Impedance measuring device

Abstract

The present invention discloses an impedance measuring device, comprising: a first probe, a second probe, a third probe and a fourth probe, all of which are used to connect to a piece to be detected; the first probe and the third probe are respectively used to connect to the two ends of the piece to be detected, a first power supply and a first sampling load are arranged on the loop where the first probe and the third probe are located, and current measuring devices are arranged at both ends of the first sampling load; the second probe and the fourth probe are respectively used to connect to the two ends of the piece to be detected, a first voltage measuring device is arranged on the loop where the second probe and the fourth probe are located; a first switch and a second switch, the first switch is used to control the first probe to be powered on or off, and the second switch is used to control the third probe to be powered on or off; a second power supply, a diode, and a second sampling load are connected in series and connected in parallel with the first voltage measuring device, and a second voltage measuring device is also arranged at the second sampling load. The device in the present invention can detect abnormal situations and improve the accuracy of the impedance detection results.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit performance detection, and in particular to an impedance measuring device. Background Art

[0002] Kelvin Four-terminal sensing, also known as 4T sensing, 4-wire sensing or 4-point probe method, is an electrical impedance measurement technique that uses separate electrodes for current and voltage detection, which can make more accurate measurements than traditional two-terminal (2T) sensing. Kelvin Four-wire Sensing is used in some ohmmeters and impedance analyzers, and in the wiring configuration of precision strain gauges and resistance thermometers. It can also be used to measure the sheet resistance of thin films. The key advantage of four-wire sensing is the separation of current and voltage electrodes, which eliminates the impedance of wiring and contact resistance. However, although in theory, the use of Kelvin Four-wire Sensing can measure more accurate impedance data, in actual application, there are still some situations that cause test abnormalities and large errors in the measured impedance data, such as the probe is pierced off, or the object being measured is oxidized and the probe is pierced at the oxidation position. Therefore, before the probe is connected to the object to be measured and the formal impedance detection begins, it should be determined whether the connection between the probe and the object to be measured is abnormal and whether the detection circuit between the probes is abnormal. Summary of the invention

[0003] The present invention provides an impedance measurement device for solving the problem that when using Kelvin four-wire detection to perform impedance measurement, the measurement result may have a large error due to some abnormal situations.

[0004] To this end, the present invention provides an impedance measuring device, comprising:

[0005] The first probe, the second probe, the third probe and the fourth probe are all used to connect to the part to be detected; the first probe and the third probe are respectively used to connect to two ends of the part to be detected, a first power supply and a first sampling load are provided on the loop where the first probe and the third probe are located, and current measuring devices are provided at both ends of the first sampling load; the second probe and the fourth probe are respectively used to connect to two ends of the part to be detected, and a first voltage measuring device is provided on the loop where the second probe and the fourth probe are located;

[0006] a first switch and a second switch, the first switch is used to control the first probe to be powered on or off, and the second switch is used to control the third probe to be powered on or off;

[0007] The second power supply, the diode, and the second sampling load are connected in series and in parallel with the first voltage meter. A second voltage meter is also provided at the second sampling load. The second voltage meter is used to measure the voltage across the second sampling load under the voltage of the second power supply when the first switch and the second switch are disconnected. When the first switch and the second switch are closed, the voltage applied by the first power supply to the cathode of the diode is greater than the voltage applied by the second power supply to the anode of the diode, and the second sampling load is not energized.

[0008] Furthermore, the impedance measuring device further includes: a third switch and a fourth switch, the third switch is used to control the second probe to be powered on or off, and the fourth switch is used to control the fourth probe to be powered on or off.

[0009] Furthermore, the impedance measuring device further includes: a fifth switch, used to control the second sampling load to be powered on or off from the second power supply.

[0010] Furthermore, the first power source is a voltage-controlled constant current source.

[0011] Furthermore, the impedance measuring device also includes: a third voltage measuring device, which is used to measure the voltage across the reference resistor in the voltage-controlled constant current source.

[0012] Furthermore, the first voltage measurer and the second voltage measurer are both operational amplifiers.

[0013] The technical solution provided by the present invention has the following advantages:

[0014] 1. The impedance measuring device provided by the present invention is based on a basic Kelvin four-wire detection circuit (a first probe, a second probe, a third probe, a fourth probe, a first power supply, a first sampling load, a current measuring device, and a first voltage measuring device) capable of performing impedance detection on a piece to be detected. A first switch for controlling the power on or off of the first probe and a second switch for controlling the power on or off of the second probe are provided, so that after the first probe, the second probe, the third probe, and the fourth probe are connected to the piece to be detected, only the circuit where the second probe and the fourth probe are located can be powered on by disconnecting the first switch and the second switch, so as to detect the impedance between the second probe and the fourth probe and the piece to be detected. The invention provides a basis for judging whether the connection between the two probes is abnormal; and then by setting a second power supply, a diode, a second sampling load connected in series in parallel with the first voltage measuring device, and a second voltage measuring device set at the second sampling load, the voltage across the second sampling load under the voltage of the second power supply is measured when the first switch and the second switch are disconnected, so that the resistance value of the entire circuit (the circuit where the second sampling load is located, that is, the circuit where the second probe and the fourth probe are located) can be inferred from the voltage (the resistance value of the second sampling load is known), and then the resistance value of the entire circuit is used as a basis to judge whether the circuit is abnormal, thereby preventing a large error in the impedance measurement result of the device under test due to the abnormality.

[0015] 2. The impedance measurement device provided by the present invention is provided with a third switch for controlling the second probe to be powered on or off, and a fourth switch for controlling the fourth probe to be powered on or off, so that after the first probe, the second probe, the third probe and the fourth probe are connected to the part to be detected, only the circuit where the first probe and the third probe are located can be powered on by disconnecting the third switch and the fourth switch, thereby providing a basis for determining whether the connection between the first probe and the third probe and the part to be detected is abnormal; and since the first power supply and the first sampling load are provided on the circuit where the first probe and the third probe are located, it is possible to directly determine whether the circuit where the first probe and the third probe are located is abnormal based on the current flowing through the first sampling load, thereby preventing a large error in the impedance measurement result of the part to be detected due to the abnormality. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 A schematic diagram of the circuit structure of an impedance measuring device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be internal communication between two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0020] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] This embodiment provides an impedance measurement device, such as Figure 1 As shown, the device includes: a first probe PROBE_A, a second probe PROBE_B, a third probe PROBE_C, a fourth probe PROBE_D, a first power supply, a first sampling load Rs, a current measurer U2, a first voltage measurer U3, a first switch PRY1, a second switch PRY3, a second power supply, a diode D1, a second sampling load R1 and a second voltage measurer U4.

[0022] In this embodiment, if Figure 1 As shown, the first probe PROBE_A, the second probe PROBE_B, the third probe PROBE_C, and the fourth probe PROBE_D are all used to connect to the part to be detected RL, and the first probe PROBE_A and the third probe PROBE_C are respectively used to connect to the two ends of the part to be detected RL, and the first power supply and the first sampling load Rs are provided on the loop where the first probe PROBE_A and the third probe PROBE_C are located, and the two ends of the first sampling load Rs are provided with a current measuring device U2; the second probe PROBE_B and the fourth probe PROBE_D are respectively used to connect to the two ends of the part to be detected RL, and the first voltage measuring device U3 is provided on the loop where the second probe PROBE_B and the fourth probe PROBE_D are located. In this embodiment, when the first probe PROBE_A, the second probe PROBE_B, the third probe PROBE_C, and the fourth probe PROBE_D are all connected to the part to be detected RL and powered on, the impedance of the part to be detected RL can be obtained by obtaining the current and voltage measured by the current measuring device U2 and the first voltage measuring device U3.

[0023] Specifically, Figure 1 As shown, the first power supply can be set as a voltage-controlled constant current source. Specifically, the voltage-controlled constant current source includes an operational amplifier U1, a transistor Q1, a triode Q2, a diode D2 and a reference resistor Rd. The connection relationship between the operational amplifier U1, the transistor Q1, the triode Q2, the diode D2 and the reference resistor Rd can be obtained from Figure 1 The voltage-controlled constant current source belongs to the existing design in this field, so its specific structure will not be described again. Figure 1 As shown, the voltage-controlled constant current source may also include three resistors (R3, R4 and R5) connected to the operational amplifier U1 and a reference voltage source Z1. The specific connection relationship between the three resistors and the diode is also not described in detail.

[0024] Specifically, Figure 1As shown, the current measuring device U2 can be set as a current sensor INA168NA, and the first voltage measuring device U3 can be set as an operational amplifier INA115BU to collect and amplify the voltage across the point to be detected.

[0025] In this embodiment, Figure 1 As shown, the first switch PRY1 is used to control the first probe PROBE_A to be powered on or off, and the second switch PRY3 is used to control the third probe PROBE_C to be powered on or off.

[0026] In this embodiment, Figure 1 As shown, the second power supply, the diode D1 and the second sampling load R1 are connected in series and then connected in parallel with the first voltage measuring device U3. A second voltage measuring device U4 is also provided at the second sampling load R1, and the second voltage measuring device U4 is used to measure the voltage across the second sampling load R1 under the voltage of the second power supply when the first switch PRY1 and the second switch PRY3 are disconnected. In the present application, the second power supply can be a constant voltage DC power supply, Figure 1 In the figure, a 3V DC power supply is used for illustration.

[0027] In the present application, when the first switch PRY1 and the second switch PRY3 are closed (that is, when the formal impedance measurement of the detection component RL is performed), the voltage applied by the first power supply to the cathode of the diode D1 is greater than the voltage applied by the second power supply to the anode of the diode D1, and the second sampling load R1 is not energized, that is, the second power supply and the second sampling load R1 will not affect the formal impedance measurement of the detection component RL.

[0028] In this application, in order to further prevent the second sampling load R1 from affecting the formal impedance measurement of the to-be-detected component RL, as shown in FIG. Figure 1 As shown, the impedance measuring device in this embodiment may further include a fifth switch PRY5, and the fifth switch PRY5 is used to control the second sampling load R1 to be powered on or off with the second power supply.

[0029] In this application, if Figure 1 As shown, the impedance measuring device in the present application may further include a third voltage measuring device U5, which is used to measure the voltage across the reference resistor Rd in the voltage-controlled constant current source; and based on the fact that when the voltage-controlled constant current source is normal, the voltage across the reference resistor Rd should be V_IREF, therefore, the voltage value measured by the third voltage measuring device U5 can be used to compare with the reference voltage V_IREF, so as to determine whether the voltage-controlled constant current source is abnormal.

[0030] The impedance measuring device in this embodiment is based on a basic Kelvin four-wire detection circuit (a first probe PROBE_A, a second probe PROBE_B, a third probe PROBE_C, a fourth probe PROBE_D, a first power supply, a first sampling load Rs, a current measurer U2, and a first voltage measurer U3) capable of performing impedance detection on the detected component RL. A first switch PRY1 for controlling the first probe PROBE_A to be powered on or off, and a second switch PRY3 for controlling the third probe PROBE_C to be powered on or off are provided. After the first probe PROBE_A, the second probe PROBE_B, the third probe PROBE_C, and the fourth probe PROBE_D are connected to the detected component RL, the first switch PRY1 and the second switch PRY3 can be disconnected to realize that only the circuit where the second probe PROBE_B and the fourth probe PROBE_D are located is powered on, so as to detect the impedance of PROBE_B. The fourth probe PROBE_D and the connection between the device to be tested RL are abnormal, which provides a basis for judging whether the connection between the fourth probe PROBE_D and the device to be tested RL is abnormal; and then by setting a second power supply, a diode D1, a second sampling load R1, which are connected in series and in parallel with the first voltage measuring device U3, and a second voltage measuring device U4 set at the second sampling load R1, when the first switch PRY1 and the second switch PRY3 are disconnected, the voltage across the second sampling load R1 is measured under the voltage of the second power supply, so that the resistance value of the entire circuit (the circuit where the second sampling load R1 is located, that is, the circuit where the second probe PROBE_B and the fourth probe PROBE_D are located) can be inferred from the voltage (the resistance value of the second sampling load R1 is known), and then the resistance value of the entire circuit is used as a basis to judge whether the circuit is abnormal, thereby preventing a large error in the impedance measurement result of the device to be tested due to the abnormality.

[0031] As an optional implementation, Figure 1As shown, the impedance measuring device in this embodiment may further include a third switch PRY2 and a fourth switch PRY4, wherein the third switch PRY2 is used to control the second probe PROBE_B to be powered on or off, and the fourth switch PRY4 is used to control the fourth probe PROBE_D to be powered on or off, so that after the first probe PROBE_A, the second probe PROBE_B, the third probe PROBE_C and the fourth probe PROBE_D are connected to the part to be detected RL, the third switch PRY2 and the fourth switch PRY4 can be disconnected to realize that only the circuit where the first probe PROBE_A and the third probe PROBE_C are located is powered on, providing a basis for determining whether the connection between the first probe PROBE_A and the third probe PROBE_C and the part to be detected RL is abnormal; and since the first power supply and the first sampling load Rs are provided on the circuit where the first probe PROBE_A and the third probe PROBE_C are located, therefore, at this time, it is possible to directly determine whether the circuit where the first probe PROBE_A and the third probe PROBE_C are located is abnormal based on the current flowing through the first sampling load Rs, thereby preventing a large error in the impedance measurement result of the part to be detected due to the abnormality.

[0032] The measurement process of the impedance measurement device in this embodiment is described below:

[0033] 1. The first probe PROBE_A, the second probe PROBE_B, the third probe PROBE_C and the fourth probe PROBE_D are all used to connect to the detected part RL, and the first probe PROBE_A and the third probe PROBE_C are correspondingly connected to the two ends of the detected part RL, and the second probe PROBE_B and the fourth probe PROBE_D are correspondingly connected to the two ends of the detected part RL.

[0034] 2. The first switch PRY1 and the second switch PRY3 are disconnected, and the third switch PRY2, the fourth switch PRY4 and the fifth switch PRY5 are closed. At this time, the voltage in the circuit is provided by the 3V of the positive electrode of the diode D1; the voltage Vs across the second sampling load R1 is obtained by the second voltage measuring device U4, and the resistance value in the entire loop is inferred. When the resistance value is within a predetermined range, it is determined that the detection loop (the loop where the second sampling load R1 is located, that is, the loop between the second probe PROBE_B and the fourth probe PROBE_D) is normal; otherwise, the detection loop is determined to be abnormal, and an abnormal detection report is issued.

[0035] 3. Close the first switch PRY1 and the second switch PRY3, and open the third switch PRY2, the fourth switch PRY4 and the fifth switch PRY5; at this time, the voltage at the cathode of the diode D1 is much higher than 3V, and the diode is cut off. The loop formed at this time is the drive loop between the first probe PROBE_A and the third probe PROBE_C. The current I in the loop is measured by the current measuring device U2, or the current I in the loop is obtained by the reference voltage V_IREF across the reference resistor Rd (if the voltage value across the reference resistor Rd measured by the third voltage measuring device U5 is not V_IREF, it means that the voltage-controlled constant current source is abnormal) and the resistance value of the reference resistor Rd. When the current I does not exceed the error range, the drive loop is considered normal; otherwise, the drive loop is considered abnormal and an abnormality detection report is issued.

[0036] 4. When the detection circuit and the drive circuit are normal, the first switch PRY1, the second switch PRY3, the third switch PRY2 and the fourth switch PRY4 are all closed, and the fifth switch PRY5 is opened to perform impedance detection on the detected component RL.

[0037] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. An impedance measuring device, characterized in that: include: The first probe, the second probe, the third probe and the fourth probe are all used to connect to the object to be detected; the first probe and the third probe are respectively used to connect to the two ends of the object to be detected, a first power supply and a first sampling load are provided on the loop where the first probe and the third probe are located, and current measuring devices are provided at both ends of the first sampling load; the second probe and the fourth probe are respectively used to connect to the two ends of the object to be detected, and a first voltage measuring device is provided on the loop where the second probe and the fourth probe are located; a first switch and a second switch, wherein the first switch is used to control the first probe to be powered on or off, and the second switch is used to control the third probe to be powered on or off; A second power supply, a diode, and a second sampling load are connected in series and in parallel with the first voltage measurer. A second voltage measurer is also provided at the second sampling load. The second voltage measurer is used to measure the voltage across the second sampling load under the voltage of the second power supply when the first switch and the second switch are disconnected. When the first switch and the second switch are closed, the voltage applied by the first power supply to the cathode of the diode is greater than the voltage applied by the second power supply to the anode of the diode, and the second sampling load is not energized.

2. The impedance measuring device according to claim 1, characterized in that: Also includes: A third switch and a fourth switch, wherein the third switch is used to control the second probe to be powered on or off, and the fourth switch is used to control the fourth probe to be powered on or off.

3. The impedance measuring device according to claim 1 or 2, characterized in that: Also includes: A fifth switch is used to control the second sampling load to be powered on or off from the second power supply.

4. The impedance measuring device according to claim 1, characterized in that: The first power source is a voltage-controlled constant current source.

5. The impedance measuring device according to claim 4, characterized in that: Also includes: The third voltage measuring device is used to measure the voltage across the reference resistor in the voltage-controlled constant current source.

6. The impedance measuring device according to claim 1, characterized in that: The first voltage measurer and the second voltage measurer are both operational amplifiers.

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