JP2005069786A - Four-terminal resistance measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a breakage of wires even during a measurement without having to interrupt the measurement in a four-terminal resistance measuring apparatus. <P>SOLUTION: A first AC current I<SB>ac1</SB>for detecting the breakage of wires is passed through a Hi-side current path including both a Hi-side current supply terminal 101 and a Hi-side voltage detection terminal 201 from a first AC current source 230, and a generated voltage is monitored by a second comparator 233. A second AC current I<SB>ac2</SB>for detecting the breakage of wires is passed through a Lo-side current path including both a Lo-side current supply terminal 102 and a Lo-side voltage detection terminal 202 from a second AC current source 240, and a generated voltage is monitored by a third comparator 242. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a four-terminal resistance measuring device having a pair of current supply terminals and a voltage detection terminal connected to a resistor to be measured, and more specifically, the connection state of each terminal (presence of disconnection) during measurement. ) Can be detected.

  The four-terminal resistance measurement is described in various documents, and in principle it is not affected by the wiring resistance of the measurement lead wire and the contact resistance of the probe pin (current supply terminal, voltage detection terminal). Therefore, it is often used for low resistance measurement.

  However, in reality, the contact resistance of the probe pin may not be ignored. The contact resistance of the probe pin is generally 1 Ω or less, but may be 1 kΩ or more depending on wear or oxidation by spark discharge. Further, as a previous problem, the probe pin may not come into contact with the measured resistor during probing, or the probe pin may be detached from the measured resistor during measurement.

  In this specification, not only the state in which the probe pin is not in contact with the resistor to be measured as described above, but also a contact failure including a case where the contact resistance of the probe pin is high is called “disconnection”. A conventional example provided with means will be described with reference to FIG. This conventional example is in accordance with the invention disclosed in Patent Document 1 below.

  The four-terminal resistance measuring device according to this conventional example has, as a basic configuration, a constant current source 10 that causes a measurement current to flow through the Hi-side current supply terminal 11a and the Lo-side current supply terminal 11b to the resistor Rx to be measured, A measurement unit 20 is provided for detecting a voltage drop generated in the measured resistor Rx by the measurement current via the Hi side voltage detection terminal 21a and the Lo side voltage detection terminal 21b.

  The voltage detected by the Hi-side voltage detection terminal 21a and the Lo-side voltage detection terminal 21b is amplified by the differential operational amplifier 22 and then converted into a digital signal by the A / D converter 23 to serve as an arithmetic control means. It is given to the CPU 24. The CPU 24 calculates a resistance value of the measured resistor Rx from the measurement voltage and the measurement current.

  In order to detect disconnection, a switch S1 that selectively connects the Hi-side current supply terminal 11a and the Hi-side voltage detection terminal 21a to the constant current source 10, a Lo-side current supply terminal 11b, and a Lo-side voltage detection terminal 21b And a switch S2 for selectively switching and connecting to the constant current source 10, and an amplitude monitor 25 comprising a comparator for monitoring the amplitude of the constant current source 10.

  This disconnection detection method focuses on the fact that the amplitude of the constant current source 10 becomes infinite when one of the terminals is disconnected. As an example, first, the switches S1 and S2 are both supplied with Hi-side current. The terminal 11a and the Lo side current supply terminal 11b are switched to connect to the constant current source 10. If the contact is poor at this time, a signal with disconnection is output from the amplitude monitor 25 to the CPU 24.

  Next, the switches S1 and S2 are both switched to the Hi side voltage detection terminal 21a and the Lo side voltage detection terminal 21b side and connected to the constant current source 10. If the contact is poor at this time, a signal with disconnection is output from the amplitude monitor 25 to the CPU 24 as described above. As described above, according to the above-described conventional example, it is possible to inspect whether or not the current supply terminals 11a and 11b and the voltage detection terminals 21a and 21b are disconnected with a simple configuration.

However, the disconnection does not occur only at the time of probing, but may also occur during measurement due to some cause. In the conventional example, if a disconnection occurs during the measurement, it cannot be detected. Therefore, a disconnection inspection is performed before entering the measurement, and in order to increase reliability, the disconnection inspection is performed after the measurement, and there is a problem that the disconnection inspection takes time.
JP 2000-111153 A

  Accordingly, an object of the present invention is to enable disconnection detection even during measurement without interrupting measurement in a four-terminal resistance measurement device.

  In order to solve the above-described problems, the present invention provides a constant current source that supplies a DC measurement current to a resistor under measurement via Hi-side and Lo-side current supply terminals, and Hi-side and Lo-side voltage detection. In a four-terminal resistance measuring device comprising a measuring unit for measuring the voltage of the resistor under measurement via a terminal, first disconnection detecting means for detecting a connection state of each current supply terminal with respect to the resistor under measurement And second disconnection detecting means for detecting the connection state of the Hi-side voltage detection terminal with respect to the measured resistor, and third disconnection detection means for detecting the connection state of the Lo-side voltage detection terminal with respect to the measured resistor. And determining means for determining a connection state of each terminal to the measured resistor based on an output signal from each disconnection detecting means, wherein the first disconnection detecting means has a predetermined amplitude and a predetermined current. First standard A first comparator for comparing the pressure, and the second disconnection detecting means supplies a first alternating current to a Hi-side current path including the Hi-side current supply terminal and the Hi-side voltage detection terminal. An AC current source; and a second comparator that compares a voltage generated in the Hi-side current path by the first AC current with a predetermined second reference voltage, and the third disconnection detecting means includes the Lo-side current A second AC current source for supplying a second AC current to a Lo side current path including a supply terminal and the Lo side voltage detection terminal; a voltage generated in the Lo side current path by the second AC current; A third comparator for comparing the three reference voltages is provided.

  According to a preferred aspect of the present invention, the second disconnection detecting means detects a voltage generated in the Hi-side current path synchronously with the first AC current source and applies the first lock-in to the second comparator. An amplifier is included, and the third disconnection detecting means includes a second lock-in amplifier that detects a voltage generated in the Lo-side current path synchronously with the second AC current source and supplies the voltage to the third comparator. .

  In order to eliminate mutual interference between the second disconnection detecting means and the third disconnection detecting means, it is preferable that the first alternating current source and the second alternating current source are not at the same frequency. Further, in order to eliminate adverse effects on the measured values of the first AC current source and the second AC current source, the measurement unit includes a low-pass filter that cuts off the AC component due to the first AC current and the second AC current. It is preferable that

  In the present invention, the ground on the constant current source side including the Lo side current supply terminal is insulated from the ground on the measurement unit side including the Lo side voltage detection terminal, and the first AC current source is Embodiments that are floating power supplies are included. In this case, the floating first alternating current source includes an oscillator, a transformer having the oscillator on the primary side and a secondary side connected to the Hi side current path, and a current limiting resistor on the secondary side of the transformer. And a DC blocking capacitor are preferably included.

  In addition, when the potential difference between the ground on the constant current source side and the ground on the measurement unit side is large, it is necessary to insulate the signal from the first comparator to the determination means. Therefore, the constant current source and the first comparator are The power supply system including the power supply system is preferably separated from the power supply system including the first and second alternating current sources, the first and second lock-in amplifiers, and the second and third comparators.

  When the Hi-side current supply terminal and the Hi-side voltage detection terminal are not in contact and the Lo-side current supply terminal and the Lo-side voltage detection terminal are not in contact, only the capacitance is interposed between them. Therefore, since the electrostatic capacity cannot be detected by the synchronous detection of the lock-in amplifier, in order to prevent this, a dummy load is connected to each of the first AC current source and the second AC current source. A side current path and the Lo side current path are connected in parallel.

  It is ideal that the four terminals contact the resistor to be measured accurately at the same time during probing, but instead, for example, the Lo side current supply terminal and the Hi side voltage detection terminal are covered earlier than the other terminals. When the measuring resistor is contacted, the second alternating current flows into the measured resistor and may cause damage depending on the resistive element.

  In order to prevent this, current control means for turning on and off the alternating current flowing from the first alternating current source and the second alternating current source to the Hi side current path and the Lo side current path is provided, It is preferable that an alternating current is passed through the Hi-side current path and the Lo-side current path after the terminal has surely contacted the resistor to be measured.

  In addition, in order to cancel the thermoelectromotive force generated by the contact between each terminal and the resistor to be measured, the polarity of the measurement current supplied to the resistor to be measured is reversed, or the measurement current is temporarily turned off. In order to prevent erroneous detection due to noise generated at that time, when the polarity of the measurement current is reversed or when it is temporarily turned off, the determination means determines the output signal supplied from each comparator as a predetermined value. It is preferable to disable the time.

  According to the present invention, the first AC current is supplied from the first AC current source to the Hi-side current path including the Hi-side current supply terminal and the Hi-side voltage detection terminal, and the generated voltage is supplied to the first AC current source. 2 is monitored, and the second AC current is supplied from the second AC current source to the Lo-side current path including the Lo-side current supply terminal and the Lo-side voltage detection terminal. Is monitored by the third comparator, so that disconnection can be detected even during measurement.

  Next, some embodiments of the present invention will be described with reference to FIGS. 1 to 9, but the present invention is not limited thereto.

In the first embodiment shown in FIG. 1, this four-terminal resistance measuring device supplies, as its basic configuration, a DC measuring current I _dc to a measured resistor Rx via a pair of current supply terminals 101 and 102. And a measurement unit 200 that detects a voltage drop of the resistor Rx to be measured generated by the measurement current I _dc through a pair of voltage detection terminals 201 and 202.

In this case, one of the current supply terminal 101 and the voltage detection terminal 201 is both on the Hi side, R _C1 and R _C2 are their contact resistances, and the other current supply terminal 102 and the voltage detection terminal 202 are both on the Lo side, R _C3 and R _{C C4} indicates their contact resistance. The Lo side current supply terminal 102 is connected to the ground GND1 on the constant current source 100 side, and the Lo side voltage detection terminal 202 is connected to the ground GND2 on the measurement unit 200 side. In this example, the ground GND1 and the ground GND2 are insulated.

  The measurement unit 200 includes a measurement system and a disconnection detection system, and the measurement system includes an amplifier 210, a low-pass filter 211, an A / D converter 212, and a control means 213 including, for example, a CPU having a determination function. In this example, a display (display means) 214 and an external device connection interface 215 are connected to the control means 213.

The disconnection detection system includes first to third disconnection detection means. The first disconnection detecting means compares the amplitude (DC amplitude; (R _C1 + Rx + R _C3 ) × I _dc ) of the constant current source 100 with a predetermined reference voltage V _ref1, and (R _C1 + Rx + R _C3 ) × I _dc > (or When ≧) V _ref1 , the first comparator 220 that sends a disconnection detection signal to the control means 213 is used.

The second disconnection detecting means includes a first AC current source 230 that supplies an AC current _Iac1 for detecting disconnection to a Hi-side current path including the Hi-side current supply terminal 101 and the Hi-side voltage detection terminal 201, and an AC current thereof. A differential amplifier 231 that detects and amplifies the AC voltage (R _C1 + R _C2 ) × I _ac1 generated in the Hi-side current path by I _ac1 , and receives a synchronization signal from the AC current source 230. The first lock-in amplifier 232 that performs synchronous detection and the output voltage V _RC1 that is synchronously detected by the first lock-in amplifier 232 are compared with a predetermined reference value V _ref2, and V _RC1 > (or ≧) V _ref2 And a second comparator 233 for sending a disconnection detection signal to the control means 213.

The third disconnection detecting means includes a second AC current source 240 that supplies an AC current _Iac2 for detecting disconnection to the Lo-side current path including the Lo-side current supply terminal 102 and the Lo-side voltage detection terminal 202, and the AC current. A second lock-in amplifier 241 that detects an AC voltage generated on the ground GND 1 side with respect to the ground GND ₂ by I _ac 2 using a synchronization signal from the second AC current source 240, and the second lock-in amplifier 241 performs synchronous detection. A third comparator 242 that compares the output voltage V _RC2 with a predetermined reference value V _ref3 and sends a disconnection detection signal to the control means 213 when V _RC2 > (or ≧) V _ref3 is provided.

As for the measurement operation, the measurement current I _dc is supplied from the constant current source 100 to the measured resistor Rx via the current supply terminals 101 and 102, and the voltage drop generated in the measured resistor Rx at that time is detected as the voltage detection terminal 201, The signal is detected at 202 and amplified to a predetermined level by an amplifier 210. Since this detection voltage includes an AC component due to the AC current I _ac1 for detecting the disconnection, the AC component is removed by the low-pass filter 211 and input to the A / D converter 212 to be converted into a digital signal. To the control means 213. The control means 213 calculates the resistance value of the measured resistor Rx from the detected voltage and the measured current, and displays it on the display 214, for example.

In this example, the AC component due to the AC current _Iac1 included in the detected voltage is removed by the low-pass filter 211, but an integral A / D converter may be used. In that case, if the period of the alternating current I _ac1 is close to the resistance measurement cycle may be set integration period to an integer multiple of the cycle of the AC current I _ac1. As another example, the AC component caused by the AC current _Iac1 can be canceled out by a sampling A / D converter or a ΔΣ A / D converter.

  Next, disconnection detection will be described. If one or both of the current supply terminals 101 and 102 are disconnected, the amplitude of the constant current source 100 becomes infinite, and thus is detected by the first comparator 220 that monitors the amplitude of the constant current source 100 as in the conventional example. The The control means 213 receives the disconnection detection signal from the first comparator 220 and displays, for example, “source terminal (current supply terminal) disconnection” on the display.

The disconnection detection of the Hi-side voltage detection terminal 201 will be described. When the contact resistances R _C3 and R _{C4 of} the Lo-side current supply terminal 102 and the Lo-side voltage detection terminal 202 are sufficiently small, the differential amplifier 231 includes (R AC voltage of _C1 + R _C2 ) × I _ac1 is input, but when high resistance measurement and Hi side contact resistances R _C1 and R _C2 are extremely large, power supply noise (50 Hz, 60 Hz) is superimposed on this AC voltage. The To eliminate the influence of the power supply noise, taking out only the voltage component due to the AC current I _ac1 through the first lock-in amplifier 232 in synchronization with the alternating current I _ac1.

On the other hand, if the CMRR (common-mode rejection ratio) of the differential amplifier 231 is insufficient, if the Lo side contact resistances R _C3 and R _C4 are large, the Lo side AC current I _ac2 The signal may be superimposed. To eliminate this effect, it is sufficient different from the frequency of the AC current I _ac2 of the alternating current I _ac1. When receiving the disconnection detection signal from only the second comparator 233, the control unit 213 displays, for example, “sense High terminal (Hi side voltage detection terminal) disconnection” on the display.

Then, with the described detection of a break in Lo-side voltage detection terminal 202, to ground GND1 of the constant current source 100 side measuring portion 200 side of the ground _GND2, the _{(R C3 + R C4) ×} I ac2 becomes voltage. When the Lo-side contact resistances R _C3 and R _C4 are extremely large, power supply noise (50 Hz, 60 Hz) is superimposed on the AC voltage as described above.

To eliminate the influence of the power supply noise, taking out only the voltage component due to the AC current I _ac2 through a second lock-in amplifier 241 in synchronization with the alternating current I _ac2. When the influence of external noise is small, a rectifier circuit can be used instead of the second lock-in amplifier 241. When receiving the disconnection detection signal only from the third comparator 242, the control means 213 displays, for example, “sense Low terminal (Lo side voltage detection terminal) disconnection” on the display.

  Note that when the potential difference between the ground GND1 on the constant current source 100 side and the ground GND2 on the measurement unit 200 side is large, it is necessary to insulate the signal from the first comparator 220 to the control means 213. Therefore, as shown in FIG. It is preferable that the current source 100 side and the measurement unit 200 side be separate systems.

That is, on the constant current source 100 side and the measurement unit 200 side, transformers 100a and 200a that individually step down the commercial power supply voltage to a predetermined level, diode bridges 100b and 200b that rectify the AC voltage in full wave, and a rectifying and smoothing circuit 100c It comprises 200c, thereby obtaining a first device in the power supply _{V cc1} of the constant current source 100 side, of the measuring unit 200 and a second device in the power supply _{V cc2.}

  In the first embodiment of FIG. 1, the first AC power supply 230 of the second disconnection detecting means is a floating power supply. As an example, a configuration comprising an oscillator OSC and a transformer T can be adopted as shown in FIG. .

That is, the oscillator OSC is connected to the primary side of the transformer T, and the secondary side thereof is connected to the Hi side current path (current path including the Hi side current supply terminal 101 and the Hi side voltage detection terminal 201). On the next side, a current limiting resistor R1 and a capacitor C1 are connected in series. The capacitor C1 is a DC blocking capacitor that prevents the measurement current I _dc from flowing into the Hi-side voltage detection terminal 201. By making the current limiting resistance R1 larger than the Hi-side contact resistances R _C1 and R _C2 , a substantially constant current source can be obtained.

  As a modification of the floating power supply, the current limiting resistor R1 may be moved from the secondary side of the transformer T between the primary side of the transformer T and the oscillator OSC as shown in FIG. The differential amplifier 231 can be made unnecessary by directly inputting the voltage on the side to the first lock-in amplifier 232.

Next, a second embodiment of FIG. 5 will be described. If, for example, the Hi-side current supply terminal 101 and the Hi-side voltage detection terminal 201 are completely open during probing, only the capacitance C _c1 exists between them, so that the differential amplifier 231 is connected to the differential amplifier 231. The input signal has a phase rotated by 90 °, and the capacitance C _c1 is not detected by the first lock-in amplifier 232.

This is the same even when the Lo-side current supply terminal 102 and the Lo-side voltage detection terminal 202 are completely open, and the capacitance C _c2 between them is not detected by the second lock-in amplifier 241. .

  Therefore, in the second embodiment, dummy loads 230a and 240a including resistors and capacitors, for example, are connected to the first AC current source 230 and the second AC current source 240, respectively, and the Hi side current path and the Lo side current path. Are connected in parallel.

Next, a third embodiment of FIG. 6 will be described. This third embodiment is for the case where the constant current source 100 side and the measuring unit 200 side power supply are not insulated. In this case, the disconnection detecting AC current from the second AC power supply 240 of the third disconnection detecting means is used. I _ac2 can _flow from the Lo-side voltage detection terminal 202 side toward the ground GND1 of the constant current source 100. The first disconnection detection unit and the second disconnection detection unit may be the same as those in the first embodiment, but a differential amplifier 210a is used instead of the amplifier 210 in the measurement system.

  As a modification of the third embodiment, an inverting operational amplifier 240b is connected in parallel with the Lo side current path between the second AC power supply 240 and the ground GND1 as shown in FIG. Compared to the example, it is possible to select a differential amplifier 210a having a low CMRR.

Next, a fourth embodiment of FIG. 8 will be described. It is ideal that the two terminals 101 and 102 on the Hi side and the two terminals 201 and 202 on the Lo side are in contact with the measured resistor Rx at the same time during probing. As shown in FIG. 2, when the Lo-side current supply terminal 102 and the Hi-side voltage detection terminal 201 contact the measured resistor earlier than the other terminals 101 and 202, the second AC current I _ac2 for detecting disconnection Flows into the measured resistor Rx and may be damaged depending on the resistance element (for example, MR element or chip inductor).

To prevent this, in the fourth embodiment, the first AC power source 230 and the second AC power supply 240, let a switch SW1, SW2 for turning on and off the AC current _{I ac1, I ac2} for detecting disconnection, non The switches SW1 and SW2 are turned off at the time of measurement, and the switches SW1 and SW2 are turned on at the time when the probing of the four terminals is finished at the time of measurement.

  The switches SW1 and SW2 may be either mechanical or electronic, but as another method, for example, the amplitude of an oscillator included in the AC power supply may be controlled on and off. In FIG. 8, R2 and C2 are filters provided in the input stage of the amplifier 210.

Further, in the four-terminal resistance measurement, the measurement current I _dc supplied to the measured resistor Rx is canceled in order to cancel the thermoelectromotive force generated by the contact between each terminal 101, 102, 201, 202 and the measured resistor Rx. In general, current control is performed such that the polarity of the current is reversed or the measurement current I _dc is temporarily turned off. At this time, whisker-like noise as shown in FIG. 9 is generated. This noise often exceeds the reference voltages V _ref1 , V _ref2 , V _ref3 of each of the disconnection detecting means.

In order to prevent erroneous detection due to noise generated during current control, the control means 213 assumes that a disconnection detection signal is output from each of the comparators 230, 233, and 242 when the polarity of the measurement current I _dc is reversed or temporarily turned off. However, it is preferable to disable it for a predetermined time.

  As described above, according to the present invention, the disconnection can be detected even during the measurement without interrupting the measurement in the four-terminal resistance measurement device, so that the measurement time can be shortened and the reliability of the measurement accuracy can be improved.

1 is a circuit diagram showing a first embodiment of a four-terminal resistance measurement device according to the present invention. The circuit diagram which shows the structure of the power supply of the said 1st Embodiment. The schematic diagram which shows an example of the alternating current power supply used in the said 1st Embodiment. The schematic diagram which shows the modification of the said AC power supply. The circuit diagram which shows 2nd Embodiment of the four-terminal resistance measuring apparatus by this invention. The circuit diagram which shows 3rd Embodiment of the four-terminal resistance measuring apparatus by this invention. The circuit diagram which shows the modification of the said 3rd Embodiment. The circuit diagram which shows the principal part of 3rd Embodiment of this invention. The wave form diagram which shows the noise which generate | occur | produces at the time of current control of measurement current. The circuit diagram which shows the four-terminal resistance measuring apparatus of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Constant current source 101 Hi side current supply terminal 102 Lo side current supply terminal 200 Measuring part 201 Hi side voltage detection terminal 202 Lo side voltage detection terminal 210 Amplifier 211 Low pass filter 212 A / D converter 213 Control means 220 1st comparator 230 1st 1 AC power supply 231 differential amplifier 232 first lock-in amplifier 233 second comparator 240 first AC power supply 241 second lock-in amplifier 242 third comparator

Claims (10)

A constant current source for supplying a DC measurement current to the resistor under measurement via the Hi side and Lo side current supply terminals, and the voltage of the resistor under measurement via the Hi side and Lo side voltage detection terminals. In a four-terminal resistance measuring device comprising a measuring unit for measuring
A first disconnection detecting means for detecting a connection state of each of the current supply terminals to the resistor to be measured; a second disconnection detecting means for detecting a connection state of the Hi-side voltage detection terminal to the resistor to be measured; Third disconnection detecting means for detecting a connection state of the Lo-side voltage detection terminal with respect to the resistor to be measured, and determining a connection state of each terminal with respect to the resistor to be measured based on an output signal from each of the disconnection detection means. Determination means for
The first disconnection detecting means has a first comparator for comparing the amplitude of the constant current source with a predetermined first reference voltage,
The second disconnection detecting means includes a first AC current source for supplying a first AC current to a Hi side current path including the Hi side current supply terminal and the Hi side voltage detection terminal, and the first AC current. A second comparator for comparing a voltage generated in the Hi-side current path with a predetermined second reference voltage;
The third disconnection detecting means includes a second AC current source for supplying a second AC current to a Lo side current path including the Lo side current supply terminal and the Lo side voltage detection terminal, and the second AC current. A four-terminal resistance measuring device, comprising: a third comparator that compares a voltage generated in the Lo-side current path with a predetermined third reference voltage.   The second disconnection detecting means includes a first lock-in amplifier that detects a voltage generated in the Hi-side current path synchronously with the first AC current source and supplies the voltage to the second comparator, and the third disconnection detector The detection means includes a second lock-in amplifier that detects a voltage generated in the Lo-side current path synchronously with the second AC current source and supplies the voltage to the third comparator. 4. The four-terminal resistance measuring device according to 1.   The four-terminal resistance measuring device according to claim 1 or 2, wherein the first alternating current source and the second alternating current source are not at the same frequency.   The four-terminal resistance measuring device according to claim 1, 2 or 3, wherein the measurement unit includes a low-pass filter that cuts an AC component due to the first AC current and the second AC current.   The constant current source side ground including the Lo side current supply terminal and the measurement unit side ground including the Lo side voltage detection terminal are insulated, and the first AC current source is a floating power source. The four-terminal resistance measuring device according to any one of claims 1 to 4, wherein   The floating first alternating current source includes an oscillator, a transformer having the oscillator on the primary side and a secondary side connected to the Hi side current path, and a current limiting resistor and a DC block on the secondary side of the transformer The four-terminal resistance measuring device according to claim 5, further comprising a capacitor for use.   A power supply system including the constant current source and the first comparator is separated from a power supply system including the first and second AC current sources, the first and second lock-in amplifiers, and the second and third comparators. The four-terminal resistance measuring device according to claim 5 or 6, wherein   2. A dummy load is connected to each of the first AC current source and the second AC current source so as to be parallel to the Hi-side current path and the Lo-side current path, respectively. The four-terminal resistance measuring device according to any one of Items 7 to 7.   2. A current control means for turning on and off an alternating current flowing from the first alternating current source and the second alternating current source to the Hi side current path and the Lo side current path. The four-terminal resistance measuring device according to claim 1.   When the polarity of the measurement current supplied to the resistor to be measured is reversed, or when the measurement current is temporarily turned off, the determination means outputs the output signal supplied from each comparator for a predetermined time. The four-terminal resistance measuring device according to any one of claims 1 to 8, which is invalidated.

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