JPH02259582A - Detecting circuit for terminal connection state of circuit element measuring instrument - Google Patents

Abstract

PURPOSE:To prevent a measuring mistake caused from an electrical connection abnormality by performing a continuity test and an impedance measurement in the manner of opening or short-circuiting switches which are provided between a 1st and 2nd measuring terminals and between a 3rd and 4th measuring terminals. CONSTITUTION:The switches 4, are provided for short-circuiting/opening the connections between the measuring terminals 11, 12 and between the measuring terminals 13, 14. By the switches 3, 6, 7, a signal source 1 is connected to the terminal 11 and the terminal 12 is connected to a current/voltage converter 8, and also the terminals 11, 12 are connected to a voltage detector 9, then the switch 4 is short-circuited/opened to perform the continuity test. Next, by changing over the switches 3, 6, the signal source 1 is connected to the terminal 13, the terminal 14 is connected to the converter 8 and the terminals 13, 14 are connected to the detector 9, respectively, then the continuity test between the measuring terminals 13, 14 is made by short-circuiting/opening the switch 5. At this time, if the resistance value of a reference resistor 8B and the voltage of the signal source 1 are already known, the impedance of a connection passway can be easily calculated from values of each detected voltage at the time when the switches 4, 5 are short-circuited/opened, thereby the connection between the terminals can be confirmed.

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 connection to the measuring element is confirmed. This allows the impedance of the connection path to be measured.

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

1 in Figure 4 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/voltage converter 8 includes an operational amplifier 8A and a reference resistor 8B.
, a differential amplifier 8C''ct#, and the voltage detector 9 is composed of a differential amplifier.

In FIG. 4, 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 20B 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 detector 9 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. 4, 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 B.

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 mold pressure between both terminals of the measurement element 20 is detected as 0.
The signal current flowing through the measuring element 20 is detected as QA,
Measured as impedance indeterminate.

Further, if only the connection terminal 24 and the measurement terminal 14 are disconnected, the feedback path of the operational amplifier 8A is disconnected, and the terminal 20B 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.

In addition, 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 was conducted and the impedance of the connection path was measured when the switch provided between the measurement terminals 11 and 12 was opened and when it was short-circuited, and then the impedance of the connection path was measured.
Regarding the measurement terminal 13 and the connection terminal 23 connected to 0B, and the connection terminal 24 and the measurement terminal 14, conduction tests and connection path tests were performed when the switch provided between the measurement terminals 13 and 14 was opened and when it was short-circuited. Measure the impedance, and based on the continuity test results and the measured value of the impedance of the connection path,
The present invention aims to provide a terminal connection state detection circuit for a circuit element measuring device that determines whether the connection is correct.

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

3N7 in Figure 1 is a switch, and the other parts are the 4th
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.

Switch 4 is provided between measurement terminals 11 and 12, and switch 5 is provided between measurement terminals 13 and 14.

Switch 6 is connected to one end of reference resistor 8B. The terminal 6A of the switch 6 is connected to the terminal 14, and the terminal 6B is connected to the 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, with reference to FIG. 2, a case of conducting a continuity test between the measurement terminals 11 and 12 will be described.

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

If the connection terminal 21 and the connection terminal 22 are connected correctly at the terminal 2OA of the measurement element 20, the measurement signal current i is
From terminal 3A of switch 3, measurement terminal 11 → connection terminal 2
1→Connecting terminal 22-QIJJ constant terminal 12→Terminal 6B of 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 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 Elf is calculated using the following equation (1), where Zll is the sum of the impedance of the cable, etc. and the connection impedance of the connection terminals 21 and 22. Here, Rr is the resistance value of the reference resistor 8B, R8 is the resistance value of the resistor 2, Es is the voltage of the signal source 1.

Expanding equation (1) and rewriting it as an equation for finding ZH, we get equation (
2).

Zn-(Es/Eat)XRr-Rs----
-(2) Next, short-circuit switch 4.

The signal current 11m flowing at this time is connected from the terminal 3A of the switch 3 because the measurement terminals 11 and 12 are short-circuited by the switch 4 regardless of the connection path of the measurement terminal 11 → connection terminal 21 → connection terminal 22 → measurement terminal 12. It flows through switch 4 to terminal 6B of switch 6, and the output of differential amplifier 8C has E, 1 . signal voltage is detected. Eo at this time,
is expressed by equation (3).

-E, 1. =(Rr/R8)XEs・・・・・・・・・
(3) When formula (3) is expanded and rewritten as a formula for determining R8, formula (4) is obtained.

Rs= (Es/Etts) XRr”・・−
-(43 Substituting equation (4) into equation (2) yields equation (5).

Zs = ((1/Eat) −(1/Ell−
))XEsXRr・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・(5) Standard resistance 8B
If Es of the signal source 1 is a predetermined value, the detected voltage Ell when the switch 4 is open, and the detected voltage E21 when the switch 4 is shorted. From the values of , Z and l can be easily calculated.

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 20B 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 the terminal 6A of the switch 6, that is, the connection terminal 14 becomes a virtual ground potential, and the terminal voltage of the reference resistor 8B is The signal voltage of El2 is outputted to the output of the differential amplifier 8C for detection. This voltage Eig is expressed by equation (6), 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.

E+z= (Rr/ (R5+ZL)l XEs...
(6) When formula (6) is expanded and rewritten as a formula for determining zL, formula (7) is obtained.

ZL = (Es/-Eiz)XRr-FLs-・-・
(7) Next, short-circuit switch 5.

The signal current i□ flowing at this time is independent of the connection path of measurement terminal 13 → connection terminal 23 → connection terminal 24 → measurement terminal 14, because measurement terminals 13 and 14 are short-circuited by switch 5, and terminal 3B of switch 3 , passes through the switch 5, flows through the path of the terminal 6A of the switch 6, and the output of the differential amplifier 8C is E, □.

signal voltage is detected.

El2 at this time. is expressed by equation (8).

E I2. = (Rr/Rs)
--(8) When formula (8) is expanded and rewritten as a formula for determining Rs, formula (9) is obtained.

Rs = (Es / E12s) X Rr-
---(9) Substituting equation (9) into equation (7), equation (10
)become.

zL=((x/-Eiz)-(1/-El2.))XE
sXRr・・・・・・・・・・・・・・・・・・
(10) If the reference resistor 8B and the Es of the signal source 1 are known values, the detection voltage E12 when the switch 5 is opened and the voltage when the switch 5 is shorted are Detection voltage E12. ZL can be easily calculated from the value of .

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 EIK or El
The voltage at No. 2 will be lower than when connected normally. This can be easily understood from equations (1) and (6).

By comparing ZH and Zt 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.

As a simple means of continuity test, the voltage Es
, resistance Rs, and resistance Rr are known values, then switch 4.
Continuity testing can be performed without providing 5.

El by equation (3) or equation (8) in advance.

Calculate and connect and measure EL as shown in Figure 2.
S and E6. The determination can be made by comparing E,2 and Els, which are connected and measured as shown in FIG.

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 ZL4 and ZL can also be displayed.

(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 a circuit element measuring instrument having a four-terminal configuration. 1... Signal source, 2... Resistor, 3-7.
...Switch, 8...Current/pressure 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 Komata Figure Voltage Detector Voltage Detector Voltage Detector

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 (20B) 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 voltage detector (9) connected to a voltage detector (13), a first switch (4 ) and a second switch (5) that short-circuits and opens between the third measurement terminal (13) and the fourth measurement terminal (14), When conducting a continuity test between measurement terminals (12), connect the signal from the signal source (1) to the first measurement terminal (11), and connect the second measurement terminal (12) to the current/voltage converter ( 8) and the first measurement terminal (1
1) and the second measurement terminal (12) are connected to the voltage detector (9), the first switch (4) is short-circuited and opened, and the third terminal (13) and the fourth terminal (14) are connected to the voltage detector (9). ), connect the signal from the signal source (1) to the third measurement terminal (13), and connect the fourth measurement terminal (14) to the current/voltage converter (8). Then, connect the third measurement terminal (13) and the fourth measurement terminal (14) to the voltage detector (9),
A terminal connection state detection circuit for a circuit element measuring instrument, characterized in that a second switch (5) is short-circuited and opened.