JP2000111593A - Measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a measuring device capable of performing contact check without caring the contact on-resistance of a switch. SOLUTION: In a measuring device for measuring an object to be measured 1 by contacting, arranged are a constant current source 26 sending a constant current for contact check from a power source 23 for measurement and another system power source and switch parts 21 and 22 connecting to the wire for measuring the object to be measured and to the constant current source 26 and turning on when checking the wire. Contact check is done by resistors R1 to R4 in the wiring.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device for measuring an object to be measured, for example, a resistance, and more particularly to a measuring device having a function of diagnosing a connection state of a measurement wiring.

[0002]

2. Description of the Related Art A conventional measuring device for measuring resistance is shown in FIG. The figure shows a reset state.

In the drawing, reference numeral 1 denotes a resistance to be measured, a wiring portion 2,
3 is connected to the resistance 1 to be measured. The wiring section 2 includes wiring resistances R1 and R2, and the wiring section 3 includes wiring resistances R3 and R4.
Consists of One end of each of the wiring resistances R1 and R2 is the resistance 1 to be measured.
And the contact resistance with the resistance under test 1 is also included. One end of each of the wiring resistors R3 and R4 is connected to the other end of the measured resistor 1, and the contact resistance with the measured resistor 1 is also included. The measuring device 100 is connected to the wiring units 2 and 3 and measures the resistance 1 to be measured.

Hereinafter, the configuration of the measuring apparatus 100 will be described.
The switch unit 4 includes switches SW1 to SW4, and is connected to the wiring units 2 and 3 for switching. The switch SW1 is
The switch SW2 is connected to the other end of the wiring resistance R2, the switch SW3 is connected to the other end of the wiring resistance R3, and the switch SW4 is connected to the other end of the wiring resistance R4.
To the other end.

[0005] The switch units 5 and 6 are connected to the switch unit 4 and are turned on / off. The switch unit 5 includes a switch SW
5, SW6, and the switch unit 6 includes a switch SW.
7, SW8. The switch SW5 is a switch SW5.
1, and the switch SW6 is switched to the switch SW2.
The switch SW7 is switched by the switch SW3, and the switch SW8 is switched by the switch SW4.

The constant current source 7 is connected to the switch section 4 and outputs a constant current flowing through the resistance 1 to be measured. One end of the constant current source 7 is switched by the switch SW1, and the other end is the switch S1.
It is switched by W4 and grounded.

The differential amplifier 8 is connected to the switch unit 4,
Output to an A / D converter (not shown). Differential amplifier 8
One input terminal is switched by a switch SW2, and the other input terminal is switched by a switch SW3.

[0008] The constant current source 9 is connected to the switches 5 and 6, and outputs a constant current for contact check. The constant current source 9 has one end connected to the other ends of the switches SW5 and SW7, the other end connected to the switches SW6 and SW8,
Ground.

The comparator 10 has one input terminal connected to one end of the constant current source 9 and the other input terminal connected to the reference voltage 11, and outputs a comparison result.

The CPU 12 receives the output of the comparator 10, determines good / bad, and outputs it to the signal output 13 and the display 14.

The operation of such an apparatus will be described. First, the measuring operation of the measured resistance 1 will be described. Switch SW
1 and SW4 are switched to the constant current source 7, and switches SW2 and SW2 are switched.
SW3 is switched to the differential amplifier 8. Then, the constant current source 7 allows a current to flow through the resistance 1 to be measured. The differential amplifier 8 amplifies the voltage generated at both ends of the resistance under test 1 and outputs the amplified voltage to the A / D converter.

Next, a contact check operation will be described. Switch SW1 to switch SW5, switch SW2 to switch SW6, switch SW
3 is switched to a switch SW7, and the switch SW4 is switched to a switch SW8.

The switches SW5 and SW6 are turned on, and the switches SW7 and SW8 are kept off. Then, the constant current source 9 causes a current to flow through the wiring resistors R1 and R2. The comparator 10 compares the voltage generated by the wiring resistances R1 and R2 with the reference voltage 11, and outputs the comparison result to the CPU 12. The CPU 12 determines the wiring resistances R1 and R2, that is, whether the wiring is good or bad, and outputs the signal output 13 and the display 1
4 and the judgment result is output.

Similarly, the switches SW5 and SW6 are turned off, and the switches SW7 and SW8 are turned on. Then, the constant current source 9 causes a current to flow through the wiring resistors R3 and R4. The comparator 10 compares the voltage generated by the wiring resistances R3 and R4 with the reference voltage 11, and outputs the comparison result to the CPU 12. The CPU 12 sets the wiring resistances R3 and R4,
The pass / fail of the wiring is determined, and the determination result is output to the signal output 13 and the display 14.

[0015]

In such a device,
In order to reduce the compliance voltage of the constant current sources 7 and 9 (suppress the power consumption), it is necessary to reduce the on-resistance of the switch unit 4. When the resistance 1 to be measured has a low resistance, a current of about 200 mA flows from the constant current source 7, so that the power consumed by the switch unit 4 becomes heat inside the device, thereby increasing the temperature. The effect appears as a drift of the measured value. Therefore, a mechanical relay having a small on-resistance is used for the switch unit 4.

For example, when a large amount is handled at a high speed as in a test line for chip resistance, erroneous measurement due to fatigue or disconnection of the contact surface of the measurement probe becomes a problem. Therefore, a contact check is performed for each measurement to diagnose the connection state, thereby maintaining the reliability of the measurement.

However, when switching between the measurement state and the contact check state, it is necessary to wait until the switch section 4 is stabilized. In the case of a mechanical relay, the stabilization time is as long as several milliseconds, which hinders a large amount of measurement at high speed.

In the case of a mechanical relay, the service life becomes a problem, and periodic maintenance is required.

An object of the present invention is to realize a measuring device capable of performing a contact check without regard to the on-resistance of a switch.

[0020]

SUMMARY OF THE INVENTION The present invention relates to a measuring apparatus connected to an object to be measured for performing a measurement, comprising: a constant current source for supplying a constant current for contact check by a power supply for measurement and a power supply of another system; A switch section connected to the measurement wiring of the object to be measured, connected to the constant current source, and turned on when checking the wiring, and performing a contact check by the resistance of the wiring. It is.

In the present invention, when checking the wiring for measurement, the switch section is turned on, a constant current is supplied to the wiring by a constant current source, and a contact check is performed based on a voltage due to the resistance of the wiring.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. Here, the same components as those in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

In the figure, switch sections 21 and 22 are connected to wiring sections 2 and 3, respectively, and are turned on / off. The switch unit 21 includes switches SW9 and S
The switch unit 22 includes switches SW11 and SW12 that are MOSFETs. Switch SW
The switch 9 has one end connected to the other end of the wiring resistor R1 and the switch S
W10 has one end connected to the other end of the wiring resistor R2. The switch SW11 has one end connected to the other end of the wiring resistor R3,
The switch SW12 has one end connected to the other end of the wiring resistor R4.

The constant current source 23 is connected to the wiring parts 2 and 3,
A constant current flowing through the resistance to be measured 1 is output. Constant current source 23
Has one end connected to the other end of the wiring resistance R1, the other end connected to the other end of the wiring resistance R4, and grounded to the ground 24.

The differential amplifier 25 is connected to the wiring sections 2 and 3 and outputs the result to an A / D converter (not shown). The differential amplifier 25 has one input terminal connected to the other end of the wiring resistor R2,
The other input terminal is connected to the other end of the wiring resistor R3.

The constant current source 26 is connected to the switch units 21 and 22 and outputs a constant current of “50 mA” for contact check by a power supply of a different system from the constant current source 23. The constant current source 26 has one end connected to the other ends of the switches SW9 and SW11, the other end connected to the other ends of the switches SW10 and SW12, and grounded to a ground 27 different from the ground 24.

The comparator 28 has one input terminal connected to one end of the constant current source 26 and the other input terminal connected to the reference voltage 29.
And output the comparison result. The reference voltage 29 is grounded to the ground 27.

The CPU 30 receives the output of the comparator 28, determines good / bad, and outputs it to the signal output 31 and the display 32.

The structure of the constant current source 23 will be described in more detail with reference to FIG. In the figure, a resistor R5 has a resistance value "5".
Ω ”, and one end is connected to“ 5 V. ”
The drain is connected to the other end of the resistor R5, and a constant current is output from the source. The amplifier 232 has the − terminal connected to the other end of the resistor R5, and the output terminal connected to the gate of the FET 231. The switch 233 switches between “4.999 V” and “4 V” and outputs the same to the + terminal of the amplifier 232.

The operation of such a device will be described below.
First, the measuring operation of the measured resistance 1 will be described. Switch S
W9 to SW12 are kept off. Then, the switch 233 selects “4 V” and outputs “200 V” from the constant current source 23.
mA "constant current flows through the resistance 1 to be measured.
Amplifies the voltage generated across the resistance 1 to be measured, and A /
Output to D converter.

Next, the contact check operation will be described. The switches SW9 and SW10 are turned on, and the switch S
W11 and SW12 are kept off. Switch 233
Selects “4.999V”, and the constant current source 23 selects “0.299V”.
A constant current of 0.2 mA is output.
The constant current of A ″ flows through the wiring resistance R1, the measured resistance 1, and the wiring resistance R4, and flows to the ground 24. The constant current source 26.
The constant current of “50 mA” flows through the switch SW9, the wiring resistance R1, the wiring resistance R2, and the switch SW10, and flows to the ground 27.

Usually, the accuracy of the contact check level is not so required, and may be 1%. Therefore, when the constant current for contact check is “50 mA”, it is sufficient to set the constant current for measurement to about “0.5 mA”.

The comparator 28 has a wiring resistance R
1 and R2 are compared with the reference voltage 29, and the comparison result is output to the CPU 30. The CPU 30
The wiring resistances R1 and R2, that is, whether the wiring is good or bad, are determined, and the determination result is output to the signal output 31 and the display 32.

Similarly, the switches SW9 and SW10 are turned off, and the switches SW11 and SW12 are turned on. The constant current of “0.2 mA” from the constant current source 23 flows through the wiring resistance R1, the measured resistance 1, and the wiring resistance R4, and flows to the ground 24. The constant current of “50 mA” of the constant current source 26 flows through the switch SW11, the wiring resistance R3, the wiring resistance R4, and the switch SW12, and flows to the ground 27.

The comparator 28 determines the wiring resistance R
3, the voltage generated by R4 is compared with the reference voltage 29, and the comparison result is output to the CPU 30. The CPU 30
The wiring resistances R3 and R4, that is, whether the wiring is good or bad, are determined, and the determination result is output to the signal output 31 and the display 32.

As described above, the constant current source 23 and the constant current source 26
Therefore, the contact check can be performed for each measurement without switching the constant current source 23 for measurement with a switch. That is, there is no need to worry about the on-resistance of the switch.

In addition, there is no need to use a mechanical relay, and there is no need for a switch stabilization time at the time of switching.
High-speed measurement becomes possible. In addition, maintenance-free can be achieved because no life component is used.

The present invention is not limited to this, but may be as follows. Although the configuration for comparing the reference voltage 29 with the voltage generated by the wiring resistance has been described,
The reference voltage may be output by a D / A converter. In this case, the contact check level can be changed, and it is possible to easily cope with a measuring device having a different wiring resistance.

Although the configuration for comparison by the comparator 28 has been described, the voltage generated by the wiring resistance is input to the A / D converter, and the CPU determines whether the wiring is good or not based on the output of the A / D converter. It may be configured.

As the measuring device, the device for measuring the resistance value of the resistor as the object to be measured has been described, but another measuring device may be used. For example, the capacitance of the capacitor may be determined.

In the case of a capacitor, the measurement can be performed with the same configuration as that for measuring the resistance. That is, assuming that it takes time T for a capacitor having a capacitance of C to be charged with a constant current I and for the voltage across the capacitor to reach a predetermined voltage value V, C = T · It can be determined by I / V.

Alternatively, as another configuration, a sine wave AC voltage of a predetermined frequency is applied from an AC power supply to one of the capacitors, a current is taken in from the other, and only a voltage having a phase of 90 degrees is passed through a current-voltage conversion circuit and a phase detection circuit. Take out,
It is also possible to adopt a configuration in which a DC voltage is converted by an AC / DC conversion circuit, then converted into a digital value, and a capacitance value is calculated by the CPU based on the digital value. In such a case, the wiring resistances R2, R3
Is a configuration required only by contact check.

[0043]

According to the present invention, the following effects can be obtained. Since the power supply system of the constant current source for contact check is separated from the power supply for measurement, the contact check can be performed for each measurement without switching the measurement system with a switch. That is, there is no need to worry about the on-resistance of the switch.

In addition, there is no need to use a mechanical relay, and there is no need for a switch stabilization time at the time of switching.
High-speed measurement becomes possible. In addition, maintenance-free can be achieved because no life component is used.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a configuration diagram of a constant current source 23 of the device shown in FIG.

FIG. 3 is a diagram showing a configuration of a conventional measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Resistance to be measured 21 Switch part 22 Switch part 23 Constant current source 25 Differential amplifier 26 Constant current source R1-R4 Wiring resistance

Claims (4)

[Claims] 1. A measuring apparatus connected to an object to be measured for performing measurement, comprising: a constant current source for supplying a constant current for contact check by a power supply for measurement separately from a power supply for measurement; A measuring device, comprising: a switch unit connected to a wiring, connected to the constant current source, and turned on when checking the wiring, and performing a contact check by the resistance of the wiring. 2. A measuring apparatus for measuring an object to be measured, wherein: a first constant current source for supplying a constant current to the object to be measured by first and second wirings connected to the object to be measured; A differential amplifier for measuring a voltage difference between both ends by third and fourth wirings connected to an object; and a second current for flowing a constant current for contact check by a power supply of a different system from the first constant current source. A constant current source, connected to the first and third wires connected to one end of the device under test, and connected to the second constant current source, and turned on when checking the first and third wires; A first switch unit, connected to the second and fourth wirings connected to the other end of the object to be measured, and connected to the second constant current source to check the second and fourth wirings; At the time of contact check. A source of constant current is within the error range of the contact check, measuring device which is characterized in that the contact check by the resistance of the first to fourth wiring. 3. The device according to claim 2, wherein the first switch unit and the second switch unit are configured by FETs.
The measuring device as described. 4. The measuring device according to claim 1, wherein the object to be measured is a resistance.