Digital output temperature transmitter

Abstract

This utility model relates to a digital output temperature transmitter, which includes an electrically connected signal acquisition and processing circuit and a platinum resistance thermometer; the signal acquisition and processing circuit includes an analog sensor signal processing circuit, a signal isolation circuit, a signal amplification circuit and an analog-to-digital conversion circuit connected in sequence; this utility model is reasonably designed, compact in structure and easy to use.

Description

Technical Field

[0001] This utility model relates to the field of electronic technology, specifically to a digital output temperature transmitter, particularly for applications where temperature measurement is converted into digital signals, and where easy system integration, strong anti-interference capability, and high reliability are required. Background Technology

[0002] Temperature is a crucial physical quantity affecting industrial and agricultural production, scientific research, environmental protection, meteorology, and even daily life. Achieving accurate measurement is of great significance. Temperature measuring instruments, in particular, require high accuracy, high reliability, and low cost.

[0003] The PT1000 platinum resistance thermometer is one of the most commonly used temperature sensors in industrial production processes. Platinum resistance thermometers are characterized by their wide measurement range, high accuracy, good stability, and oxidation resistance, making them widely used in the medium and low temperature range.

[0004] The formula governing the change of platinum resistance thermometers with temperature is as follows: R t =R0[1+A t +Bt 2 +Ct 3 (t-100℃)]-200℃~0℃ R t =R0(1+At+Bt 2 0℃~600℃ In the formula, R t This represents the resistance value of the platinum resistance element at temperature t. R0 is the resistance value of the platinum resistance element at 0℃; A, B, and C are scale division constants; t represents the temperature of the medium being measured.

[0005] This demonstrates a non-linear relationship between the resistance of the PT1000 platinum resistance thermometer and temperature. In applications, an unbalanced bridge circuit is typically used to convert the resistance change of the PT1000 sensor into a voltage. However, when the PT1000 is connected to a temperature-measuring bridge circuit, the non-linearity between the bridge arm resistance and the bridge output voltage increases further due to the non-linear relationship between the bridge output voltage and temperature. The non-linearity of the PT1000 and the inherent non-linearity of the unbalanced temperature-measuring bridge introduce significant non-linear errors in temperature measurement, and the analog output signal is easily affected by external interference. Therefore, it is necessary to perform non-linearity correction and digital conversion of the analog output signal.

[0006] Traditional temperature transmitters are implemented using analog and microcontroller technologies. While analog temperature transmitters are inexpensive, they rely on potentiometers (or resistors) to adjust the zero and full-scale readings, making it difficult to achieve high calibration accuracy. Furthermore, potentiometers drift over time, resulting in poor reliability and stability, which directly leads to limited measurement accuracy. Microcontroller-based temperature transmitters use software for nonlinear correction and software adjustment of the zero and full-scale readings, offering high measurement accuracy and reliability. However, microcontrollers are more expensive, hindering mass production, and their application in high and low temperature environments is limited.

[0007] Existing temperature transmitters are implemented using analog and microcontroller technologies. While analog temperature transmitters are inexpensive, they rely on potentiometers (or resistors) to adjust the zero and full-scale readings, making it difficult to achieve high calibration accuracy. Furthermore, potentiometers drift over time, resulting in poor reliability and interference resistance, which directly leads to limited measurement accuracy. Microcontroller-based temperature transmitters use software for nonlinear correction and software adjustment of the zero and full-scale readings, offering high measurement accuracy and reliability. However, they are more expensive, hindering mass production and limiting their applications. Utility Model Content

[0008] The technical problem this invention aims to solve is that existing temperature transmitters using analog technology suffer from poor reliability and anti-interference capabilities, making it difficult to improve measurement accuracy; while temperature transmitters using microcontroller technology are expensive and have limited applications. This invention provides a digital output temperature transmitter that achieves high temperature measurement accuracy, digital output function, temperature compensation function, strong anti-interference capability, good stability, low cost, and wide application range.

[0009] The technical problem to be solved by this utility model is to provide a digital output temperature transmitter. To solve the above problems, the technical solution adopted by this utility model is as follows: A digital output temperature transmitter includes an electrically connected signal acquisition and processing circuit and a platinum resistance thermometer; the signal acquisition and processing circuit includes an analog sensor signal processing circuit, a signal isolation circuit, a signal amplification circuit, and an analog-to-digital conversion circuit connected in sequence. The analog sensor signal processing circuit includes an analog sensor signal processor U4 and resistors RB1-3, R1, R2, and capacitors C1 and C2. In the analog sensor signal processor U4, there are resistors RB1-3, R1, R2, and capacitors C1 and C2. Resistors RB1-3 form an unbalanced bridge; the platinum resistance thermometer serves as one arm resistor of the unbalanced bridge. The platinum resistance thermometer is connected to three circuits: one circuit is connected to resistor RB3, the second circuit is connected to pin 4, and the third circuit is grounded through resistor R1. Connect resistor RB3 to pin 6 on one side and resistor RB2 on the other side. One path of resistor RB2 is connected to pin 5, and the other path is connected to pin 4 through resistor RB1. Pin 7 is connected to +5V, and +5V is grounded through parallel capacitors C1 and C2. +5V is connected to pin 9. Pins 15 and 3 are grounded respectively, and pin 14 is connected to pin 13; The output signals from pins 2 and 11 are connected to the signal isolation circuit.

[0010] As a further improvement to the above technical solution: The platinum resistance thermometer is either PT1000 or PT100, and it uses a three-wire system.

[0011] The signal isolation circuit includes chip U3 and chips C3 and C4; In chip U3, pin 1 is connected to +5V and grounded through capacitor C3; Pin 8 is connected to +5V and grounded through capacitor C4; Pins 3, 4, and 5 are grounded respectively; Pins 6 and 7 output signals are respectively connected to the isolation circuit; Pin 2 is connected to the output terminal of analog sensor signal processor U4.

[0012] The signal amplification circuit includes amplifier U2; In amplifier U2, pin 7 is connected to +5V, and pin 4 is grounded; Connect resistor R6 between pin 2 and pin 6; Pin 6 of chip U3 is connected to pin 2 of amplifier U2 via resistor R4; Pin 7 of chip U3 is connected to pin 3 of amplifier U2 and resistor R5 through resistor R3; resistor R5 is grounded.

[0013] The analog-to-digital conversion circuit includes chip U1. In chip U1, pin 7 is connected to pin 6 of the output terminal of amplifier U2 in the signal amplification circuit through resistor R7; Pin 7 is grounded through capacitor C5; Pin 2 is grounded through resistor R10; Pin 6 is split into three circuits, connected to resistor R11, capacitor C6, and pin 1 respectively; Resistor R11 and capacitor C6 are grounded together through resistor R8; Pin 3 output is connected to the FPGA; Pin 4 is grounded; Pin 8 is connected to +5V and connected to pin 5 through resistor R9; Pin 5 is grounded through capacitor C7. Digital output temperature transmitters convert temperature signals into corresponding digital signals, which can be compensated by first-order linear correction or by matching a specific temperature curve.

[0014] The digital output temperature transmitter provided by this utility model has high temperature measurement accuracy, temperature compensation function, strong anti-interference ability and good stability, is easy and flexible to use, low cost and wide range of applications.

[0015] This utility model is reasonably designed, low in cost, sturdy and durable, safe and reliable, simple to operate, time-saving and labor-saving, cost-saving, compact in structure and easy to use. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall circuit of this utility model.

[0017] Figure 2 This is the utility model Figure 1 A partial circuit diagram on the left.

[0018] Figure 3 This is the utility model Figure 2 A partial circuit diagram on the left. Detailed Implementation like Figure 1-3 As shown, the digital output temperature transmitter of this embodiment includes a signal acquisition and processing circuit 1 and a platinum resistance thermometer 2 that are electrically connected; the signal acquisition and processing circuit 1 includes an analog sensor signal processing circuit 11, a signal isolation circuit 12, a signal amplification circuit 13 and an analog-to-digital conversion circuit 14 that are electrically connected in sequence. The analog sensor signal processing circuit 11 includes an analog sensor signal processor U4 and resistors RB1-3, R1, R2, and capacitors C1 and C2. In the analog sensor signal processor U4, there are resistors RB1-3, R1, R2, and capacitors C1 and C2. Resistors RB1-3 form an unbalanced bridge; platinum resistance 2 serves as one arm resistor of the unbalanced bridge. The platinum resistance thermometer is connected to three circuits: one circuit is connected to resistor RB3, the second circuit is connected to pin 4, and the third circuit is grounded through resistor R1. Connect resistor RB3 to pin 6 on one side and resistor RB2 on the other side. One path of resistor RB2 is connected to pin 5, and the other path is connected to pin 4 through resistor RB1. Pin 7 is connected to +5V, and +5V is grounded through parallel capacitors C1 and C2. +5V is connected to pin 9. Pins 15 and 3 are grounded respectively, and pin 14 is connected to pin 13; The output signals from pins 2 and 11 are connected to signal isolation circuit 12.

[0019] Platinum resistance 2 is a platinum resistance PT1000 or PT100, using a three-wire system.

[0020] The signal isolation circuit 12 includes chip U3 and chips C3 and C4; In chip U3, pin 1 is connected to +5V and grounded through capacitor C3; Pin 8 is connected to +5V and grounded through capacitor C4; Pins 3, 4, and 5 are grounded respectively; Pins 6 and 7 output signals are respectively connected to isolation circuit 12; Pin 2 is connected to the output terminal of analog sensor signal processor U4.

[0021] Signal amplification circuit 13 includes amplifier U2; In amplifier U2, pin 7 is connected to +5V, and pin 4 is grounded; Connect resistor R6 between pin 2 and pin 6; Pin 6 of chip U3 is connected to pin 2 of amplifier U2 via resistor R4; Pin 7 of chip U3 is connected to pin 3 of amplifier U2 and resistor R5 through resistor R3; resistor R5 is grounded.

[0022] The analog-to-digital conversion circuit 14 includes chip U1. In chip U1, pin 7 is connected to pin 6 of amplifier U2 output terminal of signal amplifier circuit 13 through resistor R7; Pin 7 is grounded through capacitor C5; Pin 2 is grounded through resistor R10; Pin 6 is split into three circuits, connected to resistor R11, capacitor C6, and pin 1 respectively; Resistor R11 and capacitor C6 are grounded together through resistor R8; Pin 3 output is connected to the FPGA; Pin 4 is grounded; Pin 8 is connected to +5V and connected to pin 5 through resistor R9; Pin 5 is grounded through capacitor C7.

[0023] like Figure 1-3This is a digital output temperature transmitter, mainly divided into two parts: a signal acquisition and processing circuit 1 and a platinum resistance thermometer 2. The signal acquisition and processing circuit 1 includes an analog sensor signal processing circuit 11, a signal isolation circuit 12, a signal amplification circuit 13, and an analog-to-digital conversion circuit 14. The platinum resistance thermometer 2 can be a PT1000 or PT100, three-wire type. The functions of the signal acquisition and processing circuit are performed by an analog sensor signal processor, which uses the HKA2910 from Xi'an Xiangteng Company. This processor includes a programmable sensor excitation, a 16-stage programmable gain amplifier, a 768-byte internal FLASH, four 16-bit DACs, a general-purpose operational amplifier, and an embedded temperature sensor.

[0024] The basic principle of the digital output temperature transmitter is as follows: the analog sensor signal processing circuit 11 uses a three-wire platinum resistance thermometer in an unbalanced bridge configuration. The platinum resistance acts as one arm of the bridge, greatly reducing the additional error caused by the wire resistance. Based on the characteristic that the resistance of the platinum resistance changes with temperature, the acquired resistance value changes, and the corresponding voltage value is output to the signal isolation circuit 12 for isolation between the preceding and following stages, reducing interference and further improving accuracy. The voltage signal is then amplified by the signal amplification circuit 13, and finally converted from analog to digital signal by the analog-to-digital conversion circuit 14, improving the anti-interference capability of the output signal and completing the transmission of the temperature signal to a digital signal. Finally, the FPGA reads the signal and converts it into temperature.

[0025] This digital output temperature transmitter features temperature compensation, allowing users to select 1 to 114 temperature points for simple first-order linear correction or to match a specific temperature curve to compensate for the sensor's temperature response. It can program up to 114 independent 16-bit FLASH units and perform corrections at 1.5°C intervals within the range of -55°C to 125°C. After calibration, the error can be reduced to near the inherent characteristics of a bridge sensor.

[0026] This utility model is described in detail for the purpose of making the disclosure clearer, and the prior art will not be listed one by one.

[0027] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. It is obvious to those skilled in the art that multiple technical solutions of this utility model can be combined. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model. All technical contents not described in detail in this utility model are publicly known technologies.

Claims

1. A digital output temperature transmitter, characterized in that: The signal acquisition and processing circuit (1) and platinum resistance thermometer (2) are electrically connected; the signal acquisition and processing circuit (1) includes an analog sensor signal processing circuit (11), a signal isolation circuit (12), a signal amplification circuit (13), and an analog-to-digital conversion circuit (14) that are electrically connected in sequence. The analog sensor signal processing circuit (11) includes an analog sensor signal processor U4 and resistors RB1-3, R1, R2, and capacitors C1 and C2. In the analog sensor signal processor U4, there are resistors RB1-3, R1, R2, and capacitors C1 and C2. Resistors RB1-3 form an unbalanced bridge; platinum resistance (2) serves as one arm resistor of the unbalanced bridge; The platinum resistance (2) is connected to three circuits: one circuit is connected to resistor RB3, the second circuit is connected to pin 4, and the third circuit is grounded through resistor R1. Connect resistor RB3 to pin 6 on one side and resistor RB2 on the other side. One path of resistor RB2 is connected to pin 5, and the other path is connected to pin 4 through resistor RB1. Pin 7 is connected to +5V, and +5V is grounded through parallel capacitors C1 and C2. +5V is connected to pin 9. Pins 15 and 3 are grounded respectively, and pin 14 is connected to pin 13; The output signals of pins 2 and 11 are connected to the signal isolation circuit (12).

2. The digital output temperature transmitter according to claim 1, characterized in that: The platinum resistance (2) is a platinum resistance PT1000 or PT100, using a three-wire system.

3. The digital output temperature transmitter according to claim 1, characterized in that: The signal isolation circuit (12) includes chip U3 and chips C3 and C4; In chip U3, pin 1 is connected to +5V and grounded through capacitor C3; Pin 8 is connected to +5V and grounded through capacitor C4; Pins 3, 4, and 5 are grounded respectively; The output signals of pins 6 and 7 are respectively connected to the isolation circuit (12); Pin 2 is connected to the output terminal of analog sensor signal processor U4.

4. The digital output temperature transmitter according to claim 1, characterized in that: The signal amplification circuit (13) includes amplifier U2; In amplifier U2, pin 7 is connected to +5V, and pin 4 is grounded; Connect resistor R6 between pin 2 and pin 6; Pin 6 of chip U3 is connected to pin 2 of amplifier U2 via resistor R4; Pin 7 of chip U3 is connected to pin 3 of amplifier U2 and resistor R5 through resistor R3; resistor R5 is grounded.

5. The digital output temperature transmitter according to claim 1, characterized in that: The analog-to-digital conversion circuit (14) includes chip U1, In chip U1, pin 7 is connected to pin 6 of the output terminal of amplifier U2 in signal amplification circuit (13) through resistor R7; Pin 7 is grounded through capacitor C5; Pin 2 is grounded through resistor R10; Pin 6 is split into three circuits, connected to resistor R11, capacitor C6, and pin 1 respectively; Resistor R11 and capacitor C6 are grounded together through resistor R8; Pin 3 output is connected to the FPGA; Pin 4 is grounded; Pin 8 is connected to +5V and connected to pin 5 through resistor R9; Pin 5 is grounded through capacitor C7.

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