A four-wire measurement system

Abstract

The utility model discloses a four -wire measurement system, include: voltage source, current source 1 and its equivalent internal resistance R3, current source 2 and its equivalent internal resistance R4, ammeter, voltmeter, switch K1, K2, K3, K4, voltage sampling module U1, U2, equivalent contact impedance R1, R2. The four -wire measurement system of the utility model, its can adopt the method of constant -current source detection four -wire terminal and output terminal between voltage drop, through exerting a little constant current, this current will not cause damage to the measured device, can reuse ohm law and calculate actual contact resistance.

Description

Technical Field

[0001] This utility model relates to a four-wire measurement system. Background Technology

[0002] Four-wire measurement is a common method in many measurement applications. However, poor contact can easily occur when changing test products, which can be fatal to sensitive components. In such cases, performing a safety connection test before measurement to ensure a low-resistance electrical contact between the fixture, probe, connector, and DUT is very helpful.

[0003] More specifically, the existing circuit diagram for four-wire measurement is as follows: Figure 1 As shown, when K1 and K2 are tangent to HI and LO respectively, it is a two-wire measurement; when K1 and K2 are tangent to SH and SL respectively, it is a four-wire measurement. In this case, the voltage drop caused by the output wires and contact impedance, i.e., the voltage drop across R1 and R2, can be eliminated. However, when insufficient contact or incorrect wiring occurs, the measurement may damage the DUT. If the equivalent resistance R1 and R2 are measured in advance, and the fault is eliminated in advance, the measurement can be made safer. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this utility model provides a four-wire measurement system, comprising: a voltage source, a current source 1 and its equivalent internal resistance R3, a current source 2 and its equivalent internal resistance R4, an ammeter, a voltmeter, switches K1, K2, K3, and K4, voltage sampling modules U1 and U2, and equivalent contact impedances R1 and R2. One end of R1 is connected to one end of R2 via an ammeter and a voltage source. A pair of input terminals of U1 are connected to both ends of R1 respectively. Current source 1, R3, and K3 are also connected between the two ends of R1. A voltmeter is also connected between the two ends of R1 via K1. A pair of input terminals of U2 are connected to both ends of R2 respectively. Current source 2, R4, and K4 are also connected between the two ends of R2. A voltmeter is also connected between the two ends of R2 via K2. The output terminals of U1 and U2 are connected to the voltmeter respectively.

[0005] Preferably, the switch K1 is model ADG1209.

[0006] Preferably, the switch K2 is model ADG1209.

[0007] Preferably, the voltage sampling module U1 is model LTC2051HV.

[0008] Preferably, the voltage sampling module U2 is model LTC2051HV.

[0009] The advantages and beneficial effects of this utility model are as follows: It provides a four-wire measurement system that can use a constant current source to detect the voltage drop between the four-wire terminals and the output terminals. By applying a very small constant current, this current will not damage the device being measured, and the actual contact resistance can be calculated using Ohm's law.

[0010] The four-wire measurement system of this utility model adds some lines to the existing four-wire measurement system. The principle and features of the four-wire measurement system of this utility model include: 1. Add a current source module, with R3 and R4 being its equivalent internal resistances, to ensure that the current flowing through R1 and R2 will not be too large during measurement.

[0011] 2. R1 and R2 are equivalent contact impedances, and U1 and U2 are voltage sampling modules.

[0012] 3. When performing a standard four-wire measurement, K3 and K4 are disconnected; when K1 and K2 are tangent to HI and LO respectively, it is a two-wire measurement; when K1 and K2 are tangent to SH and SL respectively, it is a four-wire measurement. At this time, the voltage drop caused by the output wire and contact impedance can be eliminated, that is, the voltage drop across R1 and R2.

[0013] 4. When performing a safety connection test, the voltage source outputs 0V; when K3 is closed, current source 1, R1, K3, and R3 form a circuit, and U1 samples the voltage across R1 and transmits it back to the voltmeter; when K4 is closed, current source 2, R2, K3, and R4 form a circuit, and U2 samples the voltage across R2 and transmits it back to the voltmeter.

[0014] 5. Given that the current of current source 1 is IH and the current of current source 2 is IL; the voltage read back by U1 is VH and the voltage read back by U2 is VL; we can obtain R1=VH / IH and R2=VL / IL.

[0015] 6. You can set the upper limit values ​​for R1 and R2. An error will be reported if the upper limit is exceeded.

[0016] 7. Shares a voltmeter with four-wire measurement, saving circuit costs. Attached Figure Description

[0017] Figure 1 This is the circuit diagram for an existing four-wire measurement system; Figure 2 This is the circuit diagram of the four-wire measurement system of this utility model. Detailed Implementation

[0018] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solution of this utility model and should not be construed as limiting the scope of protection of this utility model.

[0019] The specific technical solution of this utility model is as follows: like Figure 2 As shown, this utility model provides a four-wire measurement system, including: a voltage source, a current source 1 and its equivalent internal resistance R3, a current source 2 and its equivalent internal resistance R4, an ammeter, a voltmeter, switches K1, K2, K3, and K4, voltage sampling modules U1 and U2, and equivalent contact impedances R1 and R2. The model number of switch K1 is ADG1209; the model number of switch K2 is ADG1209; the model number of voltage sampling module U1 is LTC2051HV; the model number of voltage sampling module U2 is LTC2051HV. One end of R1 is connected to one end of R2 via an ammeter and a voltage source. A pair of input terminals of U1 are connected to both ends of R1 respectively. Current source 1, R3, and K3 are also connected between the two ends of R1. A voltmeter is also connected between the two ends of R1 via K1. A pair of input terminals of U2 are connected to both ends of R2 respectively. Current source 2, R4, and K4 are also connected between the two ends of R2. A voltmeter is also connected between the two ends of R2 via K2. The output terminals of U1 and U2 are connected to the voltmeter respectively.

[0020] The four-wire measurement system of this utility model adds some lines to the existing four-wire measurement system. The principle and features of the four-wire measurement system of this utility model include: 1. Add a current source module, with R3 and R4 being its equivalent internal resistances, to ensure that the current flowing through R1 and R2 will not be too large during measurement.

[0021] 2. R1 and R2 are equivalent contact impedances, and U1 and U2 are voltage sampling modules.

[0022] 3. When performing a standard four-wire measurement, K3 and K4 are disconnected; when K1 and K2 are tangent to HI and LO respectively, it is a two-wire measurement; when K1 and K2 are tangent to SH and SL respectively, it is a four-wire measurement. At this time, the voltage drop caused by the output wire and contact impedance can be eliminated, that is, the voltage drop across R1 and R2.

[0023] 4. When performing a safety connection test, the voltage source outputs 0V; when K3 is closed, current source 1, R1, K3, and R3 form a circuit, and U1 samples the voltage across R1 and transmits it back to the voltmeter; when K4 is closed, current source 2, R2, K3, and R4 form a circuit, and U2 samples the voltage across R2 and transmits it back to the voltmeter.

[0024] 5. Given that the current of current source 1 is IH and the current of current source 2 is IL; the voltage read back by U1 is VH and the voltage read back by U2 is VL; we can obtain R1=VH / IH and R2=VL / IL.

[0025] 6. You can set the upper limit values ​​for R1 and R2. An error will be reported if the upper limit is exceeded.

[0026] 7. Shares a voltmeter with four-wire measurement, saving circuit costs.

[0027] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A four-wire measurement system, characterized in that, include: Voltage source, current source 1 and its equivalent internal resistance R3, current source 2 and its equivalent internal resistance R4, ammeter, voltmeter, switches K1, K2, K3, K4, voltage sampling modules U1, U2, equivalent contact impedances R1, R2; One end of R1 is connected to one end of R2 via an ammeter and a voltage source. A pair of input terminals of U1 are connected to both ends of R1 respectively. Current source 1, R3, and K3 are also connected between the two ends of R1. A voltmeter is also connected between the two ends of R1 via K1. A pair of input terminals of U2 are connected to both ends of R2 respectively. Current source 2, R4, and K4 are also connected between the two ends of R2. A voltmeter is also connected between the two ends of R2 via K2. The output terminals of U1 and U2 are connected to the voltmeter respectively.

2. The four-wire measurement system according to claim 1, characterized in that, The switch K1 is model ADG1209.

3. The four-wire measurement system according to claim 1, characterized in that, The switch K2 is model ADG1209.

4. The four-wire measurement system according to claim 1, characterized in that, The voltage sampling module U1 is model LTC2051HV.

5. The four-wire measurement system according to claim 1, characterized in that, The voltage sampling module U2 is model LTC2051HV.

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