Thermocouple demodulation temperature sensor

Abstract

The invention belongs to the field of temperature sensor design, and particularly relates to a thermocouple demodulation temperature sensor. A platinum resistor temperature measurement scheme is adopted by an existing temperature sensor capable of demodulating output at present, the use requirement of a wide temperature measurement interval cannot be met, and the actual use requirement of an airborne superior system cannot be met. The device comprises a shell, an armored thermocouple assembly, a signal conditioning circuit, a bracket and an electric connector, the armored thermocouple assembly comprises a K-type thermocouple alloy wire packaged by magnesium oxide powder in a shell, and a compensation lead is connected at the tail end of the K-type thermocouple alloy wire and then penetrates out of the cold end sleeve. The signal conditioning circuit adopts an external diode to measure and compensate the temperature of the cold end of the thermocouple, and a voltage signal of the thermocouple is converted into a 4-20mA current signal through sensor calibration of a built-in MCU of a signal conditioning chip and a peripheral V / I conversion circuit. The wide temperature range from-55 DEG C to 945 DEG C can be measured, cold end compensation and linear compensation functions are achieved, and temperature drift caused by thermocouple cold end environment changes can be eliminated.

Description

Technical Field

[0001] The invention belongs to the field of temperature sensor design, and in particular relates to a thermocouple demodulation temperature sensor. Background Art

[0002] In the application field of aircraft temperature sensors, the temperature of the wheel brake disc needs to be controlled in real time when the aircraft brakes during landing. At the same time, during the braking process, the ambient temperature around the wheel will change, and the thermocouple signal must be compensated and demodulated before it can be used.

[0003] Currently, the existing temperature sensors with demodulated output use platinum resistance temperature measurement solutions, and their temperature measurement range is -60 to 400°C, which does not meet the requirements of a wide temperature measurement range; or the existing thermocouple temperature sensors do not have the function of compensation and demodulation output of 4 to 20mA current, and cannot meet the actual use requirements of the airborne upper system. Summary of the invention

[0004] The purpose of the present invention is to provide a temperature sensor based on thermocouple demodulation to meet the needs of aircraft for real-time and accurate measurement of wheel brake disc temperature.

[0005] The invention discloses a thermocouple demodulation temperature sensor, comprising a shell, an armored thermocouple assembly installed at the front end of the shell, a signal conditioning circuit installed in the shell, and a bracket and an electrical connector installed at the rear end of the shell; wherein the armored thermocouple assembly comprises a K-type thermocouple alloy wire encapsulated by magnesium oxide powder in the shell, and a compensation wire is connected to the end of the K-type thermocouple alloy wire and passes through a cold end sleeve; the signal conditioning circuit adopts an external diode to measure the cold end temperature of the compensation thermocouple, and converts the voltage signal of the thermocouple into a current signal of 4-20 mA through the sensor calibration of the built-in MCU of the signal conditioning chip and the peripheral V / I conversion circuit.

[0006] Advantageously, the input zero position of the signal conditioning circuit corresponds to a 4mA current output, and the input full scale corresponds to a 20mA current output.

[0007] Advantageously, the external diode temperature sensor is placed close to the cold end of the thermocouple.

[0008] Advantageously, the front end of the power supply circuit uses a diode for reverse protection, a transient voltage suppression diode for surge protection, and a magnetic bead to suppress high-frequency signals coupled to the input and output lines.

[0009] Advantageously, the signal conditioning chip and an external field effect transistor form a voltage control circuit to convert a 28V power supply into a 5V power supply to drive a back-end circuit.

[0010] Advantageously, the front end of the K-type thermocouple alloy wire is located at the frontmost end of the armored thermocouple assembly.

[0011] Advantageously, the compensation wire is welded to a K-type thermocouple alloy wire.

[0012] Advantageously, the seal is secured with a high temperature epoxy resin after welding.

[0013] Beneficial effects: The temperature sensor based on thermocouple demodulation proposed in the present invention can measure a wide temperature range of -55 to 945°C, and has cold-end compensation and linear compensation functions. It can eliminate the temperature drift caused by changes in the cold-end environment of the thermocouple, accurately calculate and output 4 to 20mA current signals, has high temperature measurement accuracy, simple circuit design, and has high practical application value.

[0014] The features, functions, and advantages that have been discussed can be achieved independently in various examples or may be combined in yet other examples. Further details of the examples can be seen with reference to the following description and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Examples, as well as preferred modes of use, other objects and description thereof, will be best understood by reference to the following detailed description of examples of the invention when read in conjunction with the accompanying drawings, in which:

[0016] Figure 1 It is a schematic diagram of the composition of the temperature sensor;

[0017] Figure 2 This is the working principle diagram of the temperature sensor;

[0018] Figure 3 It is a schematic diagram of the armored thermocouple assembly;

[0019] Figure 4 is a schematic diagram of the power supply circuit;

[0020] Figure 5 This is the schematic diagram of the signal conditioning circuit.

[0021] 1. Armored thermocouple assembly, 2. Shell, 3. Signal conditioning circuit, 4. Bracket, 5. Electrical connector; 6. Shell, 7. K-type thermocouple alloy wire, 8. Magnesium oxide powder, 9. Cold end sleeve, 10. Compensation wire DETAILED DESCRIPTION

[0022] The disclosed examples will be more fully described with reference to the accompanying drawings, in which some (but not all) of the disclosed examples are shown. In fact, many different examples may be described and these examples should not be construed as limited to the examples set forth herein. Instead, these examples are described so that this disclosure will be thorough and complete and will fully convey the scope of the disclosure to those skilled in the art.

[0023] See also Figure 1The temperature sensor embodiment based on thermocouple demodulation shown includes an armored thermocouple assembly 1, a housing 2, a signal conditioning circuit 3, a bracket 4, an electrical connector 5, etc.

[0024] like Figure 2 As shown, the armored thermocouple assembly 1 adopts the thermocouple temperature measurement principle to convert the external temperature signal into a millivolt voltage signal, and the signal conditioning circuit 3 amplifies and compensates the millivolt voltage signal output by the armored thermocouple assembly 1 and outputs a current signal.

[0025] like Figure 3 As shown, the armored thermocouple assembly 1 is composed of a housing 6, a K-type thermocouple alloy wire 7, a cold end sleeve 9 and a compensation wire 10. The K-type thermocouple alloy wire 7 is used as a temperature sensing element for design, and a K-type thermocouple with a Class II accuracy is selected, and its temperature measurement range is -55 to 1200°C, and the accuracy is: ±2.5°C-55 to 333°C, ±0.0075|t|°C333 to 1200°C. The K-type thermocouple alloy wire 7 is filled and encapsulated in the housing 6 by magnesium oxide powder 8. The magnesium oxide powder 8 has good thermal conductivity and insulation performance, which can ensure the insulation strength between the K-type thermocouple alloy wire 7 and the temperature probe. The front end of the K-type thermocouple alloy wire 7 is at the front end of the armored thermocouple assembly 1, ensuring that the K-type thermocouple alloy wire 7 can quickly sense the temperature signal, thereby ensuring the thermal response time of the armored thermocouple assembly 1. After the compensation wire 10 is welded to the K-type thermocouple alloy wire 7, it is fixed and sealed with high-temperature epoxy resin.

[0026] like Figure 4 In the power supply circuit shown, a diode is used at the front end of the power supply for reverse protection, a transient voltage suppression diode is used for surge protection, and a magnetic bead is used to suppress high-frequency signals coupled to the input and output lines. A signal conditioning chip and an external field effect transistor form a voltage control circuit to convert the 28V power supply into a 5V power supply to drive the back-end circuit.

[0027] like Figure 5 The signal conditioning circuit shown uses an external diode to measure and compensate the cold end temperature of the thermocouple. The external diode temperature sensor is placed as close to the cold end of the thermocouple as possible. The use of an external diode for temperature measurement and compensation can effectively reduce the output error caused by inconsistent cold end temperature. The voltage signal of the thermocouple is converted into a 4-20mA current signal through the sensor calibration algorithm of the built-in MCU of the signal conditioning chip and the peripheral V / I conversion circuit, and the input zero position corresponds to a 4mA current output, and the input full scale corresponds to a 20mA current output.

[0028] Descriptions of different advantageous arrangements have been presented for purposes of illustration and description, but the description is not intended to be exclusive or limited to examples of the disclosed form. Many modifications and variations will be apparent to those of ordinary skill in the art. Additionally, different advantageous examples may be described as having different advantages over other advantageous examples. The selected example or examples are selected and described in order to best illustrate the principles of the examples, practical applications, and to enable those of ordinary skill in the art to understand the disclosure as having various examples with various modifications suitable for the particular use contemplated.

Claims

1. A thermocouple demodulation temperature sensor, characterized in that: The invention comprises a housing (2), an armored thermocouple assembly (1) installed at the front end of the housing (2), a signal conditioning circuit (3) installed in the housing (2), and a bracket (4) and an electrical connector (5) installed at the rear end of the housing (2); wherein the armored thermocouple assembly (1) comprises a K-type thermocouple alloy wire (7) encapsulated by magnesium oxide powder (8) in a housing (6), and a compensation wire (10) is connected to the end of the K-type thermocouple alloy wire (7) and then passes through a cold end sleeve (9); the signal conditioning circuit uses an external diode to measure the cold end temperature of the compensation thermocouple, and converts the voltage signal of the thermocouple into a current signal of 4 to 20 mA through sensor calibration of an MCU built into a signal conditioning chip and a peripheral V / I conversion circuit.

2. The thermocouple demodulation temperature sensor according to claim 1, characterized in that: The input zero position of the signal conditioning circuit corresponds to a 4mA current output, and the input full scale corresponds to a 20mA current output.

3. The thermocouple demodulation temperature sensor according to claim 1, characterized in that: The external diode temperature sensor is placed close to the cold end of the thermocouple.

4. The thermocouple demodulation temperature sensor according to claim 1, characterized in that: The front end of the power supply circuit adopts a diode for anti-reverse protection, adopts a transient voltage suppression diode for surge protection, and adopts a magnetic bead to suppress high-frequency signals coupled to the input and output lines.

5. The thermocouple demodulation temperature sensor according to claim 1, characterized in that: The signal conditioning chip and the external field effect transistor form a voltage control circuit to convert the 28V power supply into a 5V power supply to drive the back-end circuit.

6. The thermocouple demodulation temperature sensor according to claim 1, characterized in that: The front end of the K-type thermocouple alloy wire (7) is located at the front end of the armored thermocouple assembly (1).

7. The thermocouple demodulation temperature sensor according to claim 1, characterized in that: The compensation wire (10) is welded to the K-type thermocouple alloy wire (7).

8. The thermocouple demodulation temperature sensor according to claim 7, characterized in that: After welding, high temperature epoxy resin is used to fix and seal.

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