CN219798574U - Test circuit for thermocouple detection - Google Patents
Test circuit for thermocouple detection Download PDFInfo
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- CN219798574U CN219798574U CN202321218806.9U CN202321218806U CN219798574U CN 219798574 U CN219798574 U CN 219798574U CN 202321218806 U CN202321218806 U CN 202321218806U CN 219798574 U CN219798574 U CN 219798574U
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- detection
- test circuit
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- temperature
- resistor
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- 238000001514 detection method Methods 0.000 title claims abstract description 43
- 238000012360 testing method Methods 0.000 title claims abstract description 17
- 238000001816 cooling Methods 0.000 abstract description 2
- 238000010438 heat treatment Methods 0.000 abstract description 2
- 238000000034 method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000012795 verification Methods 0.000 description 1
Abstract
The test circuit for thermocouple detection comprises a multi-bit digital signal input end, a resistor string formed by connecting a plurality of resistors in series, wherein one end of the resistor string is grounded, each resistor is connected with a switching tube in parallel, each signal wire of the digital signal input end is respectively connected with the control end of the switching tube and is connected with a digital-to-analog converter, any point which is not grounded in the resistor string is used as a detection point, and the output end of the digital-to-analog converter is respectively connected with the first input end and the second input end of an operational amplifier. By adopting the test circuit for thermocouple detection, the detection circuit part of the temperature sensor can be rapidly detected without heating and cooling operation, and the detection efficiency of the temperature sensor is improved.
Description
Technical Field
The utility model belongs to the technical field of electronics, and particularly relates to a test circuit for thermocouple detection.
Background
The thermocouple, i.e. the temperature sensor, is a circuit module for detecting temperature, and is generally composed of a temperature sensitive resistor and a detection circuit connected with the temperature sensitive resistor, wherein the detection circuit outputs an analog voltage signal as a temperature detection signal by detecting voltage or current changes on the temperature sensitive resistor.
The temperature-sensitive resistor in the temperature sensor is an electronic element with the resistance value capable of changing along with the temperature, a temperature sensor manufacturer produces a detection circuit board matched with the temperature-sensitive resistor, and the temperature-sensitive resistor is welded on the circuit board to assemble the temperature sensor, wherein the detection circuit board also generally comprises a constant current source for outputting constant current for generating voltage drop on the temperature-sensitive resistor, and the voltage drop can be detected through a voltage amplifier such as an operational amplifier.
For the performance test of the finished product of the temperature sensor, the temperature sensor is usually required to be placed in a refrigerator and an oven at a low temperature and a high temperature respectively by changing the external temperature change performance, the temperature rising and reducing process is long, and the actual detection process finds that if the temperature sensor cannot work normally, the temperature sensor is problematic in a detection circuit in most cases, and the probability of occurrence of the problem is very small because the temperature-sensitive resistor is a single electronic element.
Disclosure of Invention
In order to improve the testing efficiency of a temperature sensor, the utility model discloses a testing circuit for thermocouple detection.
The utility model relates to a test circuit for thermocouple detection, which comprises a multi-bit digital signal input end, a resistor string formed by connecting a plurality of resistors in series, wherein one end of the resistor string is grounded, each resistor is connected with a switching tube in parallel, each signal wire of the digital signal input end is respectively connected with the control end of the switching tube and is connected with a digital-to-analog converter, any point which is not grounded in the resistor string is used as a detection point, and the output end of the digital-to-analog converter is connected with the first input end of an operational amplifier.
Preferably, the detection point is the other end of the resistor string, which is not grounded.
Preferably, the output end of the operational amplifier is also connected with an analog-to-digital converter.
Preferably, the resistances of the resistor strings are equal, or are arranged in an equal-ratio array according to the resistance value.
Preferably, the switch tube is a MOS tube.
By adopting the test circuit for thermocouple detection, the detection circuit part of the temperature sensor can be rapidly detected without heating and cooling operation, and the detection efficiency of the temperature sensor is improved.
Drawings
FIG. 1 is a schematic diagram of a test circuit for thermocouple detection according to one embodiment of the present utility model;
the reference sign name in the figure is M-switch tube; r-resistance; AMP-op AMP; an ADC-analog-to-digital converter, DAC-digital-to-analog converter; an OUT-output terminal; p1-a temperature-sensitive resistor access end; p2-the output of the detection circuit.
Description of the embodiments
The following describes the present utility model in further detail.
For the purpose of making the objects, technical solutions and advantages of the present utility model more apparent, the technical solutions of the present utility model will be clearly and completely explained below in connection with the detailed description of the present utility model and the corresponding drawings, and it is obvious that the described embodiments are only some, but not all, embodiments of the present utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
The utility model relates to a test circuit for thermocouple detection, which comprises a multi-bit digital signal input end, a resistor string formed by connecting a plurality of resistors R in series, wherein one end of the resistor string is grounded, each resistor is connected with a switching tube M in parallel, each signal wire of the digital signal input end is respectively connected with the control end of the switching tube and is connected with a digital-to-analog converter DAC, any point which is not grounded in the resistor string is used as a detection point, and the output end of the digital-to-analog converter is connected with the first input end of an operational amplifier.
The temperature-sensing resistor detection circuit is a complete circuit except that the temperature-sensing resistor is not welded, as shown in fig. 1, and generally comprises a constant current source and a voltage amplifier, wherein a temperature-sensing resistor access end P1 of the temperature-sensing resistor detection circuit is connected to the top of a resistor string to serve as a detection point, the temperature-sensing resistor detection circuit is connected with the ground wire of the resistor string, and an output end of the temperature-sensing resistor detection circuit is connected to a second input end of the operational amplifier.
For the convenience of explanation of the working principle of the utility model, it is assumed that the digital signal input end is a four-bit signal, all resistors of the resistor string are equal, and the switching tube inputs high level to be disconnected and low level to be connected. The switching tube can be an MOS tube with small on resistance.
When the digital signal input end is (1111), all the switching tubes are disconnected, all the resistors of the resistor string are not short-circuited, and all the resistors are connected into the circuit. The constant current source outputs a current to generate a maximum voltage drop V1 across all resistors, and a voltage signal is output to a voltage amplifier of the temperature sensor detection circuit through a detection circuit output terminal P2 of the temperature sensor detection circuit.
Meanwhile, the digital signal is input into the digital-to-analog converter, converted into an analog voltage signal V2 through the digital-to-analog converter, the V1 and the V2 are input into the operational amplifier AMP at the same time, the operational amplifier detects the difference value of the two signals, if the difference value is within a preset range, the tested circuit is indicated to work normally, and if the difference value exceeds the preset range, the tested circuit is indicated to work abnormally.
The external digital signal generator can continuously generate a series of digital signals through the preprogramming, and continuously changes from the digital signal input end according to the rules of 1111, 1110, 1100, 1000 and 0000, for example, the number of connected resistors is continuously reduced, and the continuous change of the temperature-sensitive resistor under the temperature change is simulated.
In a preferred embodiment, the resistances of the individual resistors are typically arranged in an equal ratio array, e.g., 1,2,4,8 ohms, where the digital signal changes according to 1111, 1110, 1101, 1100, law, as is well known to those skilled in the art, and a more precise change in resistance can be achieved with a minimum of 1 ohm for each adjustment of the series resistance. The digital signal can be input by simulating the temperature curve of the temperature-sensitive resistor and discontinuously changing.
In a preferred embodiment, the output end OUT of the operational amplifier is also connected with an analog-to-digital converter ADC, the output signal of the operational amplifier is converted into a digital signal, and the digital signal is directly displayed by connecting an external display tube, so that the observation result is more convenient. In one embodiment, the operational amplifier employs LM2904DT, and the analog to digital converter and digital to analog converter employ AD7680BRM and AD5504BRUZ, respectively.
By adopting the test circuit for thermocouple detection, provided by the utility model, the continuous change of the resistance value is controlled through the digital signal, the resistance value change of the temperature-sensitive resistor caused by the temperature is simulated, the detection circuit part of the temperature sensor can be rapidly detected, the temperature rise and reduction operation is not needed, and the detection efficiency of the temperature sensor is improved.
The foregoing description of the preferred embodiments of the present utility model is not obvious contradiction or on the premise of a certain preferred embodiment, but all the preferred embodiments can be used in any overlapped combination, and the embodiments and specific parameters in the embodiments are only for clearly describing the utility model verification process of the inventor and are not intended to limit the scope of the utility model, and the scope of the utility model is still subject to the claims, and all equivalent structural changes made by applying the specification and the content of the drawings of the present utility model are included in the scope of the utility model.
Claims (5)
1. The utility model provides a test circuit for thermocouple detection, its characterized in that includes the digital signal input of multiposition, the resistance cluster that comprises a plurality of resistance series connection, resistance cluster one end ground connection has a switch tube for every resistance parallelly connected, each signal line of digital signal input connects the control end of switch tube respectively to connect a digital analog converter, the arbitrary point of non-ground in the resistance cluster is as the check point, the output of digital analog converter connects operational amplifier's first input.
2. The test circuit for thermocouple detection as recited in claim 1, wherein said detection point is the other end of the resistor string which is not grounded.
3. The test circuit for thermocouple detection as recited in claim 1, wherein an analog-to-digital converter is further connected to the output of said operational amplifier.
4. The test circuit for thermocouple detection as recited in claim 1, wherein said resistor strings are arranged such that the respective resistances are equal or in equal-ratio series.
5. The test circuit for thermocouple detection according to claim 1, wherein said switching tube is a MOS tube.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321218806.9U CN219798574U (en) | 2023-05-19 | 2023-05-19 | Test circuit for thermocouple detection |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202321218806.9U CN219798574U (en) | 2023-05-19 | 2023-05-19 | Test circuit for thermocouple detection |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN219798574U true CN219798574U (en) | 2023-10-03 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202321218806.9U Active CN219798574U (en) | 2023-05-19 | 2023-05-19 | Test circuit for thermocouple detection |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN219798574U (en) |
-
2023
- 2023-05-19 CN CN202321218806.9U patent/CN219798574U/en active Active
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