JPH045576A - Contact resistance testing device - Google Patents

Abstract

PURPOSE:To prevent a wrong test and to conduct a contact test with high reliability by providing a comparing circuit, a resistance, etc., and deciding whether or not the contacting of probes is normal or not when a constant current is supplied to a material to be tested through probes to detect a voltage drop due to a contact resistance through the probes. CONSTITUTION:The constant current is supplied from a constant current generator 2 to the material 1 to be tested such as a switch through the probes P1 and P2 and the detected voltage drop due to the contact resistance through probes P3 and P4 is processed by a differential amplifier 3 and an A/D converter 4, and displayed on a display unit 5, thereby testing whether or not the resistance value of the sample 1 is normal or not. The resistance R1 is connected in parallel to the probes P1 and P3 and the value of the voltage drop through the resistance R1 is compared by a comparing circuit 8 with a decision level value which is almost a half as large as the saturation voltage of the generator 2 to decide whether the probes P1 and P3 contact each other normally or not; and resistance value normalcy misdecision making due to a defect in contacting between the probes is prevented and no defective is mixed in normal articles, so that the contact resistance test with high reliability can be conducted. Further, it is decided through a parallel resistance R2 similarly whether the probes P2 and P4 contact each other normally or not.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a testing device for mechanical switches such as reed switches and pushbutton switches, and particularly to a contact resistance testing device for preventing the mixing of defective products with non-defective products.

In devices that combine reed switches, pushbutton switches, etc. with semiconductor integrated circuits, the contact properties of the contacts in these mechanical switches often affect the performance of the device, and contact resistance is one of the many test items for mechanical switches. exams are given great importance. However, since the contact resistance value of the contacts is small, it is difficult to distinguish between non-defective products and defective products, and when testing with testing equipment with low reliability, defective products are often mixed in with the non-defective products. However, it is absolutely necessary to prevent defective products from mixing with good products. Therefore, it is desired to realize a contact resistance testing device with high reliability.

[Prior art] Fig. 3 is a block diagram showing a conventional first test device;
The figure is a block diagram showing a conventional second test device.

The conventional first test device is a test sample 1 as shown in Fig. 3.
a constant current generator 2 that supplies current to the terminals of the terminal via probes P1 and R2, a differential amplifier 3 that detects a voltage drop due to contact resistance via probes P3 and P, and an output of the differential amplifier 3. An analog/digital converter (A/D converter) 4 that digitizes voltage, a display 5 that displays the voltage or resistance value output from the A/D converter 4, and a display device 5 that displays the voltage or resistance value as a standard value. It is provided with a determination circuit 6 that compares and determines whether the contact resistance is good or bad.

Furthermore, as shown in FIG. 4, the conventional second test apparatus includes, in addition to the above circuit, a probe P1. It is equipped with a continuity check circuit 7 for detecting poor contact between relay contacts rl, r1 . , R13, rla
connected to probes P1, R2, R3, P4 via
If there is a contact failure in any one of the probes P, , P, , R3, and P4, the determination circuit 6 is configured to invalidate the determination of pass/fail.

[Problem to be solved by the invention] However, in the case of the conventional first test device, the probes P8, P
If the contact resistance of z exceeds a certain value, it becomes impossible to flow a constant current from the constant current generator to the test sample, and even if the contact resistance value of the test sample exceeds the specified value, the voltage will drop. It is judged to be a good product because it is small. Similarly probes P3, R
When the contact resistance of 4 approaches the input impedance of the differential amplifier 3, the voltage drop due to the sample under test is divided and a small voltage is input to the differential amplifier 3, and the contact resistance value of the sample under test exceeds the specified value. Even if it is, it is judged to be a good product. That is, there was a problem in that test samples that were supposed to be defective products were mixed into non-defective products.

In addition, the conventional second test device is capable of checking the contact resistance of the probe, and unlike the first test device, the test sample that should be a defective product does not mix in with a good product.
The problem is that checking the contact resistance of the probe and testing the contact resistance of the test sample are performed alternately, and it takes a long time to test the contact resistance of the test sample.

An object of the present invention is to provide a contact resistance testing device which prevents defective products from being mixed with non-defective products only by testing the contact resistance of a test sample, and which has a high degree of reliability.

[Means to solve the problem]

FIG. 1 is a block diagram showing a test device according to the present invention. The same objects are represented by the same symbols throughout the plan.

The above problem involves a constant current generator 2 that supplies current to the sample under test 1 via probes P, , P, and probes P3, R4.
A differential amplifier 3, an analog/digital converter 4, and a display device for detecting the voltage drop due to the contact resistance of the sample under test 1 via the 5 and a determination circuit 6, a comparison circuit 8 for preventing erroneous determination due to poor contact between probes P1 and R2, and resistors R1 and R2 for preventing erroneous determination due to poor contact between probes P3 and R4. This is achieved by the contact resistance testing device of the present invention, which prevents defective products from being mixed with non-defective products.

[For production]

In FIG. 1, there is a comparison circuit for preventing erroneous judgment due to poor contact between the probes P L and P t, and a probe P3.
, a resistor R to prevent misjudgment due to poor contact of R4.
By providing ,,R, there is no need to check the contact state of the probe each time the contact resistance value of the test sample is tested, and the mixing of defective products with non-defective products can be prevented by simply testing the contact resistance of the test sample. Moreover, it is possible to realize a highly reliable contact resistance testing device.

〔Example〕

Embodiments of the present invention will be described below with reference to the accompanying drawings. Note that FIG. 2 is a circuit diagram showing the operating principle of the test apparatus according to the present invention.

As shown in FIG. 1, the test device according to the present invention
a constant current generator 2 that supplies current to the terminals of the terminal via probes P3 and R2, a differential amplifier 3 that detects a voltage drop due to contact resistance via probes P3 and R4, and an output voltage of the differential amplifier 3. An A/D converter 4 that digitizes the
It includes a display 5 that displays the voltage or resistance value output from the /D converter 4, and a determination circuit 6 that compares the voltage or resistance value with a standard value to determine whether the contact resistance is good or bad.

The test apparatus according to the present invention also includes a comparison circuit 8 that prevents erroneous determination by utilizing the fact that the voltage of the constant current generator 2 increases when the contact resistance of the probes P1 and R2 is large.

The comparator circuit 8 has a comparator 81, a photocoupler 82, and a gate circuit 83 as shown in FIG.
1 is applied.

When testing contact resistance, the voltage of constant current generator 2 is the reference voltage V.
If it is larger than s, a signal indicating poor contact between the probes P1 and R2 is outputted via the gate circuit 83.

Furthermore, the test device according to the present invention includes probe P1. P.

Resistor R1 and probes Pz, P connected in parallel with.

and a resistor R2 connected in parallel with the probe P.
3. Prevents misjudgment due to poor contact of R4. Second
In the figure, current is supplied from the constant current generator 2 to the sample under test 1 via the contact resistances r, , rz of the probes, and if the contact resistances r, , R2 of the probes are low values below the allowable value, , the voltage between the terminals of the sample l under test becomes a value proportional to the resistance value of the sample l under test. However, if the contact resistance of one of the probes exceeds the allowable value, the constant current generator 2 will no longer be able to supply a constant current, and the voltage between the terminals of the test sample 1 will become lower than the above voltage.

Similarly, the sample under test l is connected to the differential amplifier 3 via the contact resistances r3 and R4 of the probe, and the voltage between the terminals of the sample under test 1 and the input voltage of the differential amplifier 3 are determined by the contact resistances r3 and R4 of the probe. are approximately equal if they are less than the allowable value. However, when the contact resistance of one of the probes becomes larger, the input voltage of the differential amplifier 3 becomes lower than the voltage between the terminals of the sample under test 1.

However, a resistor R1 is connected in parallel with the contact resistors r+ and r3, and a resistor R2 is connected in parallel with the contact resistors r2 and R4. Therefore, the voltage of the constant current generator 2 is divided by the contact resistances r3 and R4 and the resistances R1 and R2 and input to the differential amplifier 3.

That is, when the contact resistances r3 and R4 exceed the allowable values, a voltage higher than the voltage between the terminals of the sample under test 1 is applied to the differential amplifier 3, and the sample is determined to be defective regardless of whether the sample under test I is good or defective. Ru. The comparison circuit 8 includes a probe P1. Although it is possible to detect a contact failure of Pz, it is not possible to prevent erroneous determination due to contact failure of the probes P4 and R4. However, by connecting a resistor in parallel, poor contact between the probes P3, P can be detected. In addition, R+, Rz is 100Ω
If the contact resistance of the probe is below the allowable value, there will be no error in the detected voltage.

In this way, by providing a comparison circuit to prevent erroneous judgments due to poor contact between probes P3 and R2, and resistors R+ and Rz to prevent erroneous judgments due to poor contact between probes P3 and R4, the There is no need to check the contact status of the probe every time you test the contact resistance value.
It is possible to prevent defective products from being mixed with non-defective products only by testing the contact resistance of the sample under test, and to realize a highly reliable contact resistance testing device.

[Effects of the Invention] As described above, according to the present invention, it is possible to prevent the mixing of defective products with non-defective products only by performing a contact resistance test on a test sample, and to provide a highly reliable contact resistance testing device.

83 is a gate circuit, 82 is a photocoupler, R1 and R2 are resistances, P,,P,,R3,R4 are Brouf, rl, r, , r, , R4 is contact resistance, respectively.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a test device according to the present invention. FIG. 2 is a circuit diagram showing the operating principle of the test device according to the present invention. FIG. 3 is a block diagram showing a first conventional test device. FIG. 4 is a block diagram showing a second conventional test device. In the figure, 1 is a test sample, 2 is a constant current generator, 3 is a differential amplifier, 4 is an A/D converter, 5 is a display,
6 is a judgment circuit, 8 is a comparison circuit, 81 is a comparator, and a nail is placed in the '5 wipe 1 position in Kifu Akira ↑ 7゛ Old 11, 2
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Claims (1)

[Claims] A constant current generator (2) that supplies current to the test sample (1) via probes P_1 and P_2; probe P_3;
A differential amplifier (3) for detecting the voltage drop due to the contact resistance of the test sample (1) via P_4, displaying the contact resistance value, and determining the quality of the test sample (1).
and an analog/digital converter (4), a display (5), and a determination circuit (6), and a comparison circuit (8) for preventing erroneous determination due to poor contact between the probes P_1 and P_2, and a probe. P_3,
Resistor R to prevent misjudgment due to poor contact of P_4
_1, R_2, and is characterized in that it prevents defective products from mixing with non-defective products.