Ultralow-temperature calibration-free temperature measuring device and method

Abstract

The invention discloses an ultralow-temperature calibration-free temperature measuring device and method. The ultralow-temperature calibration-free temperature measuring device comprises a temperature sensor, a shielding cable, an electric connector, a signal conditioning circuit, an instrument amplifier, a filter circuit and a microcontroller, wherein the temperature sensor is used for generating a voltage drop signal after sensing the external temperature and outputting the voltage drop signal to the signal conditioning circuit; the signal conditioning circuit carries out filtering and electromagnetic compatibility processing on the voltage drop signal to generate a differential voltage signal and outputs the differential voltage signal to the instrument amplifier; the instrument amplifier is used for amplifying the differential voltage signal and outputting a single-end voltage signal to the filter circuit; the filter circuit filters the single-end voltage signal and then sends the signal to the microcontroller; and the microcontroller is used for analyzing and compensating the filtered single-end voltage signal to obtain a temperature value.

Description

Technical Field

[0001] The invention relates to an ultra-low temperature calibration-free temperature measurement device and method, belonging to the technical field of measurement devices. Background Art

[0002] When a liquid rocket engine is working, the internal temperature of the engine needs to be monitored in real time. Since the propellants of the cryogenic liquid engine are liquid hydrogen and liquid oxygen, the temperature measurement range of the hydrogen turbine pump wall temperature is 25~323K. Therefore, the temperature sensor is required to have a wide temperature measurement range and be able to accurately measure the actual temperature of the measured point in an ultra-low temperature environment.

[0003] At present, the temperature measurement of liquid rocket engines generally adopts thermocouples, thermal resistors, semiconductor thermistors, etc., which have good measurement accuracy in the medium and high temperature range, but their sensitivity will be seriously reduced in ultra-low temperature environment, and their accuracy and versatility will also be reduced accordingly, and their use is relatively limited. For example, when the platinum resistor is above 70K, its measurement accuracy is 1.3K. When it is below 70K, each platinum resistor needs to be calibrated separately, and the standard temperature-resistance scale cannot be used. It is not universal, and its ultra-low temperature calibration cost is dozens of times the cost of the sensor. It is not suitable for mass delivery and use, and the product engineering application capability is low. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art and to provide an ultra-low temperature calibration-free temperature measurement device and method, the measurement device has a simple and reliable structure, a small size, a low cost and a wide temperature measurement range.

[0005] The technical solution of the present invention is:

[0006] The present invention discloses an ultra-low temperature calibration-free temperature measurement device, comprising: a temperature sensor, a shielded cable, an electrical connector, a signal conditioning circuit, an instrument amplifier, a filter circuit and a microcontroller; wherein:

[0007] The temperature sensor senses the external temperature, generates a voltage drop signal, and outputs it to the signal conditioning circuit;

[0008] The signal conditioning circuit generates a differential voltage signal after filtering and performing electromagnetic compatibility processing on the voltage drop signal and outputs the signal to the instrumentation amplifier;

[0009] The instrumentation amplifier amplifies the differential voltage signal and outputs a single-ended voltage signal to the filter circuit;

[0010] A filter circuit filters the single-ended voltage signal and sends it to the microcontroller;

[0011] The microcontroller analyzes and compensates the filtered single-ended voltage signal to obtain a temperature value.

[0012] Furthermore, in the above device, the temperature sensor includes a temperature sensing element, a sensitive element silicon diode, a shielded cable and an electrical connector; wherein,

[0013] After the temperature sensing element senses the external temperature, it transmits the measured temperature to the sensitive element silicon diode through heat conduction;

[0014] The voltage drop across the pins of the silicon diode changes, generating a voltage drop signal;

[0015] The voltage drop signal is transmitted through the shielded cable to the electrical connector and output to the signal conditioning circuit.

[0016] Furthermore, in the above device, the electromagnetic compatibility circuit includes: common mode inductors and capacitors, which form an LC filter to filter the input signal and output a differential voltage signal to a back-end acquisition channel.

[0017] Furthermore, in the above device, the signal conditioning circuit includes: a three-op-amp amplifier and a second-order low-pass filter circuit; wherein,

[0018] The three-op-amp amplifier amplifies the input differential voltage signal and outputs the voltage Vout to the second-order low-pass filter circuit;

[0019] The second-order low-pass filter circuit performs low-pass filtering on the amplified voltage Vout and sends it to the microcontroller.

[0020] Furthermore, in the above device, the three operational amplifiers include operational amplifiers A1, A2 and A3, resistors R135, R136, R137, R138, R139, R140, and R143; wherein,

[0021] The positive input terminal of the operational amplifier A1 is connected to the positive voltage of the differential voltage; the negative input terminal of the operational amplifier A1 is connected to the input terminals of R137 and R138; the output terminal is connected to the input terminal of the resistor R135 and the output terminal of R137;

[0022] The output end of R135 is connected to the input end of R136, and the output end of R136 is grounded;

[0023] The positive input terminal of the operational amplifier A2 is connected to the negative voltage of the differential voltage; the negative input terminal of the operational amplifier A2 is connected to the output terminal of R138 and the input terminal of R139;

[0024] The output terminal of the operational amplifier A2 is connected to the output terminal of R139 and the input terminal of R140;

[0025] The output terminal of R140 is connected to the negative input terminal of operational amplifier A3 and the input terminal of R143;

[0026] The output terminal of R135 is connected to the positive input terminal of operational amplifier A3;

[0027] The output terminal of R143 is connected to the output terminal of operational amplifier A3;

[0028] The operational amplifier A3 outputs a voltage Vout to the second-order low-pass filter circuit.

[0029] Furthermore, in the above device,

[0030] Vout=(1+2R / R G )(V2-V1)

[0031] V2-V1=(Temp-IN+)-(Temp-IN-)

[0032] Where, R is the resistance value of R135, R136, R137, R139, R140, and R143; R G is the resistance value of R138; Temp-IN+ is the positive voltage value of the differential voltage, and Temp-IN- is the negative voltage value of the differential voltage.

[0033] Furthermore, in the above device, the secondary low-pass filter includes an operational amplifier A4, resistors R141, R142, and capacitors C148, C150; wherein,

[0034] The input end of the resistor R141 is connected to the output voltage Vout; the output end of the resistor R141 is connected to the input end of the resistor R142 and the input end of the capacitor C148;

[0035] The output end of the resistor R142 is connected to the input end of the capacitor C150, and the output end of the capacitor C150 is connected to the ground and the positive input end of the operational amplifier A4;

[0036] A negative input terminal of the operational amplifier A4 is connected to an output terminal of the capacitor C148 and an output terminal of the operational amplifier A4.

[0037] Furthermore, in the above device, the operational amplifier is a zero-drift, rail-to-rail operational amplifier, providing an offset voltage of less than or equal to 5uV.

[0038] The present invention discloses an ultra-low temperature calibration-free temperature measurement method, comprising:

[0039] After sensing the external temperature through the temperature sensor, a voltage drop signal is generated;

[0040] After filtering and electromagnetic compatibility processing the voltage drop signal, a differential voltage signal is generated;

[0041] Amplify and filter the differential voltage signal, and output a filtered single-ended voltage signal;

[0042] According to the filtered single-ended voltage signal, the temperature value is obtained by looking up the silicon diode characteristic graduation table.

[0043] The beneficial effects of the present invention and the prior art are:

[0044] (1) The measuring device of the present invention has a simple and reliable structure, a small size, a low cost, a wide temperature measurement range, and no need to calibrate each sensor individually in an ultra-low temperature measurement environment. The parameters can be directly interpreted through the voltage drop and temperature standard curve of the silicon diode, and the versatility is strong.

[0045] (2) When a sensor of the present invention fails, it can be directly replaced without changing the subsequent data acquisition and processing algorithms, thereby meeting the measurement requirements of temperature parameters on the arrow.

[0046] (3) The present invention is calibration-free. The voltage change of the silicon diode pin and the temperature change felt by its sensitive end have a relatively stable corresponding relationship, and the corresponding relationship will not change with the change of the temperature zone. Therefore, it has strong versatility and does not need to calibrate each sensor separately.

[0047] (4) The present invention has high precision. The measurement accuracy can reach ±0.25K. The measurement accuracy of common platinum resistance temperature sensors is 1.3K at 70K. When the temperature is lower than 70K, the accuracy decreases and needs to be calibrated separately.

[0048] (5) The temperature measurement range of the present invention is wide. The temperature measurement range of the temperature sensor is 1.4K to 500K, which can well cover the temperature range of each temperature measurement point on the engine.

[0049] (6) The present invention is small in size and simple in structure. The sensitive element of the temperature sensor is a silicon diode, which has a simple structure and no complicated devices and circuits.

[0050] (7) The present invention is used to measure the wall temperature of a liquid hydrogen and liquid oxygen cryogenic rocket engine turbine pump. Compared with temperature sensors such as platinum resistance currently used in China, the temperature sensor can accurately measure temperature in an ultra-low temperature environment with a small deviation error and does not require separate calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the structure of the temperature sensor of the present invention;

[0052] Figure 2 It is a block diagram of the working principle of the temperature sensor of the present invention;

[0053] Figure 3 The electromagnetic compatibility circuit for outputting the signal of the temperature sensor of the present invention;

[0054] Figure 4 The output signal amplification and conditioning circuit of the temperature sensor of the present invention;

[0055] Figure 5 This is a standard curve diagram of voltage drop-temperature of the silicon diode of the present invention. DETAILED DESCRIPTION

[0056] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0057] The present invention discloses an ultra-low temperature calibration-free temperature measurement device, comprising: a temperature sensor, a shielded cable, an electrical connector, a signal conditioning circuit, an instrument amplifier, a filter circuit and a microcontroller; wherein:

[0058] The temperature sensor senses the external temperature, generates a voltage drop signal, and outputs it to the signal conditioning circuit;

[0059] The signal conditioning circuit generates a differential voltage signal after filtering and performing electromagnetic compatibility processing on the voltage drop signal and outputs the signal to the instrumentation amplifier;

[0060] The instrumentation amplifier amplifies the differential voltage signal and outputs a single-ended voltage signal to the filter circuit;

[0061] A filter circuit filters the single-ended voltage signal and sends it to the microcontroller;

[0062] The microcontroller analyzes and compensates the filtered single-ended voltage signal to obtain a temperature value.

[0063] Preferably, the temperature sensor comprises a temperature sensing element, a sensitive element silicon diode, a shielded cable and an electrical connector; wherein,

[0064] After the temperature sensing element senses the external temperature, it transmits the measured temperature to the sensitive element silicon diode through heat conduction;

[0065] The voltage drop across the pins of the silicon diode changes, generating a voltage drop signal;

[0066] The voltage drop signal is transmitted through the shielded cable to the electrical connector and output to the signal conditioning circuit.

[0067] Preferably, the electromagnetic compatibility circuit includes: common mode inductors and capacitors, which form an LC filter to filter the input signal and output a differential voltage signal to a back-end acquisition channel.

[0068] Preferably, the signal conditioning circuit comprises: a three-op-amp amplifier and a second-order low-pass filter circuit; wherein,

[0069] The three-op-amp amplifier amplifies the input differential voltage signal and outputs the voltage Vout to the second-order low-pass filter circuit;

[0070] The second-order low-pass filter circuit performs low-pass filtering on the amplified voltage Vout and sends it to the microcontroller.

[0071] Preferably, the three-op-amp amplifier comprises operational amplifiers A1, A2 and A3, and resistors R135, R136, R137, R138, R139, R140 and R143; wherein,

[0072] The positive input terminal of the operational amplifier A1 is connected to the positive voltage of the differential voltage; the negative input terminal of the operational amplifier A1 is connected to the input terminals of R137 and R138; the output terminal is connected to the input terminal of the resistor R135 and the output terminal of R137;

[0073] The output end of R135 is connected to the input end of R136, and the output end of R136 is grounded;

[0074] The positive input terminal of the operational amplifier A2 is connected to the negative voltage of the differential voltage; the negative input terminal of the operational amplifier A2 is connected to the output terminal of R138 and the input terminal of R139;

[0075] The output terminal of the operational amplifier A2 is connected to the output terminal of R139 and the input terminal of R140;

[0076] The output terminal of R140 is connected to the negative input terminal of operational amplifier A3 and the input terminal of R143;

[0077] The output terminal of R135 is connected to the positive input terminal of operational amplifier A3;

[0078] The output terminal of R143 is connected to the output terminal of operational amplifier A3;

[0079] The operational amplifier A3 outputs a voltage Vout to the second-order low-pass filter circuit.

[0080] Preferably,

[0081] Vout=(1+2R / R G )(V2-V1)

[0082] V2-V1=(Temp-IN+)-(Temp-IN-)

[0083] Where, R is the resistance value of R135, R136, R137, R139, R140, and R143; R G is the resistance value of R138; Temp-IN+ is the positive voltage value of the differential voltage, and Temp-IN- is the negative voltage value of the differential voltage.

[0084] Preferably, the secondary low-pass filter includes an operational amplifier A4, resistors R141, R142, and capacitors C148, C150; wherein,

[0085] The input end of the resistor R141 is connected to the output voltage Vout; the output end of the resistor R141 is connected to the input end of the resistor R142 and the input end of the capacitor C148;

[0086] The output end of the resistor R142 is connected to the input end of the capacitor C150, and the output end of the capacitor C150 is connected to the ground and the positive input end of the operational amplifier A4;

[0087] A negative input terminal of the operational amplifier A4 is connected to an output terminal of the capacitor C148 and an output terminal of the operational amplifier A4.

[0088] Preferably, the operational amplifier is a zero-drift, rail-to-rail operational amplifier, providing an offset voltage of 5uV or less, and having the characteristics of low noise, low offset and low power.

[0089] The present invention discloses an ultra-low temperature calibration-free temperature measurement method, comprising:

[0090] After sensing the external temperature through the temperature sensor, a voltage drop signal is generated;

[0091] After filtering and electromagnetic compatibility processing the voltage drop signal, a differential voltage signal is generated;

[0092] Amplify and filter the differential voltage signal, and output a filtered single-ended voltage signal;

[0093] According to the filtered single-ended voltage signal, the temperature value is obtained by looking up the silicon diode characteristic graduation table.

[0094] Example

[0095] The temperature measuring device in the present invention is composed of a temperature sensor and a collection device. The temperature sensor is used to measure the temperature signal and transmit it to the back-end collection channel. The collection device is used to integrate and collect the measurement signals from various types of sensors, and process the sensor signals through the signal conditioning circuit inside the collection device, and transmit them to the host computer through the communication module.

[0096] a. As attached Figure 1 The figure shows the schematic diagram of the structure of the temperature sensor. The temperature sensor consists of a sensitive element silicon diode, a housing, a cable, and a connector.

[0097] b. As attached Figure 2 As shown, the measurement method of the temperature sensor is to attach the sensitive end of the silicon diode temperature sensor to the surface of the measured point. After the silicon diode is sensitive to the temperature, the voltage drop across its pins changes.

[0098] c. The sensor outputs the voltage drop change between the two pins of the silicon diode to the back-end signal conditioning circuit through a low-temperature resistant shielded cable and an electrical connector.

[0099] d. As attached Figure 3 As shown, the output voltage of the temperature sensor is filtered through common mode inductors, filter capacitors and other devices. The electromagnetic compatibility circuit converts the signal into a differential voltage signal for output. The electromagnetic compatibility circuit mainly uses common mode inductors, capacitors and other common filter components. The output voltage of the temperature sensor passes through common mode inductors (L210, L211), filter capacitors (C241~C252) and other devices to form an LC filter to filter the input signal. The electromagnetic compatibility circuit converts the signal into a differential voltage signal and outputs it to the back-end acquisition channel.

[0100] e. As attached Figure 4 As shown in FIG. 1 , the voltage signal after being filtered by the electromagnetic compatibility circuit enters the instrument amplifier (three op amps) built by the operational amplifier F8552Z to form an amplification and conditioning circuit, as shown in FIG. Figure 4 As shown, the above-mentioned filtered differential voltage signals Temp-IN+ and Temp-IN- enter the amplification and conditioning circuit from the positive input terminals of the two 8552 operational amplifiers A1 and A2 respectively. A1 and A2 form a common-mode amplifier, and A3 is a differential amplifier. The output terminal Vout of the three operational amplifiers formed by A1, A2, and A3 is (1+2R / R G )(V2-V1). The resistance values ​​of R135, R136, R137, R139, R140, and R143 are all R, and the resistance value of R138 is R G , V2-V1=(Temp-IN+)-(Temp-IN-).

[0101] The amplified voltage signal Vout is sent to the microcontroller through the second-order low-pass filter circuit formed by the back-end A4, and the final temperature value is obtained according to the silicon diode voltage-temperature scale. The operational amplifier F8552SZ is a zero-drift, rail-to-rail operational amplifier, and provides very low offset voltage (maximum 5uV), with low noise, low offset and low power characteristics.

[0102] f. As attached Figure 5 As shown, the back-end microcontroller pre-sets an algorithm based on the voltage drop-temperature standard curve of the silicon diode to convert the processed signal into the corresponding temperature.

[0103] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

[0104] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. An ultra-low temperature calibration-free temperature measurement device, characterized in that: include: A temperature sensor, a shielded cable, an electrical connector, a signal conditioning circuit, an instrumentation amplifier, a filtering circuit, and a microcontroller; wherein, The temperature sensor senses the external temperature, generates a voltage drop signal, and outputs it to the signal conditioning circuit; The signal conditioning circuit generates a differential voltage signal after filtering and performing electromagnetic compatibility processing on the voltage drop signal and outputs the signal to the instrumentation amplifier; The instrumentation amplifier amplifies the differential voltage signal and outputs a single-ended voltage signal to the filter circuit; A filter circuit filters the single-ended voltage signal and sends it to the microcontroller; The microcontroller analyzes and compensates the filtered single-ended voltage signal to obtain a temperature value.

2. The ultra-low temperature calibration-free temperature measurement device according to claim 1, characterized in that: The temperature sensor comprises a temperature sensing element, a sensitive element silicon diode, a shielded cable and an electrical connector; wherein, After the temperature sensing element senses the external temperature, it transmits the measured temperature to the sensitive element silicon diode through heat conduction; The voltage drop across the pins of the silicon diode changes, generating a voltage drop signal; The voltage drop signal is transmitted through the shielded cable to the electrical connector and output to the signal conditioning circuit.

3. The ultra-low temperature calibration-free temperature measurement device according to claim 1, characterized in that: The electromagnetic compatibility circuit includes: common mode inductors and capacitors, which form an LC filter to filter the input signal and output a differential voltage signal to a back-end acquisition channel.

4. The ultra-low temperature calibration-free temperature measurement device according to claim 1, characterized in that: The signal conditioning circuit comprises: a three-op-amp amplifier and a second-order low-pass filter circuit; wherein, The three-op-amp amplifier amplifies the input differential voltage signal and outputs the voltage Vout to the second-order low-pass filter circuit; The second-order low-pass filter circuit performs low-pass filtering on the amplified voltage Vout and sends it to the microcontroller.

5. The ultra-low temperature calibration-free temperature measurement device according to claim 4, characterized in that: The three-op-amp amplifier includes operational amplifiers A1, A2 and A3, resistors R135, R136, R137, R138, R139, R140 and R143; wherein, The positive input terminal of the operational amplifier A1 is connected to the positive voltage of the differential voltage; the negative input terminal of the operational amplifier A1 is connected to the input terminals of R137 and R138; the output terminal is connected to the input terminal of the resistor R135 and the output terminal of R137; The output end of R135 is connected to the input end of R136, and the output end of R136 is grounded; The positive input terminal of the operational amplifier A2 is connected to the negative voltage of the differential voltage; the negative input terminal of the operational amplifier A2 is connected to the output terminal of R138 and the input terminal of R139; The output terminal of the operational amplifier A2 is connected to the output terminal of R139 and the input terminal of R140; The output terminal of R140 is connected to the negative input terminal of operational amplifier A3 and the input terminal of R143; The output terminal of R135 is connected to the positive input terminal of operational amplifier A3; The output terminal of R143 is connected to the output terminal of operational amplifier A3; The operational amplifier A3 outputs a voltage Vout to the second-order low-pass filter circuit.

6. The ultra-low temperature calibration-free temperature measurement device according to claim 5, characterized in that: Vout=(1+2R / R G )(V2-V1) V2-V1=(Temp-IN+)-(Temp-IN-) Where, R is the resistance value of R135, R136, R137, R139, R140, and R143; R G is the resistance value of R138; Temp-IN+ is the positive voltage value of the differential voltage, and Temp-IN- is the negative voltage value of the differential voltage.

7. The ultra-low temperature calibration-free temperature measurement device according to claim 4, characterized in that: The secondary low-pass filter includes an operational amplifier A4, resistors R141, R142, and capacitors C148, C150; wherein, The input end of the resistor R141 is connected to the output voltage Vout; the output end of the resistor R141 is connected to the input end of the resistor R142 and the input end of the capacitor C148; The output end of the resistor R142 is connected to the input end of the capacitor C150, and the output end of the capacitor C150 is connected to the ground and the positive input end of the operational amplifier A4; A negative input terminal of the operational amplifier A4 is connected to an output terminal of the capacitor C148 and an output terminal of the operational amplifier A4.

8. The ultra-low temperature calibration-free temperature measurement device according to claim 7, characterized in that: The operational amplifier is a zero-drift, rail-to-rail operational amplifier that provides an offset voltage of less than or equal to 5uV.

9. A method for measuring ultra-low temperature without calibration, characterized in that: include: After sensing the external temperature through the temperature sensor, a voltage drop signal is generated; After filtering and electromagnetic compatibility processing the voltage drop signal, a differential voltage signal is generated; Amplify and filter the differential voltage signal, and output a filtered single-ended voltage signal; According to the filtered single-ended voltage signal, the temperature value is obtained by looking up the silicon diode characteristic graduation table.

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