JPH0814591B2 - Circuit element measuring device terminal connection state detection circuit - Google Patents

Description

Description: (a) Technical Field of the Invention The present invention relates to a circuit element measuring instrument having a four-terminal configuration,
The electrical contact between each measuring terminal and the measuring element is confirmed, and the impedance of the connection path connected to the measuring element can be measured.

(B) Prior Art and Problems Next, with reference to FIG. 4, the configuration of a circuit element measuring instrument having a four-terminal configuration will be described.

In FIG. 4, 1 is a signal source for measurement, 2 is a resistor for limiting current, 8 is a current / voltage converter, 9 is a voltage detector, 11 to 14 are measuring terminals, 20 is a measuring element, and 21 to 24 are It is a connection terminal.

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

In FIG. 4, measuring terminals 11 and 12 are connected to terminal 20A of measuring element 20.
, Connect the measuring terminals 13 and 14 to the terminal 20B of the measuring element 20, supply the signal of the signal source 1 to the measuring terminal 11,
Current that connects the signal current flowing in 20 to measuring terminals 13 and 14 /
The voltage is detected by the voltage converter 8 and the inter-terminal voltage of the measuring element 20 is detected by the voltage detector 9 connected to the measuring terminals 12 and 13.

A measurement jig or the like is used for the connection between the measurement terminals 11 to 14 and the measurement element 20, and the connection is made with a cable or the like.

In FIG. 4, the connection terminals from the measurement terminals 11 to 14 to the measurement element 20 are 21 to 24.

If the connection is correct, connect the measurement terminal 11 and the connection terminal.
21, measuring terminal 12 and connection terminal 22 have the same potential,
It is connected to the terminal 20A of the measuring element 20. In addition, the measuring terminal 13
The connection terminal 23, the measurement terminal 14, and the connection terminal 24 have the same potential, and are connected to the terminal 20B of the measurement element 20.

However, due to the disconnection of the cable or poor contact, the connection terminal
21 to 24 may not be securely connected to the measuring element 20,
Correct measurement may not be possible.

For example, when the disconnection is only between the measurement terminal 11 and the connection terminal 21, the measurement signal is not supplied to the measurement element 20, the voltage between both terminals of the measurement element 20 is detected as 0V, the measurement element
The signal current flowing through 20 is detected as 0A and is measured as the impedance is indefinite.

If only the measurement terminal 14 and the connection terminal 24 are broken, the feedback path of the operational amplifier 8A is broken, and the terminal 20B of the measurement element 20 cannot be maintained at the virtual ground potential.

In this state, since the input impedance of the measuring device 13 on the measuring device side has a certain value, a minute current flows from the connecting terminal 23 to the measuring terminal 13, and the terminal voltage of the measuring element 20 shows a certain finite value. Since 14 is open, reference resistance 8B
The feedback current stops flowing through and the signal current is detected as 0A.

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

Furthermore, when only the measurement terminal 12 and the connection terminal 22 are disconnected, the measurement terminal 12 is in an open state, the inter-terminal voltage of the measurement element 20 is detected as 0 V, and the signal current flowing through the measurement element 20 is a finite value. The impedance is measured as 0Ω and the impedance is measured as 0Ω.

If only the measurement terminal 13 and the connection terminal 23 are disconnected, the feedback path of the operational amplifier 8A is disconnected and the operational amplifier 8A
A finite signal current determined by the signal generated by the reference resistance
8B, the voltage of the measuring terminal 12 becomes a value determined by this signal current.

Therefore, in this case, the measured impedance has a certain value, but does not match the impedance of the measuring element 20.

These are abnormal connection states that occur independently of each other, but they may occur in combination.

(C) Object of the Invention According to the present invention, for the measurement terminal 11 and the connection terminal 21, and the measurement terminal 12 and the connection terminal 22 connected to the terminal 20A of the measurement element 20, the switches provided between the measurement terminals 11 and 12 are opened. The continuity test and the impedance of the connection path are measured at time and when short-circuited, and then the measurement terminal 13 and the connection terminal 23, which are connected to the terminal 20B of the measurement element 20, the connection terminal 24 and the measurement terminal 14, the measurement terminal The continuity test and the impedance of the connection path are measured when the switch provided between 13 and 14 is opened and when the switch is short-circuited, and the connection is correct based on the continuity test result and the measured value of the impedance of the connection path. It is an object of the present invention to provide a terminal connection state detection circuit of a circuit element measuring device for determining whether or not.

(D) Embodiment of the Invention Next, FIG. 1 shows a configuration diagram of an embodiment according to the present invention.

Switches 3 to 7 in FIG. 1 are the same as those in FIG. 4 in other parts.

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 measuring terminal 11,
The terminal 3B is connected to the measuring terminal 13.

The switch 4 is provided between the measuring terminals 11 and 12,
The switch 5 is provided between the measuring terminals 13 and 14.

The switch 6 is connected to one end of the reference resistor 8B. The terminal 6A of the switch 6 is connected to the terminal 14, and the terminal 6B is connected to the measuring terminal 12.

The switch 7 is connected to the input terminal of the operational amplifier 8A. The terminal 7A of the switch 7 is connected to the measurement terminal 13, and the terminal 7B is connected to one end of the reference resistor 8B that constitutes the feedback circuit of the operational amplifier 8A.

The terminal connection of the switches 3 to 7 in FIG. 1 shows the state in the case of normal measurement.

Next, with reference to FIG. 2, a case of conducting a continuity test between the measuring terminals 11 and 12 will be described.

 The switches 3 to 7 are set to the positions shown in FIG.

If the connection terminal 21 and the connection terminal 22 are correctly connected at the terminal 20A of the measuring element 20, the measurement signal current i ₁ is from the terminal 3A of the switch 3 to the measurement terminal 11 → the connection terminal 21 → the connection terminal 22.
→ Measurement terminal 12 → Flows in the path of terminal 6B of switch 6.

The reference resistor 8B is connected to the operational amplifier 8A as a feedback resistor of the operational amplifier 8A by the switch 7, and the terminal 6B of the switch 6, that is, the measurement terminal 12 becomes a virtual ground potential,
The voltage E _i1 appears at the output of the differential amplifier 8C. This voltage E _i1
, If the sum of connection impedance of the connection to the impedance of such a cable terminal 21 and 22 and Z _H, the formula (1).

−E _i1 = {Rr / (Rs + Z _H )} × Es (1) where Rr is the resistance value of the reference resistor 8B, Rs is the resistance value of the resistor 2, and Es is the voltage of the signal source 1.

When formula (1) is expanded and rewritten as a formula for obtaining Z _H , formula (2) is obtained.

_{Z H = (E S / -E} i1) × Rr-Rs ...... (2) Next, the short-circuiting switch 4.

The signal current i _1s flowing at this time is irrespective of the connection path of the measurement terminal 11 → the connection terminal 21 → the connection terminal 22 → the measurement terminal 12,
Since the measuring terminals 11 and 12 are short-circuited by the switch 4, the terminal 3A of the switch 3 passes through the switch 4, and the terminal of the switch 6
The signal voltage of E _i1s is detected at the output of the differential amplifier 8C. E _{i1s at} this time is represented by Expression (3).

−E _i1s = (Rr / Rs) × Es (3) Expanding equation (3) and rewriting it to obtain Rs _yields equation (4).

Rs = (Es / −E _i1s ) × Rr (4) Substituting equation (4) into equation (2) yields equation (5).

Z _H = {(1 / −E _i1 ) − (1 / −E _i1s )} × Es × Rr (5) If Es of the reference resistor 8B and the signal source 1 is a known value, switch 4 is opened. Z _H can be easily calculated from the value of the detected voltage E _i1 at that time and the value of the detected voltage E _i1s when the switch 4 is short-circuited.

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

 The switches 3 to 7 are set to the positions shown in FIG.

When the connection terminal 23 and the connection terminal 24 are correctly connected to the terminal 20B of the measuring element 20, the current i ₂ is from the terminal 3B of the switch 3 to the measurement terminal 13 → the connection terminal 23 → the connection terminal 24 → the measurement terminal 14 → It flows through the connection path of terminal 6A 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 a switch 6 is provided.
6A, that is, the connection terminal 14 becomes a virtual ground potential, and a differential amplifier for detecting the terminal voltage of the reference resistor 8B.
The signal voltage of E _i2 is output to the output of 8C. This voltage E
_i2 is the impedance of the measurement cable and the connection terminal 23
・ If the total impedance of the 24 connection impedances is Z _L , it is expressed by equation (6).

−E _i2 = {Rr / (Rs + Z _L )} × E s (6) Expanding equation (6) and rewriting it to obtain Z _L yields equation (7).

Z _L = (Es / −E _i2 ) × Rr−Rs (7) Next, the switch 5 is short-circuited.

The signal current i _2S flowing at this time is irrespective of the connection path of the measurement terminal 13 → the connection terminal 23 → the connection terminal 24 → the measurement terminal 14,
Since the measuring terminals 13 and 14 are short-circuited by the switch 5, the terminal 3B of the switch 3 passes through the switch 5 and the terminal of the switch 6
The signal voltage of E _i2s is detected at the output of the differential amplifier 8C by flowing in the path of 6A.

E _{i2s at} this time is represented by Expression (8).

-E _i2s = (Rr / Rs) x Es (8) Expanding equation (8) and rewriting it to obtain Rs _yields equation (9).

R _s = (E _S / −E _i2s ) × R _r (9) Substituting equation (9) into equation (7) yields equation (10).

Z _L = {(1 / −E _i2 ) − (1 / −E _i2s )} × Es × Rr (10) If the reference resistance 8B and Es of the signal source 1 are known values, the switch 5 is opened. Z _L can be easily calculated from the detected voltage E _i2 at this time and the value of the detected voltage E _i2s when the switch 5 is short-circuited.

If the cable path breaks or the contact resistance increases and the connection path impedance increases at the connection point with the measuring element 20, the detected E _i1 or E _i2 voltage is connected normally. The value will be lower than the case. This is easily understood from the equations (1) and (6).

By comparing Z _H and Z _L measured in the continuity test of FIGS. 2 and 3 with a reference value for determination at the time of correct connection in advance, it is possible to determine whether or not they are correctly connected.

When properly connected, set switches 3 to 7 to the first
At the position shown in the figure, measurement of the measuring element 20 is started.

As a simple continuity test method, voltage E
If s, resistance Rs, and resistance Rr are known values, switches 4 and 5
The continuity test can be performed without providing.

E _is calculated in advance by equation (3) or equation (8), and E _is measured by connecting as shown in FIG.
_It may be determined by comparing _i1 and E _is . Further, it may be determined by comparing E _i2 and E _is measured by connecting as shown in FIG.

By providing the switches 3 to 7, the voltage between the measurement terminals 11 and 12 and between the measurement terminals 13 and 14 is detected by the continuity test, the impedance of the connection path is obtained from the flowing current and the voltage between the terminals, and the connection is correctly established. If it is determined that the connection is abnormal, a connection error can be displayed on the display unit or the like equipped in the device, and the impedance of the connection path between Z _H and Z _L can be displayed as a measured value.

(E) Effect of the Invention According to the present invention, since the continuity test for confirming the connection state between each measurement terminal and the measurement element can be performed by setting the switch, the electrical connection can be confirmed. It is possible to prevent a measurement error due to an abnormal connection.

Further, since the connection path impedance between the measurement terminal and the connection terminal can be measured, the impedance of the connection path can be notified.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment according to the present invention, FIG. 2 is a connection diagram when conducting a continuity test between measuring terminals 11 and 12, and FIG. 3 is a conducting test between measuring terminals 13 and 14. Connection diagram,
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 / voltage converter, 8A …… operational amplifier, 8B …… reference resistance, 8C …… differential amplifier, 9 …… voltage detector, 11 to 14 ……
Measuring terminal, 20 …… Measuring element, 21-24 …… Connection terminal.

Claims (1)

[Claims] 1. A first measuring terminal (11) and a second measuring terminal (12) are connected to a first terminal (20A) of a measuring element (20),
Connect the third measuring terminal (13) and the fourth measuring terminal (14) to the second terminal (20B) of the measuring element (20) to obtain the signal source (1)
Signal to the first measuring terminal (11) and the measuring element (2
The signal current flowing in 0) is detected by the current / voltage converter (8) connected to the third measuring terminal (13) and the fourth measuring terminal (14), and the voltage between the terminals of the measuring element (20) is detected. In a circuit element measuring device for detecting with a voltage detector (9) connected to the second measuring terminal (12) and the third measuring terminal (13), a first measuring terminal (11) and a second measuring terminal ( A first switch (4) for short-circuiting and opening between 12) and a second switch (5) for short-circuiting and opening between the third measuring terminal (13) and the fourth measuring terminal (14) When conducting a continuity test between the first measurement terminal (11) and the second measurement terminal (12), connect the signal of the signal source (1) to the first measurement terminal (11), The second measuring terminal (12) is connected to the current / voltage converter (8), the first switch (4) is short-circuited and opened, and the third measuring terminal (13) and the fourth measuring terminal (14) When conducting a continuity test between the two, connect the signal from the signal source (1) to the third measuring terminal (13) and connect the fourth measuring terminal (14) to the current / voltage converter (8). , A terminal state detection circuit for a circuit element measuring device, characterized in that the second switch (5) is short-circuited and opened.