Testing device based on arm model heat flow

Abstract

The utility model aims to provide the testing device based on the arm model heat flow, which is low in cost, can meet uv-level voltage testing requirements, can realize voltage testing of a plurality of channels, and can improve the testing efficiency. The device comprises an arm model, a heat flux sensor, a temperature sensor, an operational amplifier, an instrumentation amplifier, an analog-to-digital converter and a main control board, the heat flux sensor and the temperature sensor are both mounted on the surface of the arm model, the temperature sensor is mounted on the surface of a product, the temperature sensor is connected with the main control board, and the operational amplifier is connected with the main control board. The heat flux sensor is connected with the input end of the operational amplifier, the operational amplifier increases input impedance, the output end of the operational amplifier is connected with the input end of the instrument amplifier and amplifies and converts signals into differential analog signals, the output end of the instrument amplifier is connected with the 24-bit analog-to-digital converter, and the analog-to-digital converter is connected into an external upper computer through the main control board. The device is applied to the technical field of heat flux testing.

Description

Technical Field

[0001] The utility model is applied to the technical field of heat flux testing, and particularly relates to a testing device based on arm model heat flow. Background Art

[0002] Heat flux refers to the amount of heat energy passing through a unit area per unit time. It is a directional vector and its unit in the International System of Units is W / ㎡, that is, watts per square meter. There are currently two main methods for heat flux testing. The commonly known but usually impractical method is to measure the temperature difference across a piece of material with a known thermal conductivity. This method is similar to the standard method of measuring electric current, in which the voltage drop across a known resistor is measured. This method is usually difficult to perform because the thermal resistance of the material being tested is usually unknown. In order to determine the thermal resistance, accurate material thickness and thermal conductivity values ​​are required. Heat flux can be indirectly calculated using thermal resistance and temperature measurements on both sides of the material. Another method is to directly measure the amount of heat transferred to the surface on which the heat flux sensor is installed by using a heat flux sensor (heat flux sensor) or a heat flux sensor. Since the heat flux sensor can realize on-site measurement of the existing heat flux by using the Seebeck effect, there is no need to confirm the thermal resistance and conductivity of the material. In the second method, the heat flux sensor can be mounted on the surface of the object, and the heat flux can be calculated by measuring the output voltage of the sensor. The heat flux of the arm model can be detected by the second method mentioned above. A heat flux sensor can be used to detect the heat flux transmitted upward from the inside of the arm model. Because the temperature inside the arm model is relatively low, the voltage output of the heat flux sensor is low, only UV or even NV level, but ordinary instruments cannot meet the test requirements, so a high-precision digital multimeter is required, and the sensitivity of the heat flux sensor must be high enough. However, the cost of a high-precision digital multimeter is high, so it is necessary to provide a low-cost test device based on the heat flow of the arm model that can solve the UV level voltage test requirements, realize multiple channel voltage testing, and improve test efficiency. Utility Model Content

[0003] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide a testing device based on arm model heat flow which is low-cost, can meet the requirements of UV-level voltage testing, can realize voltage testing of multiple channels, and improves testing efficiency.

[0004] The technical solution adopted by the utility model is: the utility model includes an arm model, a heat flux sensor, a temperature sensor, an operational amplifier, an instrument amplifier, an analog-to-digital converter and a main control board, the heat flux sensor and the temperature sensor are both mounted on the surface of the arm model, the temperature sensor is mounted on the surface of the product, the temperature sensor is connected to the main control board, the heat flux sensor is connected to the input end of the operational amplifier, the operational amplifier increases the input impedance, the output end of the operational amplifier is connected to the input end of the instrument amplifier, the signal is amplified and converted into a differential analog signal, the output end of the instrument amplifier is connected to the 24-bit analog-to-digital converter, and the analog-to-digital converter is connected to an external host computer via the main control board.

[0005] It can be seen from the above scheme that the present application can replace the expensive general multimeter, has low cost and high measurement accuracy, can be used in a variety of scenarios, is compatible with 4-channel heat flux measurement, can solve UV-level voltage testing requirements, and greatly improve test efficiency.

[0006] A preferred solution is that the arm model heat flow-based testing device also includes a multiplexer, and the heat flux sensor is connected to the input end of the operational amplifier via the multiplexer.

[0007] A preferred solution is that the VIN_P pin of the operational amplifier is connected to the DA pin of the multiplexer, the VIN_N pin of the operational amplifier is connected to the DB pin of the multiplexer, the VOUT_P pin of the operational amplifier is connected to the VIN_P pin of the instrumentation amplifier, and the VOUT_N pin of the operational amplifier is connected to the VIN_N pin of the instrumentation amplifier.

[0008] A preferred solution is that the arm model heat flow-based testing device also includes a first resistor and a second resistor, the same-direction input terminal of the instrument amplifier is connected to the reverse input terminal of the instrument amplifier via the first resistor, the reverse input terminal of the instrument amplifier is connected to the VOUT_N pin of the operational amplifier, and the same-direction input terminal of the instrument amplifier is connected to the VOUT_P pin of the operational amplifier via the second resistor.

[0009] A preferred solution is that the Analog_out_N pin and the Analog_out_P pin of the analog-to-digital converter are connected to the corresponding pins of the instrument amplifier, and the ADC_DOUT pin, ADC_SCLK pin, ADC_nCS pin, and ADC_DIN pin of the analog-to-digital converter are all connected to the corresponding pins of the main control board. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1It is a structural block diagram of the utility model;

[0011] Figure 2 It is the principle diagram of the utility model;

[0012] Figure 3 is a circuit schematic diagram of the operational amplifier;

[0013] Figure 4 is a circuit schematic diagram of the instrument amplifier;

[0014] Figure 5 is a circuit schematic diagram of the analog-to-digital converter;

[0015] Figure 6 is a schematic diagram of the multiplexer;

[0016] Figure 7 It is a comparison diagram of the voltage value detected by the utility model and the multimeter;

[0017] Figure 8 is a diagram illustrating the wires of the heat flux sensor;

[0018] Fig. 9 It is a test temperature diagram of the temperature sensor. DETAILED DESCRIPTION

[0019] like Figures 1 to 3 As shown, in this embodiment, the utility model includes an arm model 1, a heat flux sensor 2, a temperature sensor 3, an operational amplifier U1, an instrument amplifier U2, an analog-to-digital converter U3 and a main control board 4, the heat flux sensor 2 and the temperature sensor 3 are both mounted on the surface of the arm model 1, the temperature sensor 3 is mounted on the surface of the product, the temperature sensor 3 is connected to the main control board 4, the heat flux sensor 2 is connected to the input end of the operational amplifier U1, the operational amplifier U1 increases the input impedance, the output end of the operational amplifier U1 is connected to the input end of the instrument amplifier U2, the signal is amplified and converted into a differential analog signal, the output end of the instrument amplifier U2 is connected to the 24-bit analog-to-digital converter U3, and the analog-to-digital converter U3 is connected to the external host computer 5 via the main control board 4.

[0020] If a relatively expensive high-precision digital multimeter is used as a testing tool, the arm model 1 is heated by its own heating rod, and the heat source is transmitted to the surface of the product, the heat flux sensor 2 and the temperature sensor 3. The heat flux sensor 2 converts the heat flux signal into a voltage signal, and the voltage is measured by a digital multimeter model DMM-ELM3704. The surface temperature of the product is detected by the temperature sensor 3, and the heat flux on the surface of the product is calculated by the measured temperature and voltage signals through the heat flux calculation formula.

[0021] This application reduces the testing cost by replacing the digital multimeter with the operational amplifier U1, the instrumentation amplifier U2, and the analog-to-digital converter U3. The heat flux sensor 2 is the first low-cost heat flux density sensor on the market. It has the smallest thickness while still maintaining good sensitivity. The heat flux sensor 2 is flexible enough to be easily attached to a circular surface, and its high sensitivity design makes it an ideal choice for accurately measuring relatively low heat fluxes. The model of the heat flux sensor 2 is HFS-5. Compared with other sensors, the HFS-5 thin film contact heat flux sensor is more suitable for measuring the heat flux of the arm in this application. It is easier to contact the surface of the circular arm, increasing the accuracy of the detection.

[0022] The heat flux sensor 2 is mounted on the surface of the arm model 1 to measure the heat flux. The voltage wire and the thermocouple integrated wire of the heat flux sensor 2 are connected to a precision voltmeter or a precision data acquisition device for measurement. The voltage wire of the heat flux sensor 2 reads the analog DC voltage signal from the wire to collect the measurement value. The positive (+) terminal of the voltage measuring device is connected to the left first wire, and the negative (-) terminal is connected to the left second wire. The sensitivity of the heat flux sensor can be adjusted according to the temperature of the sensor and the function based on the temperature, and the heat flux is calculated using the adjusted sensitivity. The wire description of the heat flux sensor 2 is as follows: Figure 8 shown.

[0023] The heat flux formula is as follows:

[0024] The output signal of the heat flux sensor 2 has a certain relationship with the temperature of the sensor itself. This correlation means that the sensitivity of the sensor will change slightly at different temperatures, and the temperature measurement value of the sensor is obtained in time at each measurement. Combined with calibrated sensitivity The heat flux sensitivity at that specific temperature is then determined The heat flux sensitivity formula is as follows:

[0025] like Fig. 9As shown, in this embodiment, in a precise temperature control place, it is first necessary to ensure the test accuracy of the temperature sensor 3. The model of the temperature sensor 3 is TMP117. The thermocouple calibration process of the heat flux sensor 2 itself is complicated, and the measured temperature has a large error. Compared with the temperature detection of the thermocouple itself, the temperature detection of TMP117 will be simpler. TMP117 only needs 1 group of I2C, and the thermocouple needs a complete temperature measurement circuit. The circuit design will be more concise. At the same time, TMP1117 is more convenient than the thermocouple self-calibration during calibration, and the measurement accuracy is more accurate than the thermocouple. This application uses the TMP117 temperature measurement module to read the temperature, so as to calculate the heat flux sensitivity at that temperature.

[0026] In addition, TMP117 is a high-precision digital temperature sensor. It is designed to meet the ASTM E1112 and ISO 80601 requirements for medical electronic thermometers. TMP117 can provide 16-bit temperature results with a resolution of 0.0078°C and can achieve up to ±0.1°C accuracy in the temperature range of -20°C to 50°C without calibration. TMP117 has an interface compatible with I2C and SMBus™, has a programmable alarm function, supports up to four devices on a single bus, and includes an integrated EEPROM for device programming and an additional 48-bit memory for general applications. The temperature sensor 3 is a high-precision, low-power digital temperature sensor. The temperature sensor 3 is placed close to the surface of the arm model 1, and the voltage signal generated by the sensor is converted into a temperature value through its own ADC module. The read temperature is applied to the sensitivity calculation of the heat flux sensor. The 48-bit general-purpose EEPROM of TMP117 can be used to store calibration parameters. The TMP117 module is a PCB soft board, which can better contact the surface of the arm model 1, and the sensed temperature is more accurate. The soft board uses 4 TMP117, and I2C uses an external MCU to connect to the soft board. The MCU reads the temperature of the 4 TMP117 and takes the average value to calculate the surface temperature of the arm model. TMP117 is compatible with I2C communication. Using 4 TMP117 sensors in a TMP117 board can further improve the accuracy and reliability of temperature testing.

[0027] like Figure 6As shown, in this embodiment, the arm model heat flow test device further includes a multiplexer 6, and the heat flux sensor 2 is connected to the input end of the operational amplifier U1 via the multiplexer 6. The model of the multiplexer 6 is ADG1408, which is a single-chip multiplexer with 8 single channels and 4 differential channels built in. ADG1408 switches one of the 8 inputs to a common output according to the address determined by the 3-bit binary address lines A0, A1 and A2. ADG1408 provides an EN input to enable or disable the device; when disabled, all channels are turned off.

[0028] like Figure 3 As shown, in this embodiment, the VIN_P pin of the operational amplifier U1 is connected to the DA pin of the multiplexer 6, the VIN_N pin of the operational amplifier U1 is connected to the DB pin of the multiplexer 6, the VOUT_P pin of the operational amplifier U1 is connected to the VIN_P pin of the instrumentation amplifier U2, and the VOUT_N pin of the operational amplifier U1 is connected to the VIN_N pin of the instrumentation amplifier U2. The operational amplifier U1 uses the ADA4522-2 chip, which is a dual-channel, zero-drift, low-noise, low-power amplifier with an input of 0 V and rail-to-rail output when powered by a single power supply, and is optimized for total accuracy that varies with time, temperature, and voltage conditions. The device has a wide operating voltage and temperature range, high open-loop gain, and extremely low DC and AC errors, making it very suitable for amplifying small input signals and accurately amplifying signals in various applications.

[0029] like Figure 4 As shown, in this embodiment, the arm model heat flow test device further includes a first resistor R2 and a second resistor R1, the same-direction input terminal of the instrument amplifier U2 is connected to the reverse input terminal of the instrument amplifier U2 via the first resistor R2, the reverse input terminal of the instrument amplifier U2 is connected to the VOUT_N pin of the operational amplifier U1, and the same-direction input terminal of the instrument amplifier U2 is connected to the VOUT_P pin of the operational amplifier U1 via the second resistor R1. The resistance values ​​of the first resistor R2 and the second resistor R1 are both 10K, and the signal to be collected is amplified by the instrument amplifier U2 to amplify the small voltage. The model of the instrument amplifier U2 is AD8221, and its gain is set by an external resistor. This application uses a 200-fold gain to amplify the small voltage input by the heat flux sensor, and the external resistor is calculated by the formula:

[0030] like Figure 5As shown, in this embodiment, the Analog_out_N pin and the Analog_out_P pin of the analog-to-digital converter U3 are connected to the corresponding pins of the instrument amplifier U2, and the ADC_DOUT pin, ADC_SCLK pin, ADC_nCS pin, and ADC_DIN pin of the analog-to-digital converter U3 are all connected to the corresponding pins of the main control board 4. The model of the analog-to-digital converter U3 is AD7175-2, which is an integrated low-noise, fast-settling, multiplexed analog-to-digital converter that can meet the high-precision amplification gain ADC required by this design. The device is powered by 5 V AVDD1 or ±2.5 V AVDD1 / AVSS, 2 V to 5 V AVDD2, and IOVDD power supplies.

[0031] like Figures 1 to 8 As shown, in this embodiment, there are four voltage signal channels for measuring the heat flux sensor 2, the multiplexer 6 selects one measurement channel, the voltage signal is amplified by the operational amplifier U1, the instrument amplifier U2 converts the single-ended signal into a differential signal, and the analog-to-digital converter U3 reads the processed voltage. When the analog-to-digital converter U3 detects the voltage signal of the heat flux sensor 2 after amplification, the required voltage value can be obtained through calculation, and the average temperature obtained by the temperature sensor 3 of the four channels is obtained and brought into the heat flux sensor calculation formula mentioned above, and the heat flux on the surface of the arm model 1 is obtained by measuring the voltage and temperature. This application can replace the multimeter to detect the small voltage of the sensor on the surface of the arm model 1, such as Figures 7 and 8 As shown, 200 sets of small voltage data were measured by DMM / 34461A in the form of resistor voltage division, and 0.1mV and 0.2mV voltages were measured respectively. The voltage values ​​measured by this application are similar to the voltage values ​​detected by the multimeter, with a small error.

[0032] In this embodiment, the following table is a heat flux measurement data table of the utility model:

Claims

1. A test device based on arm model heat flow, characterized in that: It comprises an arm model (1), a heat flux sensor (2), a temperature sensor (3), an operational amplifier (U1), an instrument amplifier (U2), an analog-to-digital converter (U3) and a main control board (4). The heat flux sensor (2) and the temperature sensor (3) are both mounted on the surface of the arm model (1), the temperature sensor (3) is mounted on the surface of the product, the temperature sensor (3) is connected to the main control board (4), the heat flux sensor (2) is connected to the input end of the operational amplifier (U1), the operational amplifier (U1) increases the input impedance, the output end of the operational amplifier (U1) is connected to the input end of the instrument amplifier (U2), the signal is amplified and converted into a differential analog signal, the output end of the instrument amplifier (U2) is connected to the 24-bit analog-to-digital converter (U3), and the analog-to-digital converter (U3) is connected to an external host computer (5) via the main control board (4).

2. The arm model heat flow testing device according to claim 1, characterized in that: The arm model heat flow testing device further comprises a multiplexer (6), and the heat flux sensor (2) is connected to the input end of the operational amplifier (U1) via the multiplexer (6).

3. The arm model heat flow testing device according to claim 2, characterized in that: The VIN_P pin of the operational amplifier (U1) is connected to the DA pin of the multiplexer (6), the VIN_N pin of the operational amplifier (U1) is connected to the DB pin of the multiplexer (6), the VOUT_P pin of the operational amplifier (U1) is connected to the VIN_P pin of the instrumentation amplifier (U2), and the VOUT_N pin of the operational amplifier (U1) is connected to the VIN_N pin of the instrumentation amplifier (U2).

4. The arm model heat flow testing device according to claim 3, characterized in that: The arm model heat flow testing device further comprises a first resistor (R2) and a second resistor (R1); the same-direction input end of the instrument amplifier (U2) is connected to the reverse input end of the instrument amplifier (U2) via the first resistor (R2); the reverse input end of the instrument amplifier (U2) is connected to the VOUT_N pin of the operational amplifier (U1); and the same-direction input end of the instrument amplifier (U2) is connected to the VOUT_P pin of the operational amplifier (U1) via the second resistor (R1).

5. The arm model heat flow testing device according to claim 1, characterized in that: The Analog_out_N pin and the Analog_out_P pin of the analog-to-digital converter (U3) are connected to the corresponding pins of the instrument amplifier (U2), and the ADC_DOUT pin, the ADC_SCLK pin, the ADC_nCS pin, and the ADC_DIN pin of the analog-to-digital converter (U3) are all connected to the corresponding pins of the main control board (4).

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