JP2009192295A - Method and apparatus for discriminating output type of clamp sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a measurement value exactly by reliably and automatically discriminating an output type of a clamp sensor connected with a measuring instrument, and to eliminate the burden of preparing various types of clamp sensors and measuring instruments. <P>SOLUTION: In a discriminating method which discriminates the output type (voltage output type, current output type) of the clamp sensor used for detecting current flowing in a conductive path to be measured, a selecting switch is disposed at the measuring instrument, which selects a first connection state to directly input an output signal of the clamp sensor or a second connection state of connecting an instrument-side shunt resistor between input terminals in order to carry out the input operation, and then the selecting switch is operated to select the first connection state while the clamp sensor is connected between the input terminals, and an input voltage of the measuring instrument is measured at the timing of supplying constant current from the measuring instrument to the clamp sensor, thereby discriminating the output type of the clamp sensor. <P>COPYRIGHT: (C)2009,JPO&INPIT

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. 5 is a block diagram of a voltage output type clamp sensor, FIG. 6 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, and 22 is a coil. , 23 is a sensor-side shunt resistor (resistance value is r), and 24 is a protective 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. 5, 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. 6, 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, in consideration of safety, the protective diode 24 is inserted to prevent an excessive voltage from being output. In this case, the forward voltage of the protective 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. 7 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 correspond to a voltage output type and current output type clamp sensor by a single measuring instrument, as shown in FIG. 8, 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. 8, 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.
Further, even when the measuring instrument 30 that can switch the input type as shown in FIG. 8 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 and the current output type clamp sensor is mistakenly connected and the changeover switch 31 is connected to the b-side terminal in FIG. As a result of connecting the sensor side shunt resistor 23 of FIG. 5 and the measuring instrument side shunt resistor 32 of FIG. 8 in parallel, the voltage input to the measuring instrument 30 is reduced by these combined resistances. However, from the input voltage value of the measuring instrument 30 at that time, it is difficult to notice that the switching operation of the changeover switch 31 is forgotten, and as a result, an erroneous measurement value may be mistaken as a correct value. there were.

  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,
With a clamp sensor connected between a pair of input terminals of the measuring instrument, a constant current is supplied from the measuring instrument to the clamp sensor, and the input voltage of the measuring instrument at that time is measured to determine the output type of the clamp sensor. To do.

The output type discriminating method according to claim 2 is the output type discriminating method according to claim 1, wherein the measuring instrument is provided with a measuring instrument side shunt resistor connectable between its input terminals, and the output signal of the clamp sensor. A changeover switch that switches between a first connection state that directly inputs the second connection state that is input by connecting the measuring instrument side shunt resistor between the input terminals,
A constant current is supplied from the measuring instrument to the clamp sensor via the changeover switch switched to the first connection state.

The output type discriminating method according to claim 3 is the output type discriminating method according to claim 1 or 2,
A plurality of types of voltage output type clamp sensors having different resistance values of the sensor-side shunt resistors are discriminated from the input voltage of the measuring instrument when a constant current is supplied to the clamp sensor.

In the output type discriminating device according to claim 4, 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 to the sensor-side shunt resistor between the pair of output terminals. In the output type discriminating device of the clamp sensor for discriminating whether the voltage output type to which the sensor is connected or the current output type to which the sensor side shunt resistor is not connected,
The measuring instrument is
A means for supplying a constant current to the clamp sensor with the clamp sensor connected between the pair of input terminals, a means for measuring the input voltage of the measuring instrument with the constant current supplied, and a measured input voltage And means for discriminating the output type of the clamp sensor.

The output type discriminating apparatus according to claim 5 is the clamp sensor output type discriminating apparatus according to claim 4,
A plurality of types of voltage output type clamp sensors having different resistance values of the sensor-side shunt resistors are discriminated from the measured input voltages.

According to the present invention, it is possible to easily determine the output type of the clamp sensor based on the input voltage when a constant current is supplied from the measuring instrument to the clamp sensor, and to 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.
Moreover, according to the invention which concerns on Claim 3 or 5, it is also possible to discriminate | determine the various voltage output type clamp sensors from which the resistance value of sensor side shunt resistance is various.

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 second changeover switch 104 are connected.
When the clamp sensor is a voltage output type, the first changeover switch 102 is connected to a terminal a (referred to as a first connection state) by a switching signal 121 from the CPU 110 to be described later. When the clamp sensor is a current output type, the voltage detected by the measuring instrument side shunt resistor 103 is referred to as the second changeover switch 104. To be input.

The second changeover switch 104 includes a terminal d connected to the constant current circuit 105 and a terminal c connected to the terminal f of the third changeover switch 106, and a terminal c is received by a changeover signal 122 from the CPU 110. It can be switched to the side or d side.
In addition to the terminal f, the third changeover switch 106 is provided with a terminal e that is connected to one of the clamp sensor connection terminals 101 and to which an output type confirmation signal 125 of the clamp sensor is transmitted. The circuit 107 is connected. The third selector switch 106 can be switched to the terminal e side or the f side by a switching signal 123 from the CPU 110.

  The detection circuit 108 is connected to the output side of the amplifier circuit 107, and its output is input to the A / D converter 109 and the terminal g of the fourth changeover switch 112, and the terminal h of the changeover switch 112 is grounded. The fourth changeover switch 112 can be switched to the terminal g side or the h side by a switching signal 123 from the CPU 110.

  A digital signal output from the A / D converter 109 is input to the CPU 110. The CPU 110 performs calculation processing inherent to the measuring instrument such as measurement of a detection current (voltage obtained by converting the current) by the clamp sensor and measurement of electric power, and control operation of the entire apparatus, as well as each changeover switch 102, 104, 106, 112 also has a function of generating and outputting switching signals 121 to 124 for 112. The CPU 110 is connected to a display 113 for displaying a current measurement value by the clamp sensor, a discrimination result of the output type of the clamp sensor, and the like.

Reference numeral 111 denotes a sensor detection button that is artificially pressed when a voltage output type or current output type clamp sensor is connected to the clamp sensor connection terminal 101. Instead of the sensor detection button 111, it may be mechanically detected that the BNC connector which is an output terminal of the clamp sensor is connected to the clamp sensor connection terminal 101, and a signal may be input to the CPU 110.
Furthermore, 114 is an output circuit used when outputting the current measurement value by the 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 110 in the measuring instrument 100 causes the display 113 to display the current measurement value as 0 A, outputs a switching signal 124, connects the changeover switch 112 to the terminal h, and turns the output OFF (0 V). To do. At the same time, the CPU 110 connects the changeover switch 104 to the terminal c side by the changeover signal 122 to make it possible to detect the output signal of the clamp sensor (step S1).

Next, in this state, it is determined whether or not the sensor detection button 111 is pressed (step S2).
If it is confirmed that the sensor detection button 111 is pressed (step S2 YES), the subsequent processing is executed to determine the output type of the clamp sensor. That is, the CPU 110 executes a switching operation of the switches 102, 104, and 106 in the next step using a signal generated when the sensor detection button 111 is turned on as a trigger.

  That is, the first changeover switch 102 is connected to the terminal a on the voltage output type clamp sensor side by the change signal 121 from the CPU 110. Further, the second changeover switch 104 is connected to the terminal d side by the changeover signal 122, and a constant DC current is supplied from the constant current circuit 105 to the clamp sensor, and the third changeover switch 106 is connected to the terminal e by the changeover signal 123. The output type confirmation signal 125 from the clamp sensor can be input to the amplifier circuit 107 (step S3).

  At this time, a constant current is supplied to the clamp sensor from the constant current circuit 105 via the changeover switches 104 and 102. For this reason, as shown in FIGS. 5 and 6, the voltage output type clamp sensor in which the sensor-side shunt resistor 23 is connected to both ends of the coil 22 and the current output type clamp sensor in which the shunt resistor is not connected are used. Since the combined resistance between the output terminals is different, the voltage input to the measuring instrument 100 (amplifier circuit 107) as the output type confirmation signal 125 becomes a different value depending on the output type of the clamp sensor.

Paying attention to the above points, the CPU 110 measures the voltage (output type confirmation signal 125) input via the amplifier circuit 107, the detector circuit 108, and the A / D converter 109 (step S4), and determines the voltage value. Based on this, the output type of the clamp sensor is specified (step S5).
Here, Table 1 shows an example of the specification according to the output type of the clamp sensor, and Table 2 shows the case where the resistance between the output terminals of the clamp sensors 1 to 6 in Table 1 and DC 1 mA are supplied between the output terminals. The output voltage is shown.

As shown in Table 1, in the voltage output type clamp sensor (sensors 3, 4, 5, 6), the resistance value r of the sensor-side shunt resistor 23 is, for example, 1Ω or 10Ω depending on the rated current.
Further, as is apparent from Table 2, the current output type clamp sensor in which the winding resistance by the coil is dominant as the output inter-terminal resistance, and the voltage in which the output inter-terminal resistance is a combined resistance of the winding resistance and the shunt resistance. The output type clamp sensor has a significant difference in output voltage when supplying a constant current.
Therefore, the output voltage of the clamp sensor input to the measuring instrument 100 as the output type confirmation signal 125 is measured, and the CPU 110 compares the measured voltage with a predetermined threshold value, so that the connected clamp sensor is a voltage output type. Whether it is a current output type or not can be determined.

When the output type of the clamp sensor is determined in this way, a changeover signal 121 is output from the CPU 110 according to the output type, so that in the case of the voltage output type, the changeover switch 102 is set to the terminal a side (as it is), and the current output type. In this case, it is connected to the terminal b side. At the same time, the changeover switch 104 is switched to the terminal c side by the changeover signals 122 and 123 and the changeover switch 106 is switched to the terminal f side so that the output signal of the clamp sensor can be measured.
If the measuring instrument 100 includes the output circuit 114, the changeover switch 112 is switched to the terminal g side by the changeover signal 124, and the output is turned on (step S6).
Thereafter, the measuring device 100 may start the original measurement operation (step S7).

  In the voltage output type clamp sensor, since the winding resistance of the coil and a shunt resistor generally having a smaller value than the winding resistance are connected in parallel, the combined resistance value of both is the resistance value of the shunt resistor. Become dominant. Therefore, as is apparent from Tables 1 and 2, in the clamp sensors (for example, the sensor 3 and the sensor 5) having different shunt resistance values, the difference in the shunt resistance value appears as the difference in the resistance value between the output terminals. Accordingly, the output voltage at the time of constant current supply is also significantly different. Therefore, discrimination between these clamp sensors (discrimination between types of voltage output type clamp sensors due to differences in shunt resistance values, that is, discrimination between the sensor 3 and the sensor 5) Is possible.

On the other hand, in the clamp sensors having the same shunt resistance value (for example, the sensor 3 and the sensor 6), the difference in the resistance value between the output terminals is only the difference in the winding resistance value. It is not always easy to discriminate.
In such a case, it is possible to determine the type of the clamp sensor by using output voltage information according to the temperature of the clamp sensor incidentally.

Here, FIG. 3 is a temperature-output voltage characteristic diagram of all the clamp sensors shown in Tables 1 and 2, and FIG. 4 shows three of the voltage output type clamp sensors in FIG. , 6) is enlarged.
According to FIG. 4, in the same temperature environment, the output voltage when supplying a constant current has a relationship of sensor 4 <sensor 3 <sensor 6. For example, the output voltage of sensor 6 at −10 ° C. in FIG. As the output voltage of the sensor 3 in FIG. 3 may be reversed, the type cannot be determined only by the output voltage. Therefore, a temperature sensor is provided on the measuring instrument side, and output voltages at a plurality of temperatures are measured and stored in advance. In addition, the determination may be made based on the value or the magnitude relationship.

  In the above embodiment, the first changeover switch 102 is connected to the voltage output type terminal a to supply a constant current to the clamp sensor, and the output voltage at that time is measured to determine the output type. However, even when the first changeover switch 102 is connected to the terminal b for current output type and a constant current is supplied to the clamp sensor, the combined resistance of the clamp sensor and the measuring instrument side shunt resistor 103 according to the output type. Since the values are different, it is possible to determine the output type of the clamp sensor from the sensor output voltage (output type confirmation signal 125).

  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 recognition key may be operated by the user and then step S1 and subsequent steps in FIG. 2 may be executed.

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 temperature-output voltage characteristic view according to the output type of a clamp sensor. It is the characteristic view which expanded and showed a part of FIG. 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: Protection diode 100: Measuring instrument 101: Clamp sensor connection terminal 102: First changeover switch 103: Measuring instrument side shunt resistance (resistance value R)
104: second changeover switch 105: constant current circuit 106: third changeover switch 107: amplifier circuit 108: detection circuit 109: A / D converter 110: CPU
111: Sensor detection button 112: Fourth changeover switch 113: Display 114: Output circuit 121-124: Switching signal 125: Output type confirmation signal

Claims (5)

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,
With a clamp sensor connected between a pair of input terminals of the measuring instrument, a constant current is supplied from the measuring instrument to the clamp sensor, and the input voltage of the measuring instrument at that time is measured to determine the output type of the clamp sensor. A method for discriminating the output type of a clamp sensor. In the clamp sensor output type discrimination method according to claim 1,
A measuring instrument side shunt resistor that can be connected between the input terminals is provided in the measuring instrument, and the measuring instrument side shunt resistance is connected between the input terminal and the first connection state in which the output signal of the clamp sensor is directly input. Provided with a selector switch for switching between the second connection state to be input,
A clamp sensor output type discriminating method, characterized in that a constant current is supplied from the measuring instrument to the clamp sensor via the changeover switch switched to the first connection state. In the clamp sensor output type discrimination method according to claim 1 or 2,
A plurality of types of voltage output type clamp sensors having different resistance values of the sensor-side shunt resistor are determined from the input voltage of the measuring instrument when a constant current is supplied to the clamp sensor, respectively. How to determine. 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
Means for supplying a constant current to the clamp sensor with the clamp sensor connected between the pair of input terminals;
Means for measuring an input voltage of the measuring instrument in a state where the constant current is supplied;
Means for discriminating the output type of the clamp sensor from the measured input voltage;
An output type discrimination device for a clamp sensor, comprising: In the clamp sensor output type discrimination device according to claim 4,
An output type discrimination device for a clamp sensor, wherein a plurality of types of voltage output type clamp sensors having different resistance values of the sensor side shunt resistor are discriminated from the measured input voltage.

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