JPH0448537Y2 - - Google Patents

Description

[Detailed explanation of the device] (a) Industrial application field This device applies a voltage between two points on the sample to be measured, and calculates the resistance value of the sample based on the voltage drop between the two points on the sample. This is a four-terminal resistance measuring device based on the voltage drop method that measures electrical contact resistance, and low resistance (resistance in the order of several milliohms or microohms) of fuses, conductors, semiconductors, etc. This invention relates to an AC four-terminal low resistance measuring device for highly accurate measurement in accordance with practical conditions.

(b) Prior art As is well known, when measuring resistance based on the voltage drop method on contact parts of electronic circuits where circuits are constructed using weak currents and voltages, large amounts of power (voltage x current) are required. When applied with
This has the problem that electrical film breakdown occurs and the measured resistance value is different from the resistance value in practical use. To solve this problem, resistance value measurement under a low power system (micro current, micro voltage) is required. On the other hand, when measuring the low resistance mentioned above, it is necessary to prevent the specific resistance of the measurement cable (generally, the resistance of a cable of about 1 m is several tens of milliohms), terminal clips, etc. from interfering with the measured value. This causes a measurement error in the resistance value of the object to be measured. A four-terminal voltage drop measurement method has been adopted as a general means to solve this problem.

A conventional low resistance measuring device that takes these points into consideration is known as a method that applies a constant current sine wave to the sample to be measured via transformer coupling (AC coupling). With this method, it is extremely difficult to set the peak value of the sine wave to an accurate value.
And because it includes a transformer coupling in the closed loop, the transformer coupling will occur at the moment when a constant current pulse is applied to the sample resistance (such as when a measurement clip is connected, a switch is turned on and off, or when a contact is chattering). Due to the feedback delay caused by this, a load higher than the specified constant current or open circuit voltage may be instantaneously applied to the sample resistor, resulting in damage to the film on the contact surface, etc., resulting in low resistance or This caused trouble in measuring electrical contact resistance.

(c) Purpose of the invention Therefore, the purpose of this invention is to reduce the contact resistance of electrical contacts or the electrical resistance of joints in electronic circuits under practical conditions by using a low-power system that uses minute currents and voltages. Another object of the present invention is to provide an AC four-terminal type low resistance measuring device that can perform measurements with extremely high accuracy.

(d) Structure of the device In order to achieve the above-mentioned purpose, this device specifically uses a constant current that is directly coupled to the sample to apply a voltage between two points on the sample to be measured. It consists of a drive section and a voltage measurement section that measures the resistance value of the sample based on the voltage drop value of the voltage applied to the sample, and the constant current drive section generates a triangular wave or a sine wave with a preset reference. A constant voltage generation circuit that generates a constant voltage trapezoidal wave by limiting according to a signal, a voltage-current conversion circuit that converts the output voltage of the constant voltage generation circuit into a constant current according to a preset range, and the conversion circuit. and an applied voltage limiting circuit that opens the output side of the constant voltage generation circuit when the output from the constant current drive unit to the sample exceeds a preset applied voltage value, an amplifier circuit that detects a voltage drop value between the samples when applied; a time-division synchronous detection circuit that removes noise and drift elements occurring in the output of the amplifier circuit, converts AC to DC, and outputs the converted output; This is an AC four-terminal low resistance measuring device comprising a measured value display means for displaying a signal.

(e) Description of Embodiments Hereinafter, the AC four-terminal low resistance measuring device according to this invention will be described in detail based on specific embodiments shown in the drawings. The AC four-terminal low resistance measuring device 1 of this invention basically consists of a constant current drive section A and a voltage measurement section B. A specific embodiment of the constant current drive unit A will be described with reference to FIG. The constant current driving section A has a trapezoidal wave constant voltage generating circuit 2 which is constituted by a triangular wave (or sine wave) generating circuit 3, a reference signal generating circuit 4, and a limiter circuit 5. The triangular wave generating circuit 3 has a frequency f, for example.
It is connected to supply the limiter circuit 5 with a triangular wave _e1 of ≒200Hz and a peak value of ±3V. On the other hand, the reference signal generating circuit 4 supplies a reference voltage e ₂ of, for example, ±1 V to the limiter circuit 5 using a highly accurate Zener diode. The limiter circuit 5 inputs the triangular wave signal e ₁ of the triangular wave generating circuit 3 and the reference signal e ₂ of the reference signal generating circuit 4, and generates the triangular wave signal e _{1 .}
is limited to a trapezoidal wave signal _e3 and output. The constant current drive unit A includes a timing signal generation circuit 6 connected to the triangular wave generation circuit 3 and the limiter circuit 5, and outputs a timing signal to a time division synchronous detection circuit in the voltage measurement unit B, which will be described later. connected to. The trapezoidal wave signal
In the measurement current switching circuit 7, e ₃ is set to 1/10, that is, ±
Switched to 0.1V trapezoidal signal _e4 . The trapezoidal wave signal e ₄ is converted into an input constant current waveform i ₁ in the voltage-current conversion circuit 8 and then sent to the constant current measurement cable 9,
Electricity is applied to the sample S via 10. On the other hand, an applied voltage limiting circuit 11 is connected to the output side of the conversion circuit 8 in order to immediately interrupt the current flowing through the sample S when the voltage applied to the sample exceeds a preset voltage value, for example, ±20 mV. ing. On the other hand, the output of the applied voltage limiting circuit 11 is connected to a cut-off circuit 12 provided between the measuring current switching circuit 7 and the voltage-current converting circuit 8, so that the voltage applied to the sample S exceeds the limit value. In this case, the circuit between the measurement current switching circuit 7 and the voltage-current conversion circuit 8 is opened to reliably cut off the current supply to the sample S. According to the constant current drive section A configured as described above, a constant current pulse converted based on a constant voltage trapezoidal wave can be directly coupled to the sample S as a specified constant current. On the other hand, when the clips are open, or when a high resistance greater than the range is connected between the clips, the voltage across the current clips increases linearly from OV as seen in the rising slope of the trapezoid. do. In this case, if the specified open-circuit voltage (V ₀ :voltage between terminals when there is no sample...for example, ±20mV) is exceeded, the applied voltage limiting circuit is activated and the current to the sample can be immediately cut off. . That is, by applying this trapezoidal wave, it is possible to easily and reliably set the cutoff point in relation to the open circuit voltage limiting circuit.

On the other hand, since this device directly couples a constant current to the sample, noise components (especially electromagnetic noise components) from the measurement cable etc. are synchronized with the waveform of the measured value (trapezoidal wave) and detected. It has the disadvantage of being measured. Therefore, in this invention, a circuit configuration for noise removal is provided in connection with the voltage measuring section B. The voltage measuring section B includes:
An amplifier circuit 15 is provided via measurement cables 13 and 14 connected to the sample S. The amplifier circuit 15 includes a first-stage differential amplifier 16 and a second-stage amplifier 17 including range switching.
For example, the output of
The ranges of ×10 and ×100 are set. The output signal _e5 of the amplifier circuit 15 includes cable noise and the like. Noise components for the trapezoidal wave occur in the rising and falling parts as shown in the figure. Therefore, for the purpose of removing this noise component, a time division synchronous detection circuit 18 is installed at the next stage of the amplifier circuit 15. The time division synchronous detection circuit 18
outputs a measured value signal e ₆ excluding cable noise and drift. The time division synchronous detection circuit 1
8 simultaneously converts an AC signal into a DC signal and outputs it. The time-division synchronous detection circuit 18 is connected to the timing signal generation circuit 6 in the constant current drive section A, and operates synchronously. The output of the time-division synchronous detection circuit 18 is passed through a low-pass filter 19 to smooth the pulsating signal, convert it into a DC voltage, and supply it to the measured value display means 20. The measured value display means 20 consists of a display instrument 21 and a recorder 22.

(f) Effects of the invention The AC four-terminal low resistance measuring device of this invention with the above configuration is extremely effective in measuring low resistances of several milliohms or several microohms under practical conditions. It is something. In other words, in this invention, a constant voltage of a trapezoid wave obtained by limiting a triangular wave (or sine wave) with a constant voltage is used as the voltage source applied to the sample. can be determined accurately, and a mode of direct binding to the sample can be adopted. Furthermore, according to this invention, by applying the above-mentioned trapezoidal wave and providing an applied voltage limiting circuit configured to immediately cut off the voltage applied to the sample when it exceeds a preset value, it is possible to maintain a constant current. This is extremely advantageous in setting the pulse cut-off point. On the other hand, the low resistance measuring device of this invention has a time division synchronous detection circuit in the voltage measuring section, which effectively eliminates noise components that occur synchronously in the waveform of the measured value as a result of direct coupling. It can be said that it is extremely effective in stabilizing the measured value voltage and enabling highly accurate measurement.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a specific example of the AC four-terminal type low resistance measuring device according to the invention, and each of FIG. 2 is a waveform chart showing aspects of output waveforms. A... Constant current drive section, B... Voltage measurement section, 1...
... Low resistance measuring device, 2 ... Trapezoidal constant voltage generation circuit, 5 ... Limiter circuit, 7 ... Measurement current switching circuit, 8 ... Voltage-current conversion circuit, 11 ... Applied voltage limiting circuit, 15 ... ...Amplification circuit, 18...Time division synchronous detection circuit, 20...Measurement value display means, S...
sample.

Claims (1)

[Claims for Utility Model Registration] A constant current drive unit directly coupled to the sample to apply a voltage between two points on the sample to be measured;
and a voltage measurement section that measures the resistance value of the sample based on the voltage drop value of the voltage applied to the sample, and the constant current drive section limits a triangular wave or a sine wave using a preset reference signal. a constant voltage generation circuit that generates a constant voltage trapezoidal wave; a voltage-current conversion circuit that converts the output voltage of the constant voltage generation circuit into a constant current according to a preset range; an applied voltage limiting circuit that opens the output side of the constant voltage generating circuit when the output exceeds a preset applied voltage value; an amplifier circuit that detects a voltage drop value between samples, a time division synchronous detection circuit that removes noise and drift elements occurring in the output of the amplifier circuit, converts AC to DC and outputs it, and displays the converted output signal. An AC four-terminal low resistance measuring device, characterized in that it is equipped with a measured value display means.