JPH02190771A - Four-terminal measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure the voltage across a body to be measured without damaging an element for measurement by detecting conduction between 1st and 3rd contactors and 2nd and 4th contactors, and detecting whether or not there is a potential difference between specific contactors. CONSTITUTION:When the resistance between the 1st and 3rd contactors 13 and 18 decreases, a large current flows to the secondary side of a transformer 32, and consequently the potential at the contact 38 rises and the output of an inverter 39 varies from high level to low level. Similarly, when the resistance between the 2nd and 4th contactors 16 and 19 decreases, the output of an inverter 46 varies to the low level as well. Consequently, the conduction between the respective contactors is detected. Further, when there is any potential difference between at least two of the contactors 13, 16, 18, and 19 coming into contact with electrodes 12 and 15 of the body 1 to be measured, the potential at a contact point 61 rises and a transistor 62 turns on the cause variation of the output of the inverter 62 from the low level to the high level, so a high voltage developed between contactors can be detected before four-terminal contacting, and a signal source 14, a current-voltage converter 17, buffer amplifiers 21 and 22 for voltage detection, etc., are prevented from damaging.

Description

Detailed Description of the Invention "Industrial Application Field" This invention connects a signal source to a first electrode of an object to be measured through a first tangent, and connects a signal source to a second electrode of the object to be measured. A current measuring means is connected through the contact, and a third electrode is connected between the first electrode and the second electrode. The present invention relates to a four-terminal measuring device in which a voltage measuring means is connected through a fourth contact.

"Prior Art" Figure 4 shows a conventional four-terminal measuring device. A signal source 14 is connected to the first electrode 12 of the object to be measured 11 of the capacitor through the first contact 13, and a current-voltage converter 17 is connected to the second electrode 15 of the object to be measured 11 through the second contact 16. . The first electrode 12, the second electrode] 5 each have a third contact 1
8. A high input impedance voltage buffer amplifier 21,22 is connected through the fourth contact 19. Each output of the voltage buffer amplifier 21 , 22 is connected to both inputs of the differential amplifier 23 . Current-voltage converter 17, differential amplifier 2
Each output side of 3 is connected to a vector detector 24, and the vector detector 24 is connected to an arithmetic/display section 25.

An AC voltage is applied to the object to be measured 11 from the signal source 14, and the current flowing through the object to be measured 11 is converted into voltage information by the current-voltage converter 17, and then detected as complex number information by the vector detector 24. After converting the voltage across both ends into voltage information by the voltage detection differential amplifier 23, the vector detector 24 detects it as complex number information, and the re-output of the vector detector 24 is processed to obtain the capacitance value of the object to be measured 11. and janδ value.

[Problem to be Solved by the Invention] If the contact between the first contactor 13 and the second contactor 16 is insufficient, the predetermined current cannot be passed through the object to be measured 11, resulting in incorrect measured values. . Also, the third contact 18, the fourth
If the contact of the contactor 19 is insufficient, the actual object to be measured 11
Since the voltage across the terminal is not measured, the measured value will be incorrect.

When a capacitor charged to a high voltage is connected as the object to be measured 11, a large current flows through the signal source 14 and the current-voltage converter 17, and a high voltage is applied to the voltage detection buffer amplifiers 21 and 22, damaging them. There was a risk.

"Means for Solving the Problem" According to the present invention, means for detecting conduction between the first contact and the third contact is provided, and means for detecting conduction between the second contact and the fourth contact. is provided. Furthermore, means for detecting the presence or absence of a potential difference between the first contactor and the second contactor or the fourth contactor, and means for detecting the presence or absence of a potential difference between the third contactor and the second contactor or the fourth contactor. and means for detecting.

Embodiment FIG. 1 shows an embodiment of the present invention, and parts corresponding to those in FIG. 4 are given the same reference numerals. According to the present invention, a means for detecting conduction between the first contact 13 and the third contact 18 and a means for detecting conduction between the second contact 16 and the fourth contact 19 are provided. For this reason, in FIG. 1, a contact detection signal source 31 having a frequency different from the frequency of the signal '1IA14 is provided, one end of the contact detection signal #31 is grounded, and the other end is connected to the primary side of the transformer 32, 33. connected to one end of each. Both ends of the secondary side of the transformer 32 are connected to the first contact 1
3. It is connected to the third contactor 18, and both ends of the secondary side of the transformer 33 are connected to the second contactor 16 and the fourth ti contactor 19. The other end of the primary side of the transformer 32 is grounded through a resistor 34 and connected to one end of a diode 35.
The other end of the diode 35 is grounded through a capacitor 36 and a resistor 37, respectively, and a connection point 38 between the diode 35 and the microcapacitor 36 is connected to an inverter 39. The other end of the primary side of the transformer 33 is grounded through a resistor 41 and connected to one end of a diode 42, and the other end of the diode 42 is grounded through a capacitor 43 and a resistor 44, respectively. A connection point 45 is connected to an inverter 46.

means for detecting the presence or absence of a potential difference between the first contact 13 and the second contact 16 or the fourth contact 19; and a third contact 18.
and means for detecting the presence or absence of a potential difference between the second contactor 16 or the fourth contactor 19. For this reason, the first. Second. Third. The fourth contacts 13, 16, 18.19 are each connected to one end of a resistor 47, 48, 49, 51, and the other end of the resistor 47, 48, 49, 51 is connected to a zener diode 52, 53, respectively. , 54.55. The connection point between the resistor 47 and the Zener diode 52 is connected to the anode of the diode 56, the connection point between the resistor 48 and the Zener diode 53 is connected to the anode of the diode 57, and the connection point between the resistor 49 and the Zener diode 54 is connected to the anode of the diode 56. The connection point between the resistor 51 and the Zener diode 55 is connected to the anode of the diode 59. The cathodes of the diodes 56, 57, 58, 59 are connected to each other, their connection point 61 is connected to the base of the transistor 62, the emitter of the transistor 62 is grounded, and the collector is connected to the power supply terminal 64 through the resistor 63. It is also connected to an inverter 65.

The outputs of the inverters 39, 46, and 65 are supplied to a NOR circuit 66, and the output of the NOR circuit 66 is supplied to the base of a transistor 67. The collector of transistor 67 is connected to power supply terminal 64 through relays 68, 69, 71, 72, and the emitter is grounded. Contact 68a of relay 68
is inserted between the first contact 13 and the signal source 14, the contact 69a of the relay 69 is inserted between the second contact 16 and the current-voltage converter 17, and the contact 71a of the relay 71 is inserted between the third contact 13 and the signal source 14.
The contact 72 a of the relay 72 is inserted between the fourth contact 19 and the voltage buffer amplifier 22 .

Each output of the inverters 39 and 46 is also supplied to the NOR circuit 73, and the output of the NOR circuit 73, the output of the inverter 65, and the automatic command are supplied to the AND circuit 74, and the output of the AND circuit 74 is supplied to the base of the transistor 75. The collector of the transistor 75 is connected to the power supply terminal 64 through the relay 76, and the emitter is grounded. relay 76
A contact 76a is connected between the third contact 18 and the fourth contact 19.

In the above-described configuration, when the resistance between the first contact 13 and the third contact 18 decreases, a large iIt current flows to the secondary side of the transformer 32, and the primary side of the transformer 32 and the resistor 3
A large current flows through the resistor 4, which is detected by the diode 35 and flows through the resistor 37. Therefore, the potential at the connection point 38 rises, and the output of the inverter 39 changes from high level to low level.

Similarly, when the resistance between the second contact 16 and the fourth contact 19 decreases, the output of the inverter 46 changes from a high level to a low level. In this way, conduction between the first contactor 13 and the third contactor 18 and conduction between the second contactor 16 and the fourth contactor 19 are detected.

The first electrode contacts the first electrode 12 and the second electrode 15 of the object to be measured 11. Second. Third. 4th contact 13.16°18.19
endogenous at least to some extent between two contacts, for example 3■
If there is a potential difference above, the potential at the connection point 61 increases, the transistor 62 becomes conductive, and the output of the inverter 65 changes from a low level to a high level. For example, the IOV potential difference between the first contact 13 and the fourth contact 19 (first contact 13
is positive and the fourth contact 19 is negative), the current flows through the resistor 4
7 Zener diode 52 - Zener diode 55 flows through resistor 51, and among the two Zener diodes 52, 55,
A Zener voltage, for example 3.5 cm, is generated only in the Zener diode 52 in the reverse direction. This voltage across the terminal forward biases the diode 56 to raise the potential at the connection point 61. Therefore, transistor 62 becomes conductive, and the output of inverter 65 becomes high level.

Next, if voltage is applied in the opposite direction, that is, the first contact 1
3 is negative and the fourth contact 19 is positive, the current flows through the resistor 51
- Zener diode 55 - Zener diode 52 - resistor 47, and of the two Zener diodes 52 and 55, a Zener voltage is generated only in the opposite Zener diode 55, and the Zener voltage forward biases the diode 59, The potential of the connection point 61 is raised, the transistor 62 becomes conductive, and the output of the inverter 65 becomes high level. Similarly, the high voltage generated between all the contacts can be detected before the four-terminal connection is established.

There is low resistance between the first contact 13 and the third contact 18,
When the second contact 16 and the fourth contact 19 have low resistance and no high voltage is generated between the first electric scraper 12 and the second electrode 15, the outputs of the inverter 39°46°65 are both The output of the NOR circuit 66 becomes a high level, the transistor 67 becomes conductive, and the relays 68, 69,
71 and 72 operate together, the measurement signal of the signal source 14 is applied to the device under test 11, the current flowing through the device under test 11 is detected by the current-voltage converter 17, and the voltage across the device 11 is detected. is detected by the differential amplifier 23, and the capacitance of the device under test 11 is measured.

A state in which a four-terminal connection is established, that is, between the first contact 13 and the third contact 18, and between the second contact 16 and the fourth contact 19.
When the first electrode 12 and the second electrode 15
If a high voltage is generated between them, the potential at the connection point 61 increases, the output of the inverter 65 becomes high level, and the output of the NOR circuit 73 is also high level, so if an automatic command is given, the AND circuit 74 The output of the inverter 65 becomes high level, the transistor 75 is turned on, the relay 76 is operated, and the first electrode 12 and the second electrode 15 are connected through the relay contact 76a. It will automatically discharge until it reaches a low level.

Four-terminal contact detection may be configured as shown in FIG.

When the resistance between the first contact 13 and the third contact 18 becomes low, the relay 77 operates, and the contact of the relay 77? ? The input side of the logic circuit 78 is grounded by a, and the output of the logic circuit 78 becomes a low level rather than a high level. Similarly, when the resistance between the second contact 16 and the fourth contact 19 becomes low, the relay 79 is activated, its contact 79a is turned on, and the input side of the logic circuit 81 is grounded, causing the output of the logic circuit 81 to rise above the high level. It becomes low and healthy. As shown in FIG. 3, photocouplers 82 and 83 may be used in place of the relays 77 and 79.

"Effects of the Invention" As described above, according to the present invention, the contact state of each contact can be detected, and a predetermined current can be passed through the object to be measured.
It is also possible to accurately measure the voltage across the object under test.
Correct measurements can be obtained.

When a device under test charged to a high voltage is connected, the output of the inverter 65 becomes high level, and this is detected. Using this detection, it is also possible to automatically discharge the charge of the object under test, in which case there is no risk of damaging the signal source, current-voltage converter, voltage detection buffer amplifier, etc.

[Brief Description of the Drawings] Fig. 1 is a connection diagram showing an embodiment of the present invention, Figs. 2 and 3 are connection diagrams showing partial modifications thereof, and Fig. 4 is a connection diagram showing a conventional four-terminal measuring device. FIG.

Claims (1)

[Claims] (1) A signal source is connected to the first electrode of the object to be measured through the first contact, a current measuring means is connected to the second electrode of the object to be measured through the second contact, and the signal source is connected to the first electrode of the object to be measured through the second contact. In a four-terminal measuring device in which a voltage measuring means is connected between the electrodes through third and fourth contacts, means for detecting continuity between the first contact and the third contact, the second contact and the above. means for detecting continuity between the fourth contact; means for detecting the presence or absence of a potential difference between the first contact and the second contact or the fourth contact; and the third contact and the fourth contact. A four-terminal measuring device comprising means for detecting the presence or absence of a potential difference between the second contactor and the fourth contactor.