JP5301081B2 - Double-insulated electrical measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical measuring instrument capable of safely measuring a high voltage and a high current in spite of its small size, of evading danger of electric shock, and of achieving safety standards. <P>SOLUTION: In the double insulated electrical measuring instrument, the portion from a measuring input terminal of a voltage system up to a circuit 3 on the primary side of voltage is connected with a linear circuit 10 having a basic insulation function; the portion from the circuit 3 up to a secondary side circuit 5 connected to a data output terminal is configured of a linear circuit 11 having a basic insulation function, and the portion from a circuit 4 on the primary side of current connected to a measuring input terminal of a current system up to the circuit 3 is connected with a linear circuit 12 having a basic insulation function. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to an electrical measuring instrument such as a voltmeter, ammeter, wattmeter and the like that requires double insulation that satisfies safety standards.

  Since various types of electrical measuring devices may cause an electric shock when they are touched directly or indirectly, insulation standards are defined as safety standards by Japanese Industrial Standards (JIS standards) or IEC standards.

  For example, in the case of a wattmeter, the voltage primary side circuit and current primary side circuit that are input of measured power, the input voltage and current are processed to calculate the effective value and effective power of the voltage and current, and are recorded through the data output terminal. There is a secondary circuit that outputs to a meter or a display device. The voltage primary side circuit or the current primary side circuit and the secondary side circuit constitute a linear circuit, so that output power corresponding to the voltage input or current input can be obtained.

  When the measured power is relatively large, the voltage primary side circuit or current primary side circuit is insulated by providing an insulating cover or taking a creepage distance or a spatial distance as a part that is electrically shocked when touched by a person. However, the data output terminal connected to the secondary circuit may be touched by a person. Therefore, double insulation is required according to safety standards between the voltage primary circuit or current primary circuit and secondary circuit.

  According to Non-Patent Document 1, double insulation is considered to be insulation composed of both basic insulation and reinforcing insulation. Basic insulation is an insulation that provides protection against electric shock and, if broken, can create a risk of electric shock. The reinforced insulation is an independent insulation provided in addition to the basic insulation to provide protection against electric shock when the basic insulation breaks down. Since basic insulation requires stricter insulation than reinforced insulation, the combination of basic insulation and basic insulation can also satisfy double insulation standards. In addition to this, reinforced insulation is one that has a dielectric strength equivalent to double insulation.

  Examples of the insulating device that constitutes the linear circuit include a transformer, a photocoupler, and a resistor. Some devices are recognized as equivalent to double insulation. For example, a lead wire is double insulated if it is wrapped on a vinyl coating. In the transformer, if the bobbin is insulated and a vinyl-coated wire is used for the winding, insulation equivalent to double insulation can be obtained with one device. Patent Document 1 shows an example in which basic insulation is applied to a bobbin. If vinyl-coated wire is used for the primary winding and vinyl-coated wire is also used for the secondary winding, double insulation is obtained. Many photocouplers satisfy the standard for basic insulation, but few are recognized as equivalent to double insulation in a single device, and the withstand voltage is not so large.

  In safety standards for power meters, double insulation is required. For example, as shown in FIG. 5, double insulation is required between the voltage primary circuit 3 and the secondary circuit 5, and double insulation is also required between the current primary circuit 4 and the secondary circuit 5. If there is double insulation between the input terminal and the secondary circuit, safety is maintained, so insulation between the voltage primary circuit 3 and the current primary circuit 4 is not required and is also required by the standards. Absent.

  FIG. 6 shows an example in which the differential amplifier 13 is used in the voltage primary circuit, and double insulation is completed only by impedance. This impedance is also called a protective impedance, and the value of the impedance is set so as to limit the current flowing through the voltage primary circuit that is in front of the secondary circuit to a certain level or less.

According to the standard, the protective impedance corresponding to double insulation is an impedance that keeps the current value within 0.5 mA. The protective impedance corresponding to basic insulation is an impedance that keeps the current value within 3.5 mA. For example, when constructing protective impedance equivalent to double insulation at operating voltage U = 300 [V], Z = U / I = 300 [V] /0.5 [mA] = 600 [kΩ]
It becomes. Even in a single failure state in which one resistor fails and is short-circuited, the function of the protective impedance must be fulfilled, so two or more resistors on one side of the differential amplifier 13 are required. In the illustrated example, n impedances 10R ₁ ... 10R _n are connected in series. If one of the resistors is short-circuited on each side, the required resistance value R of the resistor is R = 3U / 2I = (3 × 300 [V]) / (2 × 0.5 [mA]) = 900 [kΩ]
It becomes. However, since it is necessary to determine the number of resistors and the resistance value so as to satisfy the rated power specifications of the resistor, for safety reasons, a commercially available wattmeter has a resistor of 200 [kΩ] on one side. A total of 12 pieces are used.

JIS C1010-1 JP-A-5-190354

  As described above, the conventional electric measuring device is very expensive because it avoids the risk of electric shock and achieves double insulation according to safety standards. Moreover, in order to secure a creepage distance and a space distance, it is inevitable that the apparatus becomes large.

  The present invention has been made to solve the above-described problems, and is capable of safely measuring a measurement object that is high in voltage while being small, avoids the risk of electric shock, and achieves safety standards. The purpose is to provide a measuring instrument.

In order to achieve the above object, the double-insulated electric measuring instrument according to claim 1 of the present invention is provided with double insulation between a measurement input terminal and a data output terminal. In the electrical measuring instrument, the line from the measurement input terminal of the voltage system to the voltage primary side circuit is connected by a linear circuit having a basic insulation function, and from the voltage primary side circuit to the secondary side circuit connected to the data output terminal. Consists of a linear circuit having a basic insulation function, and the current primary circuit connected to the measurement input terminal of the current system to the voltage primary circuit are connected by a linear circuit having a basic insulation function ,
The linear circuit having the basic insulation function between the measurement input terminal of the voltage system and the voltage primary side circuit is a protective impedance that does not include a transformer,
A linear circuit having a basic insulation function configured between the voltage primary circuit and the secondary circuit described above is a circuit in which a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit,
The linear circuit having the basic insulation function configured between the current primary side circuit and the voltage primary side circuit is a circuit in which a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit,
The secondary side circuit is a circuit that calculates an electrical measurement value from the voltage input from the measurement input terminal of the voltage system and the current input from the measurement input terminal of the current system and outputs it through the data output terminal. It is characterized by that.

Similarly, the double-insulated electrical measuring device according to claim 2 of the present invention is the one according to claim 1, wherein the voltage primary circuit is downstream of the measurement input terminal of the voltage system. The primary current side circuit is a circuit including an amplifier provided downstream of a measurement input terminal of the current system .

Further, a double-insulated multi-channel electrical measuring device according to claim 3 of the present invention, which has been made to achieve the above object, includes a voltage system from a measurement input terminal to a voltage primary side circuit. Are connected by a linear circuit having a basic insulation function, and the voltage from the voltage primary side circuit to the secondary side circuit connected to the data output terminal is composed of a linear circuit having a basic insulation function, from the first channel to the m-th channel. Between the current input circuit connected to each measurement input terminal of the current system and the voltage primary circuit is connected by a linear circuit having a basic insulation function, and from the voltage primary circuit to the secondary circuit connected to the data output terminal. Is composed of a linear circuit with basic insulation function for each channel ,
The linear circuit having the basic insulation function between the measurement input terminal of the voltage system and the voltage primary side circuit is a protective impedance that does not include a transformer,
A linear circuit having a basic insulation function configured between the voltage primary circuit and the secondary circuit described above is a circuit in which a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit,
A linear circuit having a basic insulation function formed between the current input circuit connected to each measurement input terminal of the current system from the first channel to the m-th channel to the voltage primary side circuit is converted from analog to digital. It is a circuit where a digital photocoupler is connected to the subsequent stage of the circuit,
The secondary circuit calculates an electrical measurement value from the voltage input from the measurement input terminal of the voltage system and the current input from the measurement input terminal of the current system from the first channel to the m-th channel. wherein the circuit der Rukoto for output through the data output terminal.

Similarly, the double-insulated multi-channel electrical measuring device according to the invention of claim 4 is a linear having a basic insulation function from the measurement input terminal of the voltage system of the first channel to the voltage primary circuit. The voltage input circuit connected to each measurement input terminal of the voltage system after the second channel and the voltage primary side circuit is connected by a linear circuit having a basic insulation function, and is connected from the voltage primary side circuit. Up to the secondary side circuit connected to the data output terminal is composed of a linear circuit having a basic insulation function for each channel ,
The linear circuit having a basic insulation function from the measurement input terminal of the voltage system of the first channel to the voltage primary side circuit is a protective impedance not including a transformer,
A linear circuit having a basic insulation function formed between the voltage input circuit connected to each measurement input terminal of the voltage system after the second channel and the voltage primary side circuit is provided at the subsequent stage of the analog / digital conversion circuit. A circuit to which a digital photocoupler is connected,
A linear circuit having a basic insulation function configured for each channel is connected between the voltage primary side circuit and the secondary side circuit connected to the data output terminal, and a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit. Circuit
The secondary circuit, wherein the circuit der Rukoto which calculates and outputs the electrical measurements from the voltage input from the measuring input terminal of the voltage lines of the respective channels through the data output terminal.

  Conventionally, in order to achieve double insulation of voltage system, current system and two systems, a combination of basic insulation and reinforced insulation, or a combination of basic insulation and basic insulation, was required separately for voltage system and current system. . However, the electrical measuring instrument according to the present invention can achieve double insulation in both the voltage system and the current system by combining three basic insulations. Therefore, conventionally, the circuit configuration is simple, the number of parts is reduced, and the device is small and inexpensive as compared with the electrical measuring device.

  In particular, in a multi-channel electrical measuring device, a large number of double insulations are required, and the effect of reducing the number of components according to the present invention is even greater.

  Examples of the present invention will be described below in detail with reference to the drawings. However, the scope of the present invention is not limited to these examples.

  FIG. 1 is a single line diagram showing a schematic block circuit of an embodiment of a double-insulated electrical measuring instrument to which the present invention is applied. The circuit of this electrical measuring instrument reaches from the voltage input terminal through the basic insulation device 10 to the voltage primary circuit 3, and further through the basic insulation device 11 from the secondary circuit 5 to the data output terminal to the display device (not shown). It reaches. On the other hand, the current input terminal reaches the basic insulation device 12 through the current primary circuit 4, and is introduced from the basic insulation device 12 into the voltage primary circuit 3.

  Therefore, since the two basic insulations of the basic insulation device 10 and the basic insulation device 11 are inserted between the voltage input terminal and the data output terminal, double insulation is completed. In addition, since two basic insulations, the basic insulation device 12 and the basic insulation device 11, are inserted between the current input terminal and the data output terminal, double insulation is completed.

FIG. 2 shows a specific part of the block circuit of FIG. 1 in a specific double-line diagram. An impedance 10R, which is the basic insulating device 10 of FIG. 1, is connected to the voltage input terminal. In the illustrated example, n impedances 10R ₁ ... 10R _n are connected in series in the illustrated example, but the impedance 10R can be used alone because it is one basic insulation. The impedance 10R is connected to the differential amplifier 13 corresponding to the voltage primary side circuit 3. The differential amplifier 13 is connected to the photocoupler 14 via the amplifier 16 and the analog / digital conversion circuit 15. A photocoupler 14 corresponding to the basic insulation device 11 in FIG. 1 takes basic insulation. A digital signal can be output from the photocoupler 14.

The current input terminal is connected to a current detection resistor 7 corresponding to the current primary circuit 4 of FIG. The current detection resistor 7 is connected to the photocoupler 14 via the amplifier 16 and the analog / digital conversion circuit 15. Basic insulation is obtained by the function of the photocoupler 14 (corresponding to the basic insulation device 12 in FIG. 1).

  The secondary circuit 5 connected to the basic insulation device 11 is a known circuit such as a circuit that calculates an effective value and an effective power from input voltage and current. The data output terminal of the secondary circuit 5 is connected to a recorder, a display circuit, or an input / output interface of a personal computer, such as a USB or RS232C.

FIG. 3 is a single line diagram showing a schematic block circuit of an apparatus of a multi-channel system in which a measurement system is another embodiment of a double-insulated electric measuring instrument to which the present invention is applied. In this multi-channel electrical measuring instrument, the voltage input is one channel and the current input is channels CH1, CH2,..., CHm. The voltage input passes through the primary insulation device 10, passes through the voltage primary circuit 3, and further passes through the basic insulation device 11 to reach the data output terminal from the secondary circuit 5. Current input CH1, CH2, ..., CHm are each current input circuit _{7 1,} 7 2, ..., through _{7 m,} basic insulation device _{12 1,} 12 2, ..., the voltage through the 12 _m It passes through the primary side circuit 3. Further, each basic insulation device _{11 1,} 11 2, ..., extending from the secondary circuit 5 through the 11 _m to the data output terminal. The current input circuits 7 ₁ , 7 ₂ ,..., 7 _m are current detection resistors, for example, and do not necessarily constitute an insulating device.

In such a configuration, each channel of the current input CH1~CHm in a multi-channel electrical measuring instrument of FIG. 3 between the voltage input terminal to the data output terminal, basic insulation device 12 _{1 to m} and foundation insulation device 11 _{1 Since} two basic insulations of _{~ m} are inserted, double insulation is completed.

FIG. 4 is a schematic block circuit diagram of another embodiment of a double-insulated electrical measuring device to which the present invention is applied. In this multi-channel electrical measuring instrument, the voltage input has channels CH1, CH2,..., CHm. The voltage input CH1 passes through the basic insulation device 10 and the voltage primary side circuit 3, and further passes through the basic insulation device 11 to reach the data output terminal from the secondary side circuit 5. Voltage input CH2, CH3, ..., CHm are each voltage input circuit _82, 8 3, ..., through _{8 m,} basic insulation device _{12 1,} 12 2, ..., the voltage through the 12 _m It passes through the primary side circuit 3. Further, each basic insulation device _{11 2,} 11 3, ..., extending from the secondary circuit 5 through the 11 _m to the data output terminal. The voltage input circuits 8 ₂ , 8 ₃ ,..., 8 _m are, for example, current limiting resistors (protective resistors), but do not constitute an insulating device and do not necessarily satisfy safety standards by themselves. .

In this configuration, the voltage input CH1 in the multi-channel electrical measuring instrument of FIG. 4, between the voltage input terminal to the data output terminal, the two basic insulation of basic insulation device 10 and the underlying insulating device 11 ₁ is inserted So double insulation is complete. Each channel of the voltage inputs _CH2 to _CHm has two basic insulations of the basic insulation devices ₁₂₁₂ to _m and the basic insulation devices _{112 to m} inserted between the voltage input terminal and the data output terminal. Heavy insulation is complete.

  In the above-described embodiment, a circuit using a linear characteristic in which an analog / digital conversion circuit and a photocoupler are combined is shown as a linear circuit having a basic insulation function, but this combination can be replaced with an analog photocoupler. Moreover, a transformer and other circuits can be used as a linear circuit having a basic insulation function.

  In addition, the present invention can be similarly applied to any electric measuring device such as a wattmeter, a voltmeter, an ammeter, and a combination thereof. It can also be applied to a memory high coder.

1 is a schematic block circuit diagram of an embodiment of a double-insulated electrical measuring device to which the present invention is applied.

It is a circuit diagram of the principal part of the double-insulated electric measuring device to which the present invention is applied.

FIG. 6 is a schematic block circuit diagram of another embodiment of a double-insulated electrical measuring instrument to which the present invention is applied, in which a measurement system is a multi-channel device.

FIG. 6 is a schematic block circuit diagram of a multi-channel device in which the measurement system is still another embodiment of the double-insulated electric measuring device to which the present invention is applied.

It is a schematic block circuit diagram of a conventional double-insulated electrical measuring instrument.

It is a circuit diagram of the principal part of the conventional double insulated electrical measuring instrument.

Explanation of symbols

3 is a voltage primary side circuit, 4 is a current primary side circuit, 5 is a secondary side circuit, 7 is a current detection resistor, 7 ₁ , 7 ₂ ,..., 7 _m are current input circuits, 8 ₁ , 8 ₂ , · · ·, _{8 m} is the voltage input _{circuit, 10,11,11 1, 11 2, ···} , 11 m, 12 1, 12 2, ···, 12 m is basic insulation devices, 10R impedance, 13 Is a differential amplifier, 14 is a photocoupler, 15 is an analog / digital conversion circuit, and 16 is an amplifier.

Claims (4)

In the electrical measurement equipment in which double insulation is applied between the measurement input terminal and the data output terminal, the connection from the measurement input terminal of the voltage system to the voltage primary side circuit is connected by a linear circuit having a basic insulation function, The voltage primary side circuit to the secondary side circuit connected to the data output terminal is composed of a linear circuit having a basic insulation function, and the basis from the current primary side circuit connected to the measurement input terminal of the current system to the voltage primary side circuit is the basis. Connected by a linear circuit with insulation function ,
The linear circuit having the basic insulation function between the measurement input terminal of the voltage system and the voltage primary side circuit is a protective impedance that does not include a transformer,
A linear circuit having a basic insulation function configured between the voltage primary circuit and the secondary circuit described above is a circuit in which a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit,
The linear circuit having the basic insulation function configured between the current primary side circuit and the voltage primary side circuit is a circuit in which a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit,
The secondary side circuit is a circuit that calculates an electrical measurement value from the voltage input from the measurement input terminal of the voltage system and the current input from the measurement input terminal of the current system and outputs it through the data output terminal. A double-insulated electrical measuring instrument. The voltage primary side circuit is a circuit including an amplifier provided downstream of the measurement input terminal of the voltage system, and the current primary side circuit includes an amplifier provided downstream of the measurement input terminal of the current system. The double-insulated electrical measuring device according to claim 1, wherein the electrical measuring device is a circuit. A linear circuit having a basic insulation function is connected from the measurement input terminal of the voltage system to the voltage primary side circuit by a linear circuit having a basic insulation function, and from the voltage primary circuit to the secondary side circuit connected to the data output terminal. The current input circuit connected to each measurement input terminal of the current system from the first channel to the m-th channel to the voltage primary circuit is connected by a linear circuit having a basic insulation function, and the voltage primary From the side circuit to the secondary side circuit connected to the data output terminal is composed of a linear circuit having a basic insulation function for each channel ,
The linear circuit having the basic insulation function between the measurement input terminal of the voltage system and the voltage primary side circuit is a protective impedance that does not include a transformer,
A linear circuit having a basic insulation function configured between the voltage primary circuit and the secondary circuit described above is a circuit in which a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit,
A linear circuit having a basic insulation function formed between the current input circuit connected to each measurement input terminal of the current system from the first channel to the m-th channel to the voltage primary side circuit is converted from analog to digital. It is a circuit where a digital photocoupler is connected to the subsequent stage of the circuit,
The secondary circuit calculates an electrical measurement value from the voltage input from the measurement input terminal of the voltage system and the current input from the measurement input terminal of the current system from the first channel to the m-th channel. double insulated multichannel electrical measuring instrument, wherein the circuit der Rukoto for output through the data output terminal. The voltage from the measurement input terminal of the voltage system of the first channel to the voltage primary circuit is connected by a linear circuit having a basic insulation function, and the voltage from the voltage input circuit connected to each measurement input terminal of the voltage system of the second and subsequent channels. The circuits up to the primary circuit are each connected by a linear circuit having a basic insulation function, and the voltage from the primary circuit to the secondary circuit connected to the data output terminal is composed of a linear circuit having a basic insulation function for each channel. Tei Te,
The linear circuit having a basic insulation function from the measurement input terminal of the voltage system of the first channel to the voltage primary side circuit is a protective impedance not including a transformer,
A linear circuit having a basic insulation function formed between the voltage input circuit connected to each measurement input terminal of the voltage system after the second channel and the voltage primary side circuit is provided at the subsequent stage of the analog / digital conversion circuit. A circuit to which a digital photocoupler is connected,
A linear circuit having a basic insulation function configured for each channel is connected between the voltage primary side circuit and the secondary side circuit connected to the data output terminal, and a digital photocoupler is connected to the subsequent stage of the analog / digital conversion circuit. Circuit
The secondary circuit has been double insulation, characterized in circuit der Rukoto which calculates and outputs the electrical measurements from the voltage input from the measuring input terminal of the voltage lines of the respective channels through the data output terminal Multi-channel electrical measuring instrument.

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