JPH02259581A - Detecting circuit for terminal connection state of circuit element measuring instrument - Google Patents

Abstract

PURPOSE:To confirm an electrical connection and to prevent a measurement mistake caused from the connection abnormality by appropriately changing over five switches provided in a circuit and performing a continuity test between each measuring terminal and a measuring element. CONSTITUTION:For the continuity test between the measuring terminals 11 and 12, the switches 3 to 7 are connected as specified, then the signal of a signal source 1 is connected to the terminal 11 and the terminal 12 is connected to a current/voltage converter 8, respectively, and further the terminals 11, 12 are connected to a voltage detector 9. For the continuity test between the measuring terminals 13 and 14, the signal source 1 is connected to the termi nal 13 and the terminal 14 is connected to the converter 8, respectively, by changing over the switches 3-7, and further the terminals 13, 14 are connected to the detector 9. Then, the continuity test is performed between the terminals 11, 12 connected to a terminal 20A of the measuring element 20 and connecting terminals 21, 22 to measure an impedance of the connection passway. Next, the same test and measurement are made for the terminals 13, 14 connected to a terminal 20B and connecting terminals 23, 24, then the correct or incorrect connection is decided from the continuity test result and the measured value of the impedance. When the connection is correct, the measurement for the element 20 is started.

Description

Detailed Description of the Invention (a) Technical Field of the Invention The present invention is directed to a circuit element measuring instrument having a four-terminal configuration, in which the electrical contact between each measuring terminal and the measuring element is confirmed, and the electrical contact between the measuring terminal and the measuring element is confirmed. This allows the impedance of the connection path to be measured.

(1)) Prior Art and Problems Next, the configuration of a four-terminal circuit element measuring instrument will be described with reference to FIG.

1 in Figure 5 is a signal source for measurement, 2 is a resistor for current limiting,
8 is a current/voltage converter, 9 is a voltage detector, 11 to 14 are measurement terminals, 20 is a measurement element, and 21 to 24 are connection terminals.

The current/pressure converter 8 includes an operational amplifier 8A and a reference resistor 8B.
, and a differential amplifier 80''C', and the voltage detector 9 is composed of a differential amplifier.

In FIG. 5, the measurement terminal 11 is connected to the terminal 2OA of the measurement element 20.
12, connect the measurement terminals 13 and 14 to the terminal 208 of the measurement element 20, supply the signal from the signal source 1 to the measurement terminal 11, and send the signal current flowing through the measurement element 20 to the measurement terminal 13.
- The current/voltage converter 8 connected to the measurement terminal 14 detects the voltage, and the voltage between the terminals of the measurement element 20 is detected by the voltage detection B9 connected to the measurement terminals 12 and 13.

A measurement jig or the like is used to connect the measurement terminals 11 to 14 and the measurement element 20 using a cable or the like.

In FIG. 5, connection terminals from the measurement terminals 11 to 14 to the measurement element 20 are designated as 21 to 24.

When connected normally, the measurement terminal 11 and the connection terminal 21 and the measurement terminal 12 and the connection terminal 22 have the same potential, and are connected to the terminal 2OA of the measurement element 20. Also,
The measurement terminal 13 and the connection terminal 23 and the measurement terminal 14 and the connection terminal 24 have the same potential, respectively, and the terminal 20 of the measurement element 20
Connected to 8.

However, due to cable breakage or poor contact, the connection terminal 2
1 to 24 may not be reliably connected to the measuring element 20, and correct measurement may not be possible.

For example, if only the wire between the measurement terminal 11 and the connection terminal 21 is disconnected, the measurement signal is no longer supplied to the measurement element 20, and the voltage between both terminals of the measurement element 20 is detected as OV.
The signal current flowing through the measuring element 20 is detected as OA,
Measured as impedance indeterminate.

Further, if only the connection terminal 24 is disconnected, the feedback path of the operational amplifier 8A is disconnected, and the terminal 208 of the measurement element 20 cannot be maintained at the virtual ground potential.

In this state, the input impedance of the measuring terminal 13 on the measuring device side is a certain value, so a minute current flows from the connecting terminal 23 to the measuring terminal 13, the voltage between the terminals of the measuring element 20 shows a certain finite value, and the measuring terminal 14 is open, no feedback current flows through the reference resistor 8B, and the signal current becomes O.
Detected as A.

Therefore, the measurement impedance becomes infinite and a correct measurement value cannot be obtained.

Furthermore, if only the wire between the measurement terminal 12 and the connection terminal 22 is disconnected, the measurement terminal 12 becomes open and the measurement element 20
The voltage between the terminals of is detected as OV, the signal current flowing through the measuring element 20 is detected as a certain finite value, and the impedance is measured as 0Ω.

Further, if only the connection terminal 23 and the measurement terminal 13 are disconnected, the feedback path of the operational amplifier 8A is disconnected, and a certain finite signal current determined by the signal generated by the operational amplifier 8A flows to the reference resistor 8B. The voltage at the measurement terminal 12 has a value determined by this signal current.

Therefore, in this case, a certain value of the measurement impedance is obtained, but it is a value that does not match the impedance of the measurement element 20.

These are abnormal connection states that occur independently, but they may also occur in combination.

(C) Purpose of the Invention The present invention provides a measuring terminal 11 and a connecting terminal 21 connected to a terminal 2OA of a measuring element 20, a measuring terminal 12 and a connecting terminal 2 connected to a terminal 2OA of a measuring element 20,
Regarding 2, a continuity test and the impedance of the connection path are measured, and then the measurement terminal 13 and the connection terminal 23 connected to the terminal 208 of the measurement element 20, and the connection terminal 24 and the measurement terminal 1 are connected.
Regarding 4, the terminal connection status of the circuit element measuring instrument is to measure the impedance of the connection path through a continuity test and determine whether the connection is correct based on the continuity test result and the measured value of the impedance of the connection path! The purpose is to provide a detection circuit.

(d) Examples of the invention Next, a block diagram of an embodiment according to the present invention is shown in FIG.

3 to 7 in Figure 1 are switches, and the other parts are switches 5 to 7.
Same as the figure.

The switch 3 is connected to the output of the signal source 1 through the resistor 2, the terminal 3A of the switch 3 is connected to the measurement terminal 11, and the terminal 3B is connected to the measurement terminal 13.

Switches 4 and 5 operate in conjunction, and the measurement terminals 11 and 12
or between the measurement terminals 13 and 14.

When switches 4 and 5 are set to terminal A, measurement terminals 12 and
When the voltage between the measurement terminals 11 and 13 is detected and the switches 4 and 5 are set to Blm, the voltage between the measurement terminals 11 and 12 can be detected.

When the switches 4 and 5 are set to terminal C measurement, the voltage between the measurement terminals 13 and 14 can be detected. Let this detected voltage be EL.

Switch 6 is connected to one end of reference resistor 8B. Terminal 6A of switch 6 is connected to terminal 14, and terminal 6B is connected to measurement terminal 12.

Switch 7 is connected to the input terminal of operational amplifier 8A. Terminal 7A of switch 7 is connected to measurement terminal 13, and terminal 7B is connected to one end of reference resistor 8B forming a feedback circuit of operational amplifier 8A.

Note that the terminal connections of switches 3 to 7 in FIG. 1 show the state for normal measurement.

Next, referring to FIG. 2, we will explain the case of conducting a continuity test between the measurement terminals 11 and 12. The two switches 3 to 7 are the second
Position it as shown.

If the connecting terminal 21 and the connecting terminal 22 are connected correctly at the terminal 2OA of the measuring element 20, the measurement signal current flows from the terminal 3A of the switch 3 to the measuring terminal 11 → the connecting terminal 21.
−→Connection terminal 22→Measurement terminal 12→Terminal 6 of switch 6
It flows through path B.

A reference resistor 8B is connected to the operational amplifier 8A by a switch 7 as a feedback resistor of the operational amplifier 8A, and the terminal 6B of the switch 6, that is, the measurement terminal 12 becomes a virtual ground potential, and the output of the differential amplifier 8C , voltage E is output.

This voltage E, is expressed by the formula %, where ZH is the sum of the impedance of the cable etc. and the connection impedance of the connecting terminals 21 and 22. Here, Rr is the resistance value of the reference resistor 8B, and Rs is the resistance of the resistor 2. The value Es is the voltage of the signal source 1.

Further, the current 11 flowing at this time is expressed by equation (2).

ii=-E,,/Rr・・・・・・・・・・・・・
(2) At this time, the voltage E between the measurement terminals 11 and 12 is detected by the switches 4 and 5 as the output Evl of the voltage detector 9. Ru.

Connection path impedance ZH between measurement terminals 11 and 12
is expressed by equation (3).

Z, l=E□/ it = (E-1/ Ell) ×Rr・・−・−+・+
(3) Therefore, if the reference resistance 8B is known, Z□ can be easily calculated from the detected values of EB and Ell.

Next, with reference to FIG. 3, a case of conducting a continuity test between the measurement terminals 13 and 14 will be described.

Switches 3-7 are placed in the positions shown in FIG.

When the connecting terminals 23 and 24 are correctly connected to the terminal 208 of the measuring element 20, the current 12 flows from the terminal 3B of the switch 3 to the measuring terminal 13 → connecting terminal 23 → connecting terminal 24 → measuring terminal 14 → It flows through the connection path of the terminal 6A of the switch 6.

A reference resistor 8B is connected to the operational amplifier 8A by a switch 7 as a feedback resistor of the operational amplifier 8A, and 1. The terminal 6A of the switch 6, that is, the connection terminal 14 becomes a virtual ground potential, and the signal voltage of Ell is outputted from the differential amplifier 8C for detecting the terminal voltage of the reference resistor 8B. This Ell is expressed by equation (4), where ZL is the total impedance of the impedance of the measurement cable etc. and the connection impedance of the connection terminals 23 and 24.

E12= (Rr/ (R5+ZL)l XEs...
(4) Also, the current 12 flowing at this time is expressed by equation (5).

i z = E lx/Rr・・・・・・・・・・
・・・・・・・・・・・・・・・・・・・・・+5) At this time, the voltage EL between the measurement terminals 13 and 14 is changed to the output Evi of the voltage detector 9 by the switches 4 and 5. Detected as .

Connection path impedance ZL between measurement terminals 13 and 14
is expressed by equation (6).

ZL=Et,/12=(E, 2./El2)XRr・・・・・・・・・
(6) Therefore, if the reference resistance 8B is known, ZL can be easily calculated from the detected values of Ev2 and El2.

If the connection path impedance becomes high at the connection point with the measurement element 20 due to a break in the cable or an increase in contact resistance, the detected E or El2
The voltage will be lower than when connected normally.

This can be easily understood from equations (1) and (4).

Using the voltage E1m and voltage E12 detected in this way, it is possible to judge whether the continuity test is good or bad.

For example, in a continuity test between the measurement terminals 11 and 12, if the contact resistance between the connection terminals 21 and 22 becomes large, the flowing signal current i decreases, and the voltage EH1 between the measurement terminals 11 and 12, that is, El , becomes a large value, and the differential amplifier 8
The output voltage E11 of C becomes a small value.

When the detected voltage EB and voltage Ell are substituted into equation (3), Z)l becomes a larger value than in the case of normal connection, and the connection path impedance ZH can be known.

In the same way, the impedance zL of the connection path can be found for the measurement terminals 13 and 14 as well.

By comparing Z□ and zL measured in the continuity tests shown in FIGS. 2 and 3 with reference values for correct connection, it is possible to determine whether or not the connection is correct.

When the connections are correct, the switches 3 to 7 are placed in the positions shown in FIG. 1, and measurement of the measuring element 20 begins.

By providing the switches 3 to 7, the voltage between the measurement terminals 11 and 12 and the measurement terminals 13 and 14 is detected by a continuity test, and the impedance of the connection path is determined from the flowing current and the voltage between the terminals, and it is confirmed that the connection is correct. If it is determined that the connection is not correct, the connection abnormality can be displayed on a display device installed in the device, and the measured value of the impedance of the connection path between Z□ and ZL can also be displayed.

Next, a block diagram of another embodiment according to the present invention is shown in FIG.

In FIG. 4, the switches 4 and 5 and voltage detector 9 in FIG. 1 are replaced with differential amplifiers 9A to 9C and a switch 9D.

The differential amplifier 9A detects the voltage between the measurement terminals 11 and 12, and the differential amplifier 9C detects the voltage between the measurement terminals 13 and 14.

The switch 9D switches each detection voltage to detect the voltage Ev.

The operation in FIG. 4 is exactly the same as that in FIG. 1, but according to FIG.
9c can be arranged, and high impedance between terminals can be obtained.

(e) Effects of the Invention According to this invention, it is possible to perform a continuity test to check the connection state between each measurement terminal and the measurement element by setting the switch, so it is possible to check the electrical connection. , it is possible to prevent measurement errors due to connection abnormalities.

Furthermore, since the connection path impedance between the measurement terminal and the connection terminal can be measured, the impedance of the connection path can also be reported.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an embodiment according to the present invention, Fig. 2 is a connection diagram for conducting a continuity test between measurement terminals 11 and 12, and Fig. 3 is a continuity diagram for conducting a continuity test between measurement terminals 13 and 14. FIG. 4 is a configuration diagram of another embodiment according to the present invention.
FIG. 5 is a configuration diagram of a circuit element measuring instrument having a four-terminal configuration. 1... Signal source, 2... Resistor, 3-7.
...Switch, 8...Current/voltage converter, 8A...Operation amplifier, 8B...Reference resistor, 8C...Differential amplifier , 9...Voltage detector, 11-14...Measurement terminal, 20...
...Measuring element, 21-24... Connection terminal. Agent Patent Attorney Kin Omata District Switch Switch Switch Diagram Diagram

Claims (1)

[Claims] 1. A first measurement terminal (11) and a second measurement terminal (12) are connected to the first terminal (20A) of the measurement element (20),
The third measurement terminal (13) and the fourth measurement terminal (14) are connected to the second terminal (208) of the measurement element (20), and the signal from the signal source (1) is transferred to the first measurement terminal (11). ), and the signal current flowing through the measuring element (20) is supplied to the third measuring terminal (1
3) and a current/voltage converter (8) connected to the fourth measurement terminal (14), and detect the voltage between the terminals of the measurement element (20) between the second measurement terminal (12) and the third measurement terminal (14). Terminal (
In a circuit element measuring device that detects with a voltage detector (9) connected to a signal source (1), a continuity test between a first measurement terminal (11) and a second measurement terminal (12) is performed using a signal source (1). Connect the signal to the first measurement terminal (11), connect the second measurement terminal (12) to the current/voltage converter (8), and connect the signal between the first measurement terminal (11) and the second measurement terminal (12) to the voltage detector (9), and for continuity testing between the third measurement terminal (13) and the fourth measurement terminal (14), the signal from the signal source (1) is connected to the third measurement terminal (13) and the fourth measurement terminal (14). Connect to the measurement terminal (13), connect the fourth measurement terminal (14) to the current/voltage converter (8), and connect the third measurement terminal (13) and the fourth measurement terminal (14) to voltage detection. A terminal connection state detection circuit for a circuit element measuring device, characterized in that the circuit is connected to a device (9).