and connected to the charging circuit 130. After that, this is repeated.

Regarding the switches, although four switches SW1 to SW4 are used in the above embodiment, as shown in FIG. 2, two-contact selection type switches SWc and SWd are used for both the charging side and the discharging side. By
You can do it with two switches.

Further, in the above embodiment, the switch control means 140 is independently provided, but for example, the charging circuit 130 has a voltage monitoring function for the batteries 121 and 122 and switches SW1 to SW4 (or switches SWc and SW).
It is also possible to provide the switching function of d).

The charging method for the batteries 121 and 122 is generally constant voltage charging, but it is preferable to use constant current charging as the charging method when a capacitor is used as a storage means instead of the battery in terms of charging efficiency.

[0031]

As described above, according to the present invention,
An electric measuring instrument using an AC power source as a power source includes first and second power storage means used as a power source of a measuring circuit, and a charging circuit for charging each power storage means from an AC power source, and each power storage means by a switch control means. The charging-side switching means and the discharging-side switching means are appropriately switched according to the voltage of, and the measuring circuit is driven by either one of the storage means, and the other charging means is charged by the charging circuit repeatedly. Power supply 2
Even in an environment in which only P can be obtained or in an environment in which grounding is not possible, a highly reliable measurement value is obtained by preventing the noise current due to the AC power source from flowing through the measurement circuit, and the storage means is charged alternately. Therefore, it is possible to perform the measurement for a long time without having to worry about the driving time.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of an electric measuring device according to the present invention.

FIG. 2 is a schematic diagram showing another example of a switch used in the above embodiment.

FIG. 3 is a circuit configuration diagram of an electrical measuring device as a conventional example.

[Explanation of symbols]

100 electric measuring instrument 110 measuring circuit 121,122 battery 130 charging circuit 140 switch control means

Claims (5)

[Claims] 1. An electrical measuring instrument, comprising: a physical quantity of an object to be measured as an electric signal, converting the input signal into a predetermined parameter and outputting the electric signal, wherein an AC power source is used as a power source. First and second power storage means used as a power source for the battery, a charging circuit for charging the power storage means from the AC power source, and the first and second power storage means alternately connected to the charging circuit. Charging side switch means,
Discharge side switch means for alternately connecting the first and second power storage means to the measurement circuit, and monitoring the power storage amount of each power storage means, and charging and discharging of each power storage means according to the power storage amount. An electric measuring instrument, comprising: a switch control means for switching each of the above-mentioned switch means so as to be alternately performed. 2. The switch control means disconnects the one power storage means whose remaining power storage amount has become a predetermined value or less by discharging from the measurement circuit and connects the power storage means to the charging circuit, and connects the other power storage means to the above power storage means. The electric measuring instrument according to claim 1, wherein the electric measuring instrument is separated from the charging circuit and is connected to the measuring circuit. 3. The switch control means disconnects the one storage means, which has reached a fully charged state by charging, from the charging circuit and connects the measurement circuit with the other storage means, and disconnects the other storage means from the measurement circuit. The electric measuring instrument according to claim 1, which is connected to the charging circuit. 4. The electric measuring instrument according to claim 1, wherein each of the storage means is a secondary battery. 5. The electric measuring instrument according to claim 1, 2 or 3, wherein each of the storage means is a capacitor.