JP5153374B2 - Clamp sensor output type discrimination method and discrimination device - Google Patents

Description

  The present invention relates to a clamp sensor that detects a current flowing through an electric circuit to be measured via a clamp-type magnetic core and a coil, and in particular, a determination method for determining an output type (voltage output type, current output type) of a clamp sensor. And a discrimination device.

This type of clamp sensor can be classified into a voltage output type and a current output type according to its output type.
Here, FIG. 3 is a block diagram of a voltage output type clamp sensor, FIG. 4 is a block diagram of a current output type clamp sensor, and in these drawings, 11 is an electric circuit to be measured, 21 is a magnetic core, 22 is a coil , 23 is a sensor-side shunt resistor (resistance value is r), and 24 is a diode.

In both the voltage output type and the current output type, a current i (= I / N) obtained by dividing the current I flowing through the measured circuit 11 by the number N of turns of the coil 22 flows in the coil 22.
In the voltage output type clamp sensor shown in FIG. 3, a voltage v (= i × r) obtained by current / voltage conversion of the current i by the shunt resistor 23 is input to a measuring instrument (not shown) such as a wattmeter. A voltage output type clamp sensor is disclosed in Patent Document 1, for example.

  On the other hand, in the current output type clamp sensor shown in FIG. 4, the current i is directly input to the measuring instrument, but depending on the magnitude of the current I, a large open-ended voltage of, for example, several hundred volts appears at both ends of the coil 22. Therefore, the diode 24 is inserted in consideration of safety to prevent an excessive voltage from being output. In this case, the forward voltage of the diode 24 is set to a large value so as not to affect the voltage drop due to the measuring instrument side shunt resistor (not shown) on the input side of the measuring instrument.

Here, FIG. 5 exemplifies general characteristics of the voltage output type and current output type clamp sensors. The input current (current flowing through the circuit to be measured) and the output voltage (in the current output type clamp sensor). , Output terminal open circuit voltage).
In the voltage output type, the output voltage is almost proportional to the input current. In the current output type, when the input current is small, the output voltage is larger than that in the voltage output type, but the input current reaches almost 1A. The output voltage is saturated from the moment.

As described above, the voltage output type and current output type clamp sensors have different output types and characteristics. Therefore, the measuring device that takes these outputs and measures the current, power, etc. of the circuit under test is also the output type of the clamp sensor. It is necessary to use the voltage input type and the current input type properly.
Further, when it is desired to use a single measuring instrument for the voltage output type and current output type clamp sensors, as shown in FIG. 6, a manual changeover switch 31 and a measuring instrument side shunt are provided at the input of the measuring instrument 30. When a resistor 32 (with a resistance value R) is connected and a voltage output type clamp sensor is connected, the changeover switch 31 is connected to the terminal a side in the figure, and a current output type clamp sensor is connected. In this case, by connecting the changeover switch 31 to the terminal b side in the figure, the current in the circuit under measurement is input to the measuring device 30 as a voltage in any case.

JP-A-9-80105 (paragraphs [0002], [0016], etc.)

As shown in FIG. 6, a user who does not have a measuring device 30 whose input type can be switched by the changeover switch 31 and the measuring device-side shunt resistor 32 can be used for the input type of the measuring device or the clamp sensor. Depending on the output type, a suitable type of clamp sensor or measuring instrument must be prepared.
In addition, even when the measuring instrument 30 that can switch the input type as shown in FIG. 6 is owned, it is necessary to manually switch the changeover switch 31 according to the output type of the clamp sensor. In some cases, measurement may be performed without forgetting the switching operation.

In particular, when the voltage output type clamp sensor is connected to the measuring instrument 30 but the current output type clamp sensor is mistakenly connected and the changeover switch 31 is connected to the terminal b side in FIG. As a result of connecting the sensor side shunt resistor 23 of FIG. 3 and the measuring instrument side shunt resistor 32 of FIG. 6 in parallel, the voltage input to the measuring instrument is reduced by these combined resistors.
However, from the input voltage value of the measuring instrument at that time, it is difficult to notice that the changeover operation of the changeover switch 31 is forgotten, and as a result, an erroneous measurement value may be mistaken as a correct value. It was.

  Accordingly, the problem to be solved by the present invention is to automatically and reliably determine the output type of the clamp sensor connected to the measuring instrument, and to obtain an accurate measurement value according to the output type, as well as various types of clamp sensors. Another object of the present invention is to provide a clamp sensor output type discrimination method and discrimination device that eliminates the burden of preparing a measuring instrument.

In order to solve the above-described problem, the output type discrimination method according to claim 1 is configured such that when the current flowing through the circuit to be measured is detected by the clamp sensor and input to the measuring instrument, the clamp sensor is connected between the pair of output terminals. In the output type discrimination method of the clamp sensor for discriminating between the voltage output type in which the sensor side shunt resistor is connected to the current output type in which the sensor side shunt resistor is not connected,
The measuring instrument side shunt resistor that can be connected between the pair of input terminals is provided in the measuring instrument, and the measuring instrument side shunt resistance is input between the input terminal and the first connection state in which the output signal of the clamp sensor is directly input. Provided with a changeover switch for switching between the second connection state for inputting and connecting
With the clamp sensor connected between the input terminals, the changeover switch is switched between the first connection state and the second connection state, and based on the ratio of the input voltage of the measuring instrument measured in each connection state. The output type of the clamp sensor connected between the input terminals is discriminated.

The output type discriminating method according to claim 2 is an output type discriminating method of the clamp sensor according to claim 1,
When the value obtained by dividing the input voltage of the measuring instrument measured in the first connection state by a constant is substantially equal to the input voltage of the measuring instrument measured in the second connection state, the input voltage is connected between the input terminals. The clamp sensor is determined to be a voltage output type, and otherwise determined to be a current output type.

The output type discriminating method according to claim 3 is the clamp sensor output type discriminating method according to claim 2,
When the value obtained by dividing the input voltage of the measuring instrument measured in the first connection state by the first constant is substantially equal to the input voltage of the measuring instrument measured in the second connection state, the sensor-side shunt resistance Is identified as the first resistance value,
When the value obtained by dividing the input voltage of the measuring instrument measured in the first connection state by a second constant is substantially equal to the input voltage of the measuring instrument measured in the second connection state, the sensor-side shunt resistance This resistance value is identified as the second resistance value.

The output type discrimination method according to claim 4 is the clamp sensor output type discrimination method according to any one of claims 1 to 3,
When the output type of the clamp sensor is determined as the voltage output type, the changeover switch is switched so as to realize the first connection state, and when the output type is determined as the current output type, the second connection state is realized.

The output type discriminating apparatus according to claim 5 is configured such that when the current flowing through the circuit to be measured is detected by the clamp sensor and input to the measuring instrument, the sensor-side shunt resistor is connected between the pair of output terminals. In the output type discrimination device of the clamp sensor that discriminates between the voltage output type that is used or the current output type that is not connected to the sensor side shunt resistor,
The measuring instrument is
Measuring instrument side shunt resistor connectable between the pair of input terminals,
A changeover switch that switches between a first connection state in which an output signal of the clamp sensor is directly input and a second connection state in which the measuring instrument side shunt resistor is connected between the input terminals and input;
With the clamp sensor connected between the input terminals, the changeover switch is switched between the first connection state and the second connection state, and based on the ratio of the input voltage of the measuring instrument measured in each connection state. Means for determining the output type of the clamp sensor connected between the input terminals;
It is equipped with.

The output type discriminating device according to claim 6 is the output type discriminating device of the clamp sensor according to claim 5,
Means for switching the changeover switch so as to realize a first connection state when the output type of the clamp sensor is determined as a voltage output type and a second connection state when the output type is determined as a current output type Is.

According to the present invention, for example, the changeover switch is switched by a command from the CPU in the measuring instrument to realize the first connection state and the second connection state, and the ratio of the measuring instrument input voltage in each connection state is calculated. This makes it possible to easily determine the output type of the clamp sensor and start the measurement operation corresponding to each type. For this reason, the current or the like can be measured regardless of the output type of the clamp sensor, and it is not necessary to limit the output type of the clamp sensor by a measuring instrument or to prepare a measuring instrument having a different input type.
According to the invention of claim 3, the resistance value of the shunt resistor of the voltage output type clamp sensor can be identified from the first and second constants corresponding to the first and second connection states. Is possible.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a main part of a measuring instrument 100 such as a wattmeter equipped with an output type discrimination device according to this embodiment.
In FIG. 1, reference numeral 101 denotes a clamp sensor connection terminal to which a voltage output type or current output type clamp sensor (not shown) is connected. This connection terminal 101 is connected to a measuring instrument side shunt via a first changeover switch 102. The resistor 103 (the resistance value is R) and the amplifier circuit 104 are connected.
When the clamp sensor is a voltage output type, the first changeover switch 102 is connected to the terminal a side (referred to as a first connection state) by a connection switching signal 111 from the CPU 107 to be described later. Is input to the amplifier circuit 104, and when the clamp sensor is a current output type, it is connected to the terminal b side (referred to as the second connection state) and the detection voltage by the measuring instrument side shunt resistor 103 is input to the amplifier circuit 104. It has become so.

A detection circuit 105 is connected to the output side of the amplifier circuit 104, and its output is input to the A / D converter 106 and the terminal c of the second changeover switch 109.
A digital signal output from the A / D converter 106 is input to the CPU 107. This CPU 107 performs the original calculation processing of the measuring instrument such as measurement of the detected current by the clamp sensor and measurement of electric power and the control operation of the entire apparatus, and the connection switching signal 111 and the second switching for the first selector switch 102. A function of generating and outputting an output switching signal 112 for the switch 109 is also provided. The CPU 107 is connected to a display 108 for displaying a current measurement value by the clamp sensor, a discrimination result of the output type of the clamp sensor, and the like.
In addition, 110 is an output circuit used when outputting the current measurement value by a clamp sensor to the outside as needed.

Next, the output type discrimination operation of the clamp sensor in this embodiment will be described with reference to the flowchart of FIG.
First, in a state where a voltage output type or current output type clamp sensor is connected to the clamp sensor connection terminal 101, the power source of the measuring instrument 100 is turned on to start the operation.

  First, the CPU 107 in the measuring instrument 100 causes the display 108 to display the current measurement value as 0 A, outputs the output switching signal 112, connects the changeover switch 109 to the terminal d side, and turns off the output (0 V). And At the same time, the CPU 107 assumes that the connected clamp sensor is a voltage input type, and connects the changeover switch 102 to the terminal a side by the connection changeover signal 111 (step S1).

Next, in this state, based on the voltage input via the amplification circuit 104, the detection circuit 105, and the A / D converter 106, the CPU 107 calculates an input voltage corresponding to the current detection value by the clamp sensor as a temporary measurement value. Calculate and acquire as A (step S2).
If the provisional measurement value A does not exceed an arbitrary numerical value (for example, 0.1 mV), the process returns to step S2 (step S3 NO), and if it exceeds, the process proceeds to the next step S4 (step S3 YES).
Here, when the connected clamp sensor is a voltage output type, since the clamp sensor is normally connected to the measuring instrument 100, the temporary measurement value A corresponds to the current detection value by the clamp sensor. When the connected clamp sensor is a current output type, the open end voltage of the clamp sensor is measured, so that the temporary measurement value A is a large value.

Next, the CPU 107 switches the changeover switch 102 to the terminal b side, that is, the current output type clamp sensor side by the connection changeover signal 111 (step S4), and similarly to the above, the voltage corresponding to the current detection value by the clamp sensor is set to the temporary measurement value B. Is calculated and acquired (step S5).
In this case, when the connected clamp sensor is a voltage output type, the sensor side shunt resistor (shunt resistor 23 in FIG. 3) and the measuring instrument side shunt resistor 103 in the measuring instrument 100 are connected in parallel. Therefore, the provisional measurement value B becomes smaller than the provisional measurement value A as described later due to the combined resistance of both. When the connected clamp sensor is a current output type, since the clamp sensor is normally connected to the measuring instrument 100, the temporary measurement value B is normal according to the current detection value by the clamp sensor. Value.

Next, the ratio between the temporary measurement value B and the temporary measurement value A is calculated.
Here, Table 1 shows an example of the specification according to the output type of the clamp sensor.

As shown in Table 1, in the voltage output type clamp sensor (sensors 3, 4 and 5), the resistance value r of the sensor-side shunt resistor 23 is, for example, 1Ω or 10Ω according to the rated current. The resistance value R of the measuring instrument side shunt resistor 103 is, for example, 1Ω.
Explaining these assumptions, after obtaining the temporary measurement value B in step S5 of FIG. 2, the ratio between the temporary measurement value B and the temporary measurement value A is calculated to obtain the output type of the clamp sensor and the voltage. In the case of the output type, it is possible to determine how many Ω the type of clamp sensor is on the sensor side shunt resistance.

Specifically, it is as follows.
That is, if the provisional measurement value B is approximately ½ of the provisional measurement value A (step S6 YES), the sensor-side shunt resistance 23 (r = 1Ω) and the measuring instrument-side shunt resistance 103 (R = 1Ω) Since the combined resistance value is considered to be a result of 0.5Ω, it can be determined that the clamp sensor is a voltage output type and the resistance value r of the sensor-side shunt resistor 23 is 1Ω.

Further, when the temporary measurement value B is not substantially ½ of the temporary measurement value A (NO in step S6), the clamp sensor is a voltage output type, and the resistance value r of the sensor-side shunt resistor 23 is other than 1Ω. That is, it is 10Ω or the clamp sensor is considered to be a current output type.
Therefore, it is determined whether or not the temporary measurement value B is approximately 1/11 of the temporary measurement value A. If it is approximately 1/11 (YES in step S8), the sensor-side shunt resistor 23 (r = 10Ω) is obtained. Since the combined resistance value with the measuring instrument side shunt resistor 103 (R = 1Ω) is considered to be a result of approximately 0.9Ω, the clamp sensor is a voltage output type and the resistance value r of the sensor side shunt resistor 23 is r. Can be determined to be 10Ω.
Here, the constants “2” and “11” in the ratios “1/2” and “1/11” between the temporary measurement value B and the temporary measurement value A described above are the first and second constants in claim 3, respectively. Corresponds to a constant.
If the temporary measurement value B is not substantially 1/11 of the temporary measurement value A (NO in step S8), it can be determined that the clamp sensor is a current output type.

  When branching to the YES side in step S6 or S8 described above, it can be determined that the connected clamp sensor is a voltage output type, and in this case, the changeover switch 102 is connected to the terminal a side by the connection switching signal 111 from the CPU 107. That is, switching to the voltage output type clamp sensor side is performed (step S7). If the branch is made to the NO side in step S8 described above and the clamp sensor is determined to be the current output type, the changeover switch 102 is already connected to the terminal b side, that is, the current output type clamp sensor side. Therefore, step S7 is not executed.

  Thereafter, when the measuring instrument 100 includes the output circuit 110, the output switch signal 112 is switched to the terminal c side by the output switching signal 112 to turn on the output (step S9). Since the output type of the clamp sensor is determined by the above procedure, the measuring device 100 may start the original measurement operation (step S10).

In the above embodiment, the resistance value r of the sensor-side shunt resistor 23 and the resistance value R of the measuring instrument-side shunt resistor 103 are assumed to be specific values, but if these resistance values are other values, the step is performed. Needless to say, the constants in S6 and S8 may be changed.
In addition, although the insertion and removal of the clamp sensor with the power on is basically prohibited, an appropriate sensor recognition key indicating the attachment / detachment state of the clamp sensor is provided in the measuring instrument 100, and the clamp is kept with the power on. When the sensor is removed, the step S1 and subsequent steps may be executed after the user operates this recognition key.

It is a principal part block diagram of the measuring device provided with embodiment of this invention. It is a flowchart which shows the output type discrimination | determination operation | movement by embodiment of this invention. It is a block diagram of a voltage output type clamp sensor. It is a block diagram of a current output type clamp sensor. It is a general characteristic view of a voltage output type and a current output type clamp sensor. It is a block diagram of the input part of the conventional measuring device.

Explanation of symbols

11: Circuit to be measured 21: Magnetic core 22: Coil 23: Sensor-side shunt resistance (resistance value r)
24: Diode 100: Measuring instrument 101: Clamp sensor connection terminal 102: First changeover switch 103: Measuring instrument side shunt resistance (resistance value R)
104: Amplifier circuit 105: Detection circuit 106: A / D converter 107: CPU
108: Display 109: Second changeover switch 110: Output circuit 111: Connection changeover signal 112: Output changeover signal

Claims (6)

When the current flowing through the circuit to be measured is detected by the clamp sensor and input to the measuring instrument, the clamp sensor is a voltage output type in which a sensor side shunt resistor is connected between the pair of output terminals, or the sensor side In the clamp sensor output type discriminating method for discriminating whether the current output type is not connected to a shunt resistor,
The measuring instrument side shunt resistor that can be connected between the pair of input terminals is provided in the measuring instrument, and the measuring instrument side shunt resistance is input between the input terminal and the first connection state in which the output signal of the clamp sensor is directly input. Provided with a changeover switch for switching between the second connection state for inputting and connecting
With the clamp sensor connected between the input terminals, the changeover switch is switched between the first connection state and the second connection state, and based on the ratio of the input voltage of the measuring instrument measured in each connection state. A method of discriminating an output type of a clamp sensor, characterized by discriminating an output type of a clamp sensor connected between input terminals. In the clamp sensor output type discrimination method according to claim 1,
When the value obtained by dividing the input voltage of the measuring instrument measured in the first connection state by a constant is substantially equal to the input voltage of the measuring instrument measured in the second connection state, the input voltage is connected between the input terminals. Discriminating the clamp sensor as a voltage output type,
In other cases, it is determined as a current output type, and a clamp sensor output type determination method. In the clamp sensor output type discrimination method according to claim 2,
When the value obtained by dividing the input voltage of the measuring instrument measured in the first connection state by the first constant is substantially equal to the input voltage of the measuring instrument measured in the second connection state, the sensor-side shunt resistance Is identified as the first resistance value,
When the value obtained by dividing the input voltage of the measuring instrument measured in the first connection state by a second constant is substantially equal to the input voltage of the measuring instrument measured in the second connection state, the sensor-side shunt resistance A method of discriminating an output type of a clamp sensor, wherein the resistance value of the clamp sensor is identified as a second resistance value. In the output type discrimination method of a clamp sensor given in any 1 paragraph of Claims 1-3,
When the output type of the clamp sensor is determined to be a voltage output type, the changeover switch is switched so that the first connection state is realized, and when the output type is determined to be a current output type, the second connection state is realized. To identify the output type of the clamp sensor. When the current flowing through the circuit to be measured is detected by the clamp sensor and input to the measuring instrument, the clamp sensor is a voltage output type in which a sensor side shunt resistor is connected between the pair of output terminals, or the sensor side In the output type discrimination device of the clamp sensor for discriminating whether the current output type is not connected to the shunt resistor,
The measuring instrument is
Measuring instrument side shunt resistor connectable between the pair of input terminals,
A changeover switch that switches between a first connection state in which an output signal of the clamp sensor is directly input and a second connection state in which the measuring instrument side shunt resistor is connected between the input terminals and input;
With the clamp sensor connected between the input terminals, the changeover switch is switched between the first connection state and the second connection state, and based on the ratio of the input voltage of the measuring instrument measured in each connection state. Means for determining the output type of the clamp sensor connected between the input terminals;
An output type discrimination device for a clamp sensor, comprising: In the clamp sensor output type discrimination device according to claim 5,
Means for switching the changeover switch so as to realize a first connection state when the output type of the clamp sensor is determined as a voltage output type and a second connection state when the output type is determined as a current output type A clamp sensor output type discriminating apparatus.

Images