Three-wire system thermal resistance measuring system and method

Abstract

The invention relates to a three-wire system thermal resistance measurement system and method. The system comprises four groups of transient voltage suppressors, three cables, two constant current sources, a bias resistor, two switches, an output circuit, an output end of a first constant current source and a negative electrode of a first transient voltage suppressor, wherein one end of a first switch is connected with one end of a thermal resistor through a first cable; the other end of the first switch is connected with the negative electrode of the second transient voltage suppressor; the other end of the thermal resistor is grounded through a third cable; the output end of the second constant current source, the negative electrode of the third transient voltage suppressor and one end of the second switch are connected with the other end of the thermal resistor through the biasing resistor and the second cable in sequence; the other end of the second switch is connected with the negative electrode of the fourth transient voltage suppressor; and the output circuit is used for outputting the amplified voltage difference between the output ends of the first constant current source and the second constant current source. The resistance value of the thermal resistor is calculated, high EMC performance is achieved, and measurement errors caused by non-linear reverse leakage current are eliminated.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal resistors, and more particularly, relates to a three-wire thermal resistor measurement system and method. Background Art

[0002] Temperature measurement is a common detection technique in the analog field. A common method for measuring temperature is to measure the resistance of a thermistor (RTR) at different temperatures. RTDs can measure temperatures from -200°C to +800°C. 100Ω and 1000Ω platinum resistors are the most common. Using a three-wire IC circuit eliminates lead resistance errors.

[0003] CN119533693A discloses a device for improving the measurement accuracy of thermal resistors and a method for manufacturing the device. This device, which belongs to the field of power equipment technology, includes a signal line, a temperature measuring plate, a support rod, and a heat shrink tubing. The temperature measuring plate has one side as a connection surface and the other side as a detection surface. One end of the signal line faces and connects to the connection surface. The support rod extends parallel to the signal line and is connected to the connection surface. The signal line and support rod are both threaded through the heat shrink tubing, which contracts radially when heated, thereby wrapping around the signal line and support rod.

[0004] However, existing measurement methods do not take into account the harsh electromagnetic environment in which electronic devices must face higher interference levels and more complex EMC (Electromagnetic Compatibility) events, such as electrostatic discharge, electrical fast transients, radiated susceptibility, conducted susceptibility, and surges.

[0005] In existing technology, the most common EMC protection method is the use of transient voltage suppressors (TVSs). The maximum clamping voltage of a TVS determines the maximum interference signal voltage that the TVS can suppress. However, most TVS suppliers only provide typical values for device parameters, rather than calculating the leakage current error of the TVS at a specific voltage. Therefore, the nonlinear reverse leakage current corresponding to the TVS can cause significant errors in the measurement of thermal resistors. Summary of the Invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a three-wire thermal resistor measurement system and method.

[0007] The present invention adopts the following technical solutions.

[0008] The first aspect of the present invention provides a three-wire thermal resistor measurement system, comprising four sets of transient voltage suppressors, three cables, two constant current sources, a bias resistor R3, two switches, and an output circuit, characterized in that:

[0009] The output end of the first constant current source I1, the negative electrode of the first transient voltage suppressor TVS11, and one end of the first switch SSR1 are all connected to one end of the first cable; the other end of the first switch SSR1 is connected to the negative electrode of the second transient voltage suppressor TVS12; the positive electrode of the first transient voltage suppressor TVS11 and the positive electrode of the second transient voltage suppressor TVS12 are both connected to ground; the other end of the first cable is connected to one end of the thermal resistor Rt; the other end of the thermal resistor Rt is connected to ground through a third cable;

[0010] The output end of the second constant current source I2, the negative electrode of the third transient voltage suppressor TVS21, and one end of the second switch SSR2 are all connected to one end of the bias resistor R3, and the other end of the bias resistor R3 is connected to the other end of the thermal resistor Rt through a second cable; the other end of the second switch SSR2 is connected to the negative electrode of the fourth transient voltage suppressor TVS22; the positive electrode of the third transient voltage suppressor TVS21 and the positive electrode of the fourth transient voltage suppressor TVS22 are both connected to ground;

[0011] Wherein, there is internal resistance between both ends of the first, second and third cables;

[0012] The two input terminals of the output circuit are connected to the output terminals of the first and second constant current sources I1 and I2 respectively. The output circuit is used to output the amplified voltage difference between the output terminals of the first and second constant current sources I1 and I2.

[0013] Preferably, the three-wire thermal resistance measurement system further includes a first diode D1; the first diode D1 is connected between the third cable and the ground;

[0014] The other end of the third cable is connected to the anode of the first diode D1 , and the cathode of the first diode D1 is connected to the ground.

[0015] Preferably, the first switch SSR1 and the second switch SSR2 are both optical coupling relays, which are selected from the same batch and model and are composed of a diode and a light-driven chip switch; the leakage current of the optical coupling relays is equal to or less than 1nA.

[0016] Preferably, the resistance of the bias resistor R3 is equal to the resistance of the thermal resistor Rt at a temperature of -54°C.

[0017] Preferably, the output circuit is composed of an amplifier, the positive input terminal of the amplifier is connected to the output terminal of the first constant current source I1, the negative input terminal of the amplifier is connected to the output terminal of the second constant current source I2, and the output terminal of the amplifier is the output terminal of the output circuit.

[0018] Preferably, the first, second, third and fourth transient voltage suppressors TVS11, TVS12, TVS21 and TVS22 are from the same batch of transient voltage suppressors, and the reverse leakage current corresponding IV curves of the first, second, third and fourth transient voltage suppressors are the same.

[0019] Preferably, the first, second and third cables are made of the same material and length and have the same temperature coefficient, and the internal resistances r1, r2 and r3 between the two ends of the first, second and third cables are all equal.

[0020] Preferably, the currents output by the first constant current source I1 and the second constant current source I2 are equal.

[0021] A second aspect of the present invention provides a three-wire thermal resistor measurement method using the system described in the first aspect of the present invention, characterized by comprising:

[0022] Control the first switch SSR1 and the second switch SSR2 to be turned off, and obtain the voltage difference U output by the output circuit at this time AB ; Control the first switch SSR1 and the second switch SSR2 to turn on, and obtain the voltage difference U' output by the output circuit at this time AB ;

[0023] Calculate the difference between the two voltage differences and calculate the resistance R of the thermal resistor Rt according to the following formula t , the formula is:

[0024]

[0025] Wherein, I is the output current value of the first and second constant current sources, G is the amplification factor of the output circuit; R3 is the resistance value of the bias resistor R3.

[0026] The beneficial effect of the present invention is that, compared with the prior art, the present invention adopts a three-wire thermal resistor measurement system and method, sets four groups of transient voltage suppressors to generate reverse leakage current, uses the transient voltage suppressors to ensure high EMC performance, and controls the switching of two groups of transient voltage suppressors through optical coupling relays, thereby achieving controllable changes in the reverse leakage current, and the true thermal resistor resistance value can be calculated based on the voltage measurement difference before and after switching, thereby simultaneously eliminating the influence of the transient voltage suppressor TVS reverse leakage current on the temperature result, and using the same batch of low-leakage optical coupling relays and transient voltage suppressors with consistent performance, simplifying calculations and reducing errors caused by components. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0028] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. The embodiments described in this application are only part of the embodiments of the present invention, not all of them. Based on the spirit of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] like Figure 1 As shown, embodiment 1 of the present invention provides a three-wire thermal resistor measurement system, including four sets of transient voltage suppressors, three cables, two constant current sources, a bias resistor R3, two switches, and an output circuit, characterized in that:

[0030] The output end of the first constant current source I1, the negative electrode of the first transient voltage suppressor TVS11, and one end of the first switch SSR1 are all connected to one end of the first cable; the other end of the first switch SSR1 is connected to the negative electrode of the second transient voltage suppressor TVS12; the positive electrode of the first transient voltage suppressor TVS11 and the positive electrode of the second transient voltage suppressor TVS12 are both connected to ground; the other end of the first cable is connected to one end of the thermal resistor Rt; the other end of the thermal resistor Rt is connected to ground through a third cable;

[0031] The output end of the second constant current source I2, the negative electrode of the third transient voltage suppressor TVS21, and one end of the second switch SSR2 are all connected to one end of the bias resistor R3, and the other end of the bias resistor R3 is connected to the other end of the thermal resistor Rt through a second cable; the other end of the second switch SSR2 is connected to the negative electrode of the fourth transient voltage suppressor TVS22; the positive electrode of the third transient voltage suppressor TVS21 and the positive electrode of the fourth transient voltage suppressor TVS22 are both connected to ground;

[0032] Wherein, there is internal resistance between both ends of the first, second and third cables;

[0033] The two input terminals of the output circuit are connected to the output terminals of the first and second constant current sources I1 and I2 respectively. The output circuit is used to output the amplified voltage difference between the output terminals of the first and second constant current sources I1 and I2.

[0034] The three-wire thermal resistance measurement system further includes a first diode D1; the first diode D1 is connected between the third cable and the ground;

[0035] The other end of the third cable is connected to the anode of the first diode D1 , and the cathode of the first diode D1 is connected to the ground.

[0036] The first switch SSR1 and the second switch SSR2 are both optical coupling relays, which are selected from the same batch and model and are composed of a diode and a light-driven chip switch; the leakage current of the optical coupling relays is equal to or less than 1nA.

[0037] The resistance of the bias resistor R3 is equal to the resistance of the thermal resistor Rt when the temperature is -54°C.

[0038] The output circuit includes an amplifier, wherein the positive input terminal of the amplifier is connected to the output terminal of the first constant current source I1, and the negative input terminal of the amplifier is connected to the output terminal of the second constant current source I2.

[0039] The first, second, third and fourth transient voltage suppressors TVS11, TVS12, TVS21 and TVS22 are transient voltage suppressors from the same batch, and the IV curves corresponding to the reverse leakage current are the same.

[0040] The first, second and third cables are made of the same material and length and have the same temperature coefficient, and the internal resistances r1, r2 and r3 between the two ends of the first, second and third cables are all equal.

[0041] The currents output by the first constant current source I1 and the second constant current source I2 are equal.

[0042] Embodiment 2 of the present invention provides a three-wire thermal resistor measurement method using the system described in embodiment 1 of the present invention, characterized by comprising:

[0043] Control the first switch SSR1 and the second switch SSR2 to be turned off, and obtain the voltage difference U output by the output circuit at this time AB ; Control the first switch SSR1 and the second switch SSR2 to turn on, and obtain the voltage difference U' output by the output circuit at this time AB ;

[0044] The specific formula is:

[0045] U AB ={[(r1+R t +r3)·(I1-I TVS11 )+U D1 ]

[0046] -[(r2+R3+r3)·(I2-I TVS21 )+U D1 ]}·G

[0047] U′ AB ={[(r1+R t +r3)·(I1-I TVS11 -I TVS12 )+U D1 ]

[0048] -[(r2+R3+r3)·(I2-I TVS11 -I TVS22 )+U D1 ]}·G

[0049] Where G is the amplification factor of the output circuit; r1, r2, and r3 are the internal resistances between the two ends of the first, second, and third cables, respectively. TVS11 , I TVS12 , I TVS11 , I TVS22 are the reverse leakage currents of the first, second, third and fourth transient voltage suppressors respectively; R3 is the resistance value of the bias resistor R3, R t is the resistance of the thermal resistor Rt, I1 and I2 are the output currents of the first constant current source and the second constant current source respectively.

[0050] The difference between the two voltage differences is calculated, and the resistance of the thermal resistor Rt is calculated based on the difference, the resistance of the bias resistor R3, and the amplification factors of the first and second constant current source output current output circuits.

[0051] In this embodiment, the output currents of the first and second constant current sources are equal, the reverse leakage currents of the first, second, third and fourth transient voltage suppressors are equal, and the internal resistances between the two ends of the first, second and third cables are equal; in this case, the resistance value of the thermal resistor Rt is calculated as R t , the formula is:

[0052]

[0053] Wherein, I is the output current value of the first and second constant current sources.

[0054] The present disclosure may be a system, method and / or computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for causing a processor to implement various aspects of the present disclosure.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered by the scope of protection of the claims of the present invention.

Claims

1. A three-wire RTD measurement system, comprising four sets of transient voltage suppressors, three cables, two constant current sources, a bias resistor R3, two switches, and an output circuit, characterized in that: The output end of the first constant current source I1, the negative electrode of the first transient voltage suppressor TVS11, and one end of the first switch SSR1 are all connected to one end of the first cable; the other end of the first switch SSR1 is connected to the negative electrode of the second transient voltage suppressor TVS12; the positive electrode of the first transient voltage suppressor TVS11 and the positive electrode of the second transient voltage suppressor TVS12 are both connected to ground; the other end of the first cable is connected to one end of the thermal resistor Rt; the other end of the thermal resistor Rt is connected to ground through a third cable; The output end of the second constant current source I2, the negative electrode of the third transient voltage suppressor TVS21, and one end of the second switch SSR2 are all connected to one end of the bias resistor R3, and the other end of the bias resistor R3 is connected to the other end of the thermal resistor Rt through a second cable; the other end of the second switch SSR2 is connected to the negative electrode of the fourth transient voltage suppressor TVS22; the positive electrode of the third transient voltage suppressor TVS21 and the positive electrode of the fourth transient voltage suppressor TVS22 are both connected to ground; Wherein, there is internal resistance between both ends of the first, second and third cables; The two input terminals of the output circuit are connected to the output terminals of the first and second constant current sources I1 and I2 respectively. The output circuit is used to output the amplified voltage difference between the output terminals of the first and second constant current sources I1 and I2.

2. A three-wire thermal resistance measurement system according to claim 1, characterized in that: The three-wire thermal resistance measurement system further includes a first diode D1; the first diode D1 is connected between the third cable and the ground; The other end of the third cable is connected to the anode of the first diode D1 , and the cathode of the first diode D1 is connected to the ground.

3. A three-wire thermal resistance measurement system according to claim 2, characterized in that: The first switch SSR1 and the second switch SSR2 are both optical coupling relays, which are selected from the same batch and model and are composed of a diode and a light-driven chip switch; the leakage current of the optical coupling relays is equal to or less than 1nA.

4. A three-wire thermal resistance measurement system according to claim 1, characterized in that: The resistance of the bias resistor R3 is equal to the resistance of the thermal resistor Rt when the temperature is -54°C.

5. The three-wire thermal resistance measurement system according to claim 1, characterized in that: The output circuit is composed of an amplifier, the positive input terminal of the amplifier is connected to the output terminal of the first constant current source I1, the negative input terminal of the amplifier is connected to the output terminal of the second constant current source I2, and the output terminal of the amplifier is the output terminal of the output circuit.

6. A three-wire thermal resistance measurement system according to claim 1, characterized in that: The first, second, third and fourth transient voltage suppressors TVS11, TVS12, TVS21 and TVS22 are transient voltage suppressors from the same batch, and the reverse leakage current corresponding IV curves of the first, second, third and fourth transient voltage suppressors are the same.

7. A three-wire thermal resistance measurement system according to claim 6, characterized in that: The first, second and third cables are made of the same material, have the same length and have the same temperature coefficient, and the internal resistances r1, r2 and r3 between the two ends of the first, second and third cables are all equal.

8. A three-wire thermal resistance measurement system according to claim 7, characterized in that: The currents output by the first constant current source I1 and the second constant current source I2 are equal.

9. A three-wire thermal resistance measurement method using the system of claim 8, characterized in that: include: Control the first switch SSR1 and the second switch SSR2 to be turned off, and obtain the voltage difference U output by the output circuit at this time AB ; Control the first switch SSR1 and the second switch SSR2 to turn on, and obtain the voltage difference U' output by the output circuit at this time AB ; Calculate the difference between the two voltage differences and use the following formula to calculate the resistance R of the thermal resistor Rt based on the difference t , the formula is: Wherein, I is the output current value of the first and second constant current sources, G is the amplification factor of the output circuit; R3 is the resistance value of the bias resistor R3.

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