JPS5850471A - Continuity tester - Google Patents

Abstract

PURPOSE:To reduce a voltage and a current applied to a circuit to be tested and thereby to obtain a reliable continuity tester by a method wherein the resistance on one side of a bridge circuit is constituted by two resistors and both ends of one resistor of the two are used as input terminals. CONSTITUTION:This device is constituted by a bridge circuit 1 whose one side is composed of two resistors at least, by a differential amplifier 2, by a comparator 3 of the voltages of these elements, and by an indication means 4. Input terminals 12 and 13 whereby a continuity test is conducted are connected to the opposite ends of a resistor 11 of the bridge circuit 1, respectively. When the input terminals 12 and 13 are opened, the potential between the outputs 14 and 15 of the bridge circuit 1 is positive on the side of the output 14. When a resistance of 5OMEGA or below is connected between the input terminals 12 and 13, the potential of the outputs 14 and 15 turns negative on the side of the output 14, the outputs 16 and 17 of the differential amplifier 2 are inverted, the output of the voltage comparator 3 turns ON, and a buzzer 4 sounds.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for a measuring instrument that performs a continuity test on an electric circuit.

Checking the electrical wiring in an electrical circuit is the first step in testing equipment. Conventionally, a tester or a DC buzzer is used to test the continuity of electrical wiring. That is, a tester is used to read the resistance value between two points, and it is determined whether the wiring between them is correct. Alternatively, connect a buzzer with a battery connected between two points, and determine the wiring condition based on whether the buzzer sounds or not.

In the case of this conventional test equipment, the voltage applied between two terminals during measurement is the battery voltage, for example, about 1.5V.

On the other hand, among the electronic components used in devices, especially integrated circuits (IO), as the degree of integration increases, they are becoming more susceptible to electrical shrinkage, such as voltage and current. When we conducted a continuity test on 10 circuits using equipment, we found that circuit 0 was destroyed due to overvoltage, overcurrent, and current.
Or, even if it does not result in destruction, there is a defect in that it deteriorates the process and reduces the reliability of the device.

In particular, in the case of test equipment that consists only of a l'fJL battery and a buzzer, there is a defect in that the surge voltage caused by the inductance of the battery destroys the battery. There are some products that prevent overcurrent, but the defect is that the detection resistor, that is, the resistance that stops the buzzer from sounding, is very large at 50n- to IKfl, making it inaccurate for detecting subtle disconnections or continuity defects. be.

There is also a method that uses a tester to measure the resistance between two points to determine continuity, but with this method, you have to check the resistance each time, making it less workable. There is a flaw.

The present invention is a new invention that eliminates the above-mentioned defects, and its purpose is (1) to reduce the voltage applied to the circuit C, 1M, and the current, which is small.
To provide a continuity tester that does not deteriorate C.

(2) To provide a continuity tester that has a small detection resistance and can accurately judge the continuity state of a circuit.

(3) To provide a continuity tester with good workability.

consisting of a bridge circuit in which one of the four sides is made up of at least two resistors, a resistor connected in series to the precise circuit, a differential amplifier, a voltage comparator, and a display means,
This is achieved by using both ends of one of the two resistors on one side of the bridge circuit as input terminals.

Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

1 is an input circuit, 2 is a differential amplifier, 3 is a voltage comparator, 4 is a buzzer, 5 to 11 are resistors, 12.13 is an input terminal to be measured during a continuity test, 14.15 is a bridge circuit. output,
16.17 is the output of the differential amplifier.

18 and 19 are transistors forming a differential amplifier.

20 is a battery.

Input terminal 12 for two points for testing the continuity of the electrical circuit of the device.
．． 13, measure the resistance between them, and amplify the output 14.15 of the bridge circuit with differential amplifier 2.
Compare the outputs 16 and 17 with voltage comparator 3 and output buzzer 4.
to drive.

Input circuit 1 includes resistor 7. Resistance 8. Resistance 9 and 11° Resistance 10
It consists of a bridge circuit with four sides and a resistor 5.6, so '! ! This has the effect that there is little change in the detection resistance value due to changes in the voltage of the battery 20.

Input circuit 1 will be explained using an example of resistance value ○Resistance 7
．． 8.10 to 50 fl, resistance 9 to 45 rL, m resistance to 11
is 50OA. Input terminal i2. When x3 is open, the potential between outputs 14 and 15 of the bridge circuit is output 14.
There is positive pressure on the side. If a resistance of 5 (1 or less) is connected to the input terminals 12 and 13, the potential between the outputs 14 and 15 of the Presiji circuit will become negative on the output 14 side, and the differential amplifier 2 (
-A9 outputs 16 and 17 are reversed, the output of voltage comparator 3 is turned on, and buzzer 4 sounds. That is, when the resistance connected to the input terminals 12 and 13 begins to fall below the detection resistance value, the output 14.
By selecting the resistance values on each side of the pre-radiation circuit so that the positive and negative potentials between the two sides are reversed, a highly sensitive continuity tester with a small detection resistance value can be realized. The detection resistance value in this case is 5 (l).

By connecting the resistor 5.6 in series with the bridge circuit, the voltage of the battery 20 can be divided and the voltage across the resistor 110, that is, between the input terminals 12.13, can be reduced, so the voltage applied to the 0 circuit during the continuity test can be reduced. If the current is small, the current flowing through the circuit will also be limited. Resistance 5.6 is husband 4
Ω, 5Kn, when the battery voltage is 3V, input terminal 1
The voltage when 2.13 is open is 3OFFIV or less, and the current when short-circuited is 0-4mA or less, so there is no deterioration of the circuit.

Of course, due to the 9-circuit configuration, no surge voltage or surge current is applied.

Voltage comparator 3, which operates from a single power supply, has large errors and uncertain multi-operation when the comparison voltage is set to 0V or near the power supply voltage, but by dividing the series resistance and dividing it into resistors 5 and 6, voltage comparator 3 can be operated near the center of the voltage of the battery 20, making it possible to improve the accuracy of voltage comparison.

FIG. 2 is a circuit diagram of a second embodiment of the present invention.

22 is a zeroed operational amplifier, 23 is a variable resistor for zero point adjustment, 24 is the output of the operational amplifier 22, 25.
26 is a resistor for creating a reference voltage for voltage comparator 3, 27
is the voltage comparator 30 reference voltage input.

The variable resistor 23 is originally intended to adjust the zero point of the operational amplifier 22, but in this embodiment, the operation of the voltage comparator 3 is adjusted by moving the zero point of the output 24 and bringing the voltage comparison to the center of the power supply voltage. ensure that

If the variable resistor 23 is adjusted so that the output 24 of the operational amplifier 22 becomes smaller than the reference voltage input 27 when the resistance of the input terminal 12.13 exceeds the detection resistance value, the input terminal 12.
．． When the resistance 13 goes below the detection resistance, the output 24 becomes larger than the reference voltage input 27, so the output of the voltage comparator 3 turns on and the buzzer 4 sounds.

In the above description, a case has been described in which the continuity indicating means is a buzzer, but the present invention is not limited to this, and it goes without saying that the present invention can be similarly implemented with a display device such as a light emitting diode or a lamp.

As explained above, according to the present invention, one of the four sides is composed of a bridge circuit consisting of at least two resistors, a resistor connected in series with the bridge circuit, a differential amplifier, a voltage comparator, and a display means. C, 2 on one side of the bridge circuit
By using both ends of one of the resistors as input terminals, the detection resistance is small, and the voltage applied to the circuit under test is
It is possible to realize a continuity tester that uses a small amount of current, has good workability, and does not impair the reliability of the device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a first embodiment of the present invention. FIG. 2 is a circuit diagram of a second embodiment of the present invention. 1 is an input circuit, 2 is a differential amplifier, 3 is a voltage comparator, 4 is a buzzer, 5 to 11 are resistors, 12.13 is an input terminal to be measured during a continuity test, 14.15 is an output of the presigi circuit,
16.17 is the output of the differential amplifier. 18.19 are transistors forming a differential amplifier. 20 is a battery, 22 is an IO operational amplifier, 23 is a variable resistor for zero point adjustment, 24 is the output of the operational amplifier 22, 25.26 is a resistor for creating a reference voltage for voltage comparator 3, 27 is a voltage This is the reference voltage input for comparator 3. Patent applicant Representative of Sigma Technology Industry Co., Ltd. Kami 1) Kaoru (9) Ri l Figure

Claims (1)

[Scope of Claims] 1. A bridge circuit in which one of the four sides is composed of at least two resistors, a resistor connected in series to the bridge circuit, a differential amplifier, a voltage comparator, and a display means, υ; A continuity tester whose % indication is when both ends of one of the two resistors on one side of a bridge circuit are used as input terminals. 2. Patent 3, in which the bridge circuit is configured so that the magnitude of the output potential is reversed when the input terminal is open and when a resistance value lower than the detection resistor is connected. The continuity tester according to claim 1, wherein a bias voltage is applied to the output of the zero time differential amplifier. 4. Bridge circuit κ The series-connected resistor consists of two resistors and is connected to both ends of the bridge circuit. #f The continuity tester according to claim 1. 5. The continuity tester according to claim 1, wherein the display means is a buzzer.