JP6134226B2 - Four-terminal resistance measuring device - Google Patents

Description

  The present invention relates to a four-terminal resistance measuring device.

  A four-terminal resistance measurement device using a double integration type A / D converter is capable of high-accuracy measurement, although not at high speed (see, for example, Patent Document 1). This four-terminal resistance measuring device is based on a constant current source that supplies a constant current for measurement to a resistor to be measured, and a voltage across the terminals generated when the measurement current flows through the resistor to be measured. A resistance value measuring unit that measures the resistance value of the resistor to be measured.

Japanese Patent Laid-Open No. 11-101830

  The above-described four-terminal resistance measurement device has a differential amplifier in the resistance value measurement unit. For this reason, since the input impedance of the resistance value measurement unit is high, there is an advantage that the leakage of the measurement current is small. On the other hand, the above-described four-terminal resistance measuring device has more components than a single-ended detection method that does not use a differential amplifier.

  The present invention has been made under such a background, and an object of the present invention is to provide a four-terminal resistance measurement device that can adopt a single-ended detection method while maintaining high measurement accuracy. To do.

  The present invention occurs in a pair of current supply terminals for supplying a measurement current to the resistor to be measured, a constant current source including an operational amplifier, a measurement current detection resistor, and a first power source that generate the measurement current, and the resistor to be measured. In the four-terminal resistance measurement device having a pair of voltage detection terminals for detecting a voltage and a voltage detection unit for detecting a voltage generated in the resistor under measurement via the voltage detection terminal, the voltage detection unit includes a first voltage detection unit. And a pair of current supply terminals connected to one end of the resistor to be measured outside the device and connected to the output of the operational amplifier inside the device. A current supply terminal, and the other current supply terminal connected to one end of the measurement current detection resistor inside the apparatus and connected to the other end of the resistor to be measured outside the apparatus, and a pair of voltages The detection terminal is covered outside the device. One voltage detection terminal connected to one end of the constant resistor and connected to the ground relating to the second power source inside the device, and connected to the other end of the resistor to be measured outside the device and The other voltage detection terminal connected to the voltage detection circuit that constitutes the voltage detection unit internally, and the ground relating to the first power supply is connected to the other end of the measurement current detection resistor.

  According to the present invention, it is possible to employ a single-ended detection method while maintaining high measurement accuracy.

It is a whole lineblock diagram of the four terminal resistance measuring device concerning an embodiment of the invention. It is a block diagram of the constant current source and voltage detection part of FIG. It is a block diagram of the four-terminal resistance measuring apparatus of a comparative example. It is a block diagram of the constant current source and voltage detection part of the four-terminal resistance measuring apparatus which concerns on other embodiment.

  A four-terminal resistance measurement apparatus 1 according to an embodiment of the present invention will be described with reference to FIGS.

  The four-terminal resistance measuring device 1 measures the resistance value of the resistor 2 to be measured. As shown in FIG. 1, the constant current source 11, a pair of current supply terminals Hi-side current supply terminals 12 and A Lo-side current supply terminal 13, a pair of voltage detection terminals, a Hi-side voltage detection terminal 14 and a Lo-side voltage detection terminal 15, a voltage detection unit 16, an A / D conversion unit 17, a processing unit 18, and a display unit 19 are provided. I have.

  The constant current source 11 is a DC constant voltage output from an internal power supply to the resistor 2 to be measured connected between a Hi side current supply terminal 12 and a Lo side current supply terminal 13 which are a pair of current supply terminals. Measurement current (DC constant current) Im, which is a current value (known current value) determined by the voltage value of and the resistance value of the measurement current detection resistor, can be supplied. The detailed configuration of the constant current source 11 will be described later with reference to FIG.

  The Hi-side current supply terminal 12 is connected to one output terminal of the constant current source 11. The Lo-side current supply terminal 13 is connected to the other output terminal of the constant current source 11. The Hi side voltage detection terminal 14 is connected to one input terminal of the voltage detection unit 16, and the Lo side voltage detection terminal 15 is connected to the other input terminal of the voltage detection unit 16.

  The voltage detection unit 16 detects a voltage generated between the Hi-side voltage detection terminal 14 and the Lo-side voltage detection terminal 15 connected to a pair of input terminals having a high input impedance, and outputs a voltage signal indicating the waveform of this voltage. The data is output to the A / D converter 17. The A / D conversion unit 17 receives the voltage signal and samples it at a predetermined sampling period, thereby generating voltage data indicating the voltage (amplitude) of the voltage signal and outputting the voltage data to the processing unit 18.

  The processing unit 18 includes a CPU and an internal memory, and executes resistance value measurement processing of the resistor under test 2 based on voltage data supplied from the A / D conversion unit 17 and displays measurement results. Supplied to the unit 19.

  The display unit 19 is configured by a display device such as an LCD (Liquid Crystal Display) as an example, and displays the result of the resistance value measurement process.

  Next, the operation of the four-terminal resistance measuring device 1 will be described. First, the connection of the Hi-side current supply terminal 12 and the Hi-side voltage detection terminal 14 to one terminal of the measured resistor 2, and the measured resistor of the Lo-side current supply terminal 13 and the Lo-side voltage detection terminal 15 The connection to the other terminal in 2 is performed by the measurer.

  In the operating state of the four-terminal resistance measuring device 1, the Hi-side current supply terminal 12 and the Hi-side voltage detection terminal 14 are normally connected to one terminal of the resistor 2 to be measured, and the Lo-side current supply terminal 13 and the Lo-side are connected. When the voltage detection terminal 15 is normally connected to the other terminal of the resistor 2 to be measured, from one output terminal of the constant current source 11, the Hi-side current supply terminal 12, the resistor to be measured 2, and the Lo-side current The measurement current Im is supplied to a path that reaches the other output terminal via the supply terminal 13.

  The voltage detection unit 16 detects a voltage generated between the Hi-side voltage detection terminal 14 and the Lo-side voltage detection terminal 15 and outputs a voltage signal indicating the voltage waveform to the A / D conversion unit 17. Then, the A / D converter 17 receives the voltage signal and samples it at a predetermined sampling period to generate voltage data indicating the voltage (amplitude) of the voltage signal, and outputs it to the processor 18. To do.

  As described above, in the state where each component of the four-terminal resistance measurement device 1 starts its operation, the processing unit 18 determines the resistance to be measured based on the voltage data output from the A / D conversion unit 17. The voltage value of the voltage which is the voltage between both ends of the body 2 is calculated, and based on the voltage value of the calculated voltage and the current value (known) of the measured current Im output from the constant current source 11, the resistor to be measured The resistance value of 2 is measured and displayed on the display unit 19.

  Next, the internal configuration of the constant current source 11 and the voltage detection unit 16 of the four-terminal resistance measurement device 1 will be described with reference to FIG. As shown in FIG. 2, the constant current source 11 is operated by a power source 40, and an output to which a pair of Hi-side current supply terminal 12 and Lo-side current supply terminal 13 for supplying a measurement current to the resistor 2 to be measured is connected. It has terminals 20 and 21, an operational amplifier 22 that generates a measurement current, a measurement current detection resistor 23, and a reference voltage source 24. The voltage detector 16 includes input terminals 25 and 26 to which a pair of Hi side voltage detection terminals 14 and Lo side voltage detection terminals 15 for detecting a voltage generated in the resistor 2 to be measured are connected, and a Hi side voltage detection terminal. 14 and the Lo side voltage detection terminal 15, a voltage detection unit 16 that detects a voltage generated in the resistor 2 to be measured, an A / D conversion unit 17 (not shown), a processing unit 18 (not shown), and The display unit 19 (not shown) is included.

  FIG. 2 shows a voltage detection circuit 27 as a main configuration of the voltage detection unit 16. The voltage detection circuit 27 includes an operational amplifier 28 and voltage detection resistors 29 and 30. 2 has a power supply 41 that is electrically insulated from the power supply 40 of the constant current source 11.

  The constant current source 11 outputs an internal reference voltage source 24 to the measured resistor 2 connected between the Hi-side current supply terminal 12 and the Lo-side current supply terminal 13 which are a pair of current supply terminals. A measurement current (DC constant current) Im that is a current value (known current value) determined by the voltage value of the DC constant voltage and the resistance value of the measurement current detection resistor 23 can be supplied as an output of the operational amplifier 22.

  The operational amplifier 22 of the constant current source 11 is supplied with operating power from the power supply 40 via the power supply terminals 32 and 33. Operational power is supplied from the power supply 41 to the operational amplifier 28 of the voltage detection circuit 27 via the power supply terminals 34 and 35.

  In the four-terminal resistance measuring device 1 having such an internal configuration, the Hi-side current supply terminal 12 is connected to one end of the resistor under test 2 outside the device, and an operational amplifier is connected via the output terminal 20 of the constant current source 11. 22 outputs. In addition, the Lo-side current supply terminal 13 is connected to the other end of the resistor 2 to be measured outside the apparatus and is connected to one end of the measurement current detection resistor 23 through the output terminal 21 of the constant current source 11. Further, the Hi side voltage detection terminal 14 is connected to one end of the resistor 2 to be measured outside the apparatus and is connected to the ground GNDb associated with the power supply 41 via the input terminal 25 of the voltage detection unit 16. In addition, the Lo side voltage detection terminal 15 is connected to the other end of the resistor 2 to be measured outside the apparatus, and the input terminal (+ side) of the operational amplifier 28 of the voltage detection circuit 27 via the input terminal 26 of the voltage detection unit 16. ). The ground GNDa related to the power source 40 of the constant current source 11 is connected to the other end of the measurement current detection resistor 23.

  In the four-terminal resistance measuring device 1 having the configuration described above, the measurement current flowing through the measured resistor 2 is detected by the measurement current detection resistor 23 of the constant current source 11. For this reason, if all of the current flowing through the measured resistor 2 does not flow through the measurement current detection resistor 23, a measurement error occurs. Therefore, in order to reduce the leakage current flowing from the Hi-side current supply terminal 12 and the Lo-side current supply terminal 13 to the ground GNDa without passing through the measurement current detection resistor 23, a well-known leakage current prevention measure is taken. As measures against leakage current, for example, a guard electrode that absorbs leakage current is installed, or a pattern adjacent to the output terminals 20 and 21 to which the Hi-side current supply terminal 12 and Lo-side current supply terminal 13 are connected is removed on the substrate. There are measures.

  At this time, if the ground GNDb is on the Lo-side voltage detection terminal 15 side as in the four-terminal resistance measuring device 50 of the comparative example shown in FIG. 3, it is necessary to prevent leakage current between the ground GNDb and the ground GNDa. Arise. That is, a part of the current flowing through the measured resistor 2 also flows to the ground GNDb side, so that the current flowing through the measured current detection resistor 23 and the current flowing through the measured resistor 2 are different, resulting in a measurement error. However, generally, the ground wiring needs to be widely routed on the substrate, and it is practically impossible to take measures such as removing the pattern adjacent to the guard electrode or the ground GNDb as described above. On the other hand, as shown in FIG. 2, the Hi-side voltage detection terminal 14 of the four-terminal resistance measuring device 1 is connected to the ground GNDb, and the Lo-side voltage detection terminal 15 is connected to the voltage via the input terminal 26 of the voltage detection unit 16. Since it is connected to the input terminal (+ side) of the operational amplifier 28 of the detection circuit 27 and the current flowing through the resistor 2 to be measured does not leak to the ground GNDb, it is not necessary to take measures against leakage current between the ground GNDb and the ground GNDa. This allows single-ended resistance measurement while maintaining high measurement accuracy.

  The four-terminal resistance measuring device 1 includes an operational amplifier 22 to a Hi-side current supply terminal 12 to a measured resistor 2 to a Lo-side current supply terminal 13 to a measurement current detection resistor 23 to a ground GNDa. In addition, since the Hi-side voltage detection terminal 14 is connected to the ground GNDb which is in an insulating relationship with the ground GNDa, the above-described operational amplifier 22 to the measured resistor 2 to the ground even when connected to the measured resistor 2. It does not affect the current flow of GNDa. Therefore, the current flowing through the resistor under test 2 can be easily controlled by the operational amplifier 22.

  In particular, in response to the user's desire to measure the resistance while leaving the oxide film of the relay contact using a weak current below a specified value as in the resistance measurement in a dry circuit, the four-terminal resistance measurement device 1 is A weak current below a specified value can be easily supplied to the resistor 2 to be measured.

  As described above, according to the four-terminal resistance measuring apparatus 1, it is possible to employ a single-ended detection method while keeping high measurement accuracy. Furthermore, current control can be easily performed for resistance measurement using a weak current, such as resistance measurement in a dry circuit.

(Other embodiments)
The embodiment of the present invention can be variously modified without departing from the gist thereof. A four-terminal resistance measuring device 1a according to another embodiment will be described with reference to FIG. In the four-terminal resistance measuring device 1a, the Hi-side current supply terminal 12 is connected to one end of the measured resistor 2 outside the device and is connected to one end of the measured current detection resistor 23a inside the device. In addition, the Lo-side current supply terminal 13 is connected to the other end of the resistor under test 2 outside the apparatus and is connected to the output of the operational amplifier 22a inside the apparatus. Further, the Hi-side voltage detection terminal 14 is connected to one end of the resistor 2 to be measured outside the device and is connected to the voltage detection circuit 27a inside the device. In addition, the Lo side voltage detection terminal 15 is connected to the other end of the resistor 2 to be measured outside the apparatus, and is connected to the ground GNDb associated with the power source 41a inside the apparatus. The ground GNDa related to the power source 40a of the constant current source 11 is connected to the other end of the measurement current detection resistor 23a.

  According to the configuration shown in FIG. 4, the current flowing from the ground GNDa to the measured resistor 2 through the measured current detection resistor 23a is then divided into the operational amplifier 22a side and the ground GNDb side. Since the current flowing through the resistor 2 is always equal to the current flowing through the measurement current detection resistor 23a, no measurement error occurs.

  Thus, the four-terminal resistance measuring device 1a has a configuration in which the configuration of the four-terminal resistance measuring device 1 is inverted. However, in the four-terminal resistance measurement device 1a, the reference voltage source 24a is connected to the + side input terminal of the operational amplifier 22a, and the ground GNDa is connected to the − side input terminal via the measurement current detection resistor 23a.

  As a result, the operational amplifier 22 of the four-terminal resistance measuring device 1 controls the output voltage with reference to the potential of the ground GNDa when the power is turned on, but the operational amplifier 22a of the four-terminal resistance measuring device 1a has the reference voltage when the power is turned on. The output voltage is controlled with reference to the potential of the source 24a. That is, the operational amplifier 22 of the four-terminal resistance measuring device 1 gradually increases the output voltage when the power is turned on, but the operational amplifier 22a of the four-terminal resistance measuring device 1a may be in a high output voltage state when the power is turned on. is there. Therefore, it is preferable to use the four-terminal resistance measuring device 1 when measuring the resistance of the resistor 2 to be measured with a weak current of a specified value or less as in the resistance measurement in the dry circuit described above.

DESCRIPTION OF SYMBOLS 1 ... Four terminal resistance measuring apparatus, 2 ... Resistor to be measured, 11 ... Constant current source, 12 ... Hi side current supply terminal (one current supply terminal), 13 ... Lo side current supply terminal (the other current supply terminal) , 14... Hi side voltage detection terminal (one voltage detection terminal), 15... Lo side voltage detection terminal (the other voltage detection terminal), 16, 16a... Voltage detection unit, 22, 22a, 28. ... Measurement current detection resistor, 24, 24a ... Reference voltage source, 27,27a ... Voltage detection circuit, 40,40a ... Power supply (first power supply), 41,41a ... Power supply (second power supply), GNDa, GNDb …ground

Claims (1)

A pair of current supply terminals for supplying a measurement current to the resistor under measurement;
A constant current source including an operational amplifier for generating the measurement current, a measurement current detection resistor, and a first power source;
A pair of voltage detection terminals for detecting a voltage generated in the measured resistor;
A voltage detection unit for detecting a voltage generated in the measured resistor through the voltage detection terminal;
In a four-terminal resistance measuring device having
The voltage detection unit includes a second power source that is in an insulating relationship with the first power source,
The pair of current supply terminals is
One current supply terminal connected to one end of the resistor under test outside the device and connected to the output of the operational amplifier inside the device;
The other current supply terminal connected to the other end of the resistor under test outside the apparatus and connected to one end of the measurement current detection resistor inside the apparatus;
Have
The pair of voltage detection terminals is
One voltage detection terminal connected to one end of the resistor to be measured outside the device and connected to the ground of the second power source inside the device;
The other voltage detection terminal connected to the other end of the resistor to be measured outside the device and connected to the voltage detection circuit constituting the voltage detection unit inside the device,
Have
The ground according to the first power supply is connected to the other end of the measurement current detection resistor.
A four-terminal resistance measuring device.

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