A temperature sensing circuit based on platinum thermal resistor

Abstract

The utility model discloses a temperature sensing circuit based on platinum resistance, including operational amplifier U1, platinum resistance R1, resistance R3, resistance R4, resistance R5, diode D2, diode D3, electric capacity C4 and difference amplifier U2, the power supply of operational amplifier U1 VCC is connected with the power supply, and the output pin of operational amplifier U1 connects the first node, and the inverting input pin of operational amplifier U1 connects the second node, and the other end of resistance R5 is grounded, and the other end of resistance R3 is connected with the pin 2 of difference amplifier U2, and the other end of resistance R4 is connected with the anode of diode D3 and then is connected with the pin 3 of difference amplifier U2, and the pin 4 of difference amplifier U2 is connected with pin 5 and is grounded, and the pin 6 of difference amplifier U2 is connected with one end of resistance R5, and the other end of resistance R5 is connected with one end of electric capacity C4, and the other end of electric capacity C4 is grounded. The utility model discloses a platinum resistance R1 very good realization temperature measurement, and the temperature measurement precision is high.

Description

Technical Field

[0001] This utility model relates to the field of circuit technology, specifically a temperature sensing circuit based on platinum resistance thermometers. Background Technology

[0002] Temperature measurement is required in many products and applications, such as lighting fixtures, and is often achieved through temperature sensing circuits. Many existing temperature sensing circuits use passive components such as thermocouples and NTC thermistors. Thermocouples are dependent on external components for accuracy and suffer from poor performance and weak interference resistance in low-temperature environments. NTC thermistors have limitations such as narrow temperature range, poor linearity, low stability, and poor consistency, resulting in a need to improve temperature sensing accuracy. Therefore, a temperature sensing circuit with high accuracy is needed. Utility Model Content

[0003] To address the shortcomings of existing technologies, the purpose of this invention is to provide a temperature sensing circuit based on platinum resistance thermometers, which can solve the problems described in the background section.

[0004] The technical solution to achieve the purpose of this utility model is as follows: a temperature sensing circuit based on a platinum resistance thermometer, including an operational amplifier U1, a platinum resistance thermometer R1, a resistor R3, a resistor R4, a resistor R5, a diode D2, a diode D3, a capacitor C4, and a differential amplifier U2. The power supply terminal VCC of the operational amplifier U1 is connected to an external power supply. One output pin of the operational amplifier U1 is connected to a first node, which is the node formed by connecting one end of the platinum resistance thermometer R1 and one end of the resistor R4. The first node is also grounded. One inverting input pin of operational amplifier U1 is connected to the second node, which is formed by connecting the other end of platinum resistance thermometer R1, one end of resistor R3, and one end of resistor R5. The other end of resistor R5 is grounded. The other end of resistor R3 is connected to pin 2 of differential amplifier U2. The other end of resistor R4 is connected to the positive terminal of diode D3 and then connected to pin 3 of differential amplifier U2. The negative terminal of diode D3 is grounded. Pins 4 and 5 of differential amplifier U2 are connected and grounded together. Pin 6 of differential amplifier U2 is connected to one end of resistor R5. The other end of resistor R5 is connected to one end of capacitor C4 to form node NTC. The other end of capacitor C4 is grounded.

[0005] Furthermore, the platinum resistance thermometer R1 is a PT100 platinum resistance thermometer.

[0006] Furthermore, it also includes resistor R2 and capacitor C3. Pin 8 of differential amplifier U2 is connected to one end of resistor R2, the other end of resistor R2 is connected to pin 1 of differential amplifier U2, pin 7 of differential amplifier U2 is connected to one end of capacitor C3 and they are both connected to an external power supply, and the other end of capacitor C3 is grounded.

[0007] Furthermore, it also includes capacitor C2 and diode D1. One non-inverting input pin of the operational amplifier is connected to the positive terminal of diode D1 and one end of capacitor C2, respectively, and connected to an external power supply. The negative terminal of diode D1 is connected to one end of capacitor C2 and then grounded together.

[0008] Furthermore, the power supply terminal VCC of operational amplifier U1 is connected in series with capacitor C1 and then grounded.

[0009] Furthermore, the operational amplifier U1 is model LM324.

[0010] Furthermore, the differential amplifier U2 is an instrumentation amplifier, model AD623.

[0011] The beneficial effects of this utility model are: This utility model achieves temperature measurement well through platinum resistance thermometer R1, and has high temperature measurement accuracy, excellent linearity, strong long-term stability, wide temperature range, and strong environmental adaptability. Attached Figure Description

[0012] Figure 1 This is a circuit diagram of the present invention. Detailed Implementation

[0013] The present invention will be further described below with reference to the accompanying drawings and specific embodiments: like Figure 1 As shown, a temperature sensing circuit based on a platinum resistance thermometer includes an operational amplifier U1, a platinum resistance thermometer R1, resistors R3, R4, and R5, diodes D2 and D3, a capacitor C4, and a differential amplifier U2. The power supply terminal VCC of operational amplifier U1 is connected to an external power supply. One output pin of operational amplifier U1 (pin 3OUT in the figure) is connected to a first node, which is formed by connecting one end of the platinum resistance thermometer R1 and one end of resistor R4. This first node is also grounded. One inverting input pin of operational amplifier U1 (pin 3IN in the figure) is connected to a second node, which is formed by connecting the other end of the platinum resistance thermometer R1, one end of resistor R3, and one end of resistor R5. The other end of resistor R5 is grounded. The other end of resistor R3 is connected to pin 2 of differential amplifier U2. The other end of resistor R4 is connected to the anode of diode D3, and both are connected to pin 3 of differential amplifier U2. The cathode of diode D3 is grounded. Pins 4 and 5 of differential amplifier U2 are connected and grounded together. Pin 6 of differential amplifier U2 is connected to one end of resistor R5. The other end of resistor R5 is connected to one end of capacitor C4 to form node NTC. The other end of capacitor C4 is grounded.

[0014] Among them, the platinum resistance thermometer R1 is a PT100 platinum resistance thermometer.

[0015] It also includes resistor R2 and capacitor C3. Pin 8 of differential amplifier U2 is connected to one end of resistor R2, and the other end of resistor R2 is connected to pin 1 of differential amplifier U2. Pin 7 of differential amplifier U2 is connected to one end of capacitor C3 and they are both connected to an external power supply. The other end of capacitor C3 is grounded.

[0016] For example, it also includes capacitor C2 and diode D1. One non-inverting input pin of the operational amplifier is connected to the positive terminal of diode D1 and one end of capacitor C2, respectively, and is connected to an external power supply. The negative terminal of diode D1 is connected to one end of capacitor C2 and then grounded together.

[0017] For example, the power supply terminal VCC of operational amplifier U1 is connected in series with capacitor C1 and then grounded.

[0018] The operational amplifier U1 is model LM324.

[0019] For example, the differential amplifier U2 is an instrumentation amplifier, model AD623. The gain of the differential amplifier U2 is adjustable; in this embodiment, the gain of the differential amplifier U2 is set to 20 times.

[0020] A constant current source is constructed using operational amplifier U1. Operational amplifier U1 has internal negative feedback, allowing it to function as either a virtual short or virtual open circuit. When operational amplifier U1 is in a virtual short state, the voltage at its inverting input equals the voltage at its non-inverting input, which is 2.5V, serving as the reference voltage. Due to the virtual open circuit, no current flows through the input terminals of operational amplifier U1; that is, no current flows through either the inverting or non-inverting input. At this time, current flows from the output pin of operational amplifier U1 (3OUT in the diagram) and sequentially through resistors R1 and R5. With a reference voltage of 2.5V and a resistance of 24.9KΩ, the current flowing through the platinum resistance thermometer R1 is approximately 0.1mA. Therefore, operational amplifier U1 effectively provides a 0.1mA current excitation to the platinum resistance thermometer R1, thus functioning as a constant current source.

[0021] The current flowing through the platinum resistance thermometer R1 is converted into a voltage and input to the differential amplifier U2 in the subsequent stage. The differential amplifier amplifies the voltage, which is then filtered by a low-pass filter composed of resistor R5 and capacitor C4 before being output from node NTC. External devices (such as microcontrollers) can acquire the voltage through node NTC. The acquired voltage is then used to deduce the resistance value of the platinum resistance thermometer, and the ambient temperature can be calculated based on this resistance value, thus achieving temperature measurement.

[0022] Among them, diodes D1, D2 and D3 provide overvoltage protection and clamping, capacitor C2 is a filter capacitor and plays a filtering role, and resistors R3 and R4 limit the current to prevent excessive current from damaging the next stage.

[0023] This invention achieves excellent temperature measurement using a platinum resistance thermometer R1, exhibiting high accuracy, superior linearity, strong long-term stability, a wide temperature range, and strong environmental adaptability.

[0024] The embodiments disclosed in this specification are merely illustrative of one aspect of the present invention, and the scope of protection of the present invention is not limited to this embodiment. Any other functionally equivalent embodiments fall within the scope of protection of the present invention. Those skilled in the art can make various other corresponding changes and modifications based on the technical solutions and concepts described above, and all such changes and modifications should fall within the scope of protection of the claims of the present invention.

Claims

1. A temperature sensing circuit based on platinum resistance thermometers, characterized in that, The system includes operational amplifier U1, platinum resistance thermometer R1, resistors R3, R4, and R5, diode D2, diode D3, capacitor C4, and differential amplifier U2. Operational amplifier U1's power supply terminal VCC is connected to an external power supply. One output pin of operational amplifier U1 is connected to a first node, which is formed by connecting one end of platinum resistance thermometer R1 and one end of resistor R4. This first node is also grounded. One inverting input pin of operational amplifier U1 is connected to the second node, which is formed by connecting the other end of platinum resistance thermometer R1, one end of resistor R3, and one end of resistor R5. The other end of resistor R5 is grounded. The other end of resistor R3 is connected to pin 2 of differential amplifier U2. The other end of resistor R4 is connected to the positive terminal of diode D3 and then connected to pin 3 of differential amplifier U2. The negative terminal of diode D3 is grounded. Pins 4 and 5 of differential amplifier U2 are connected and grounded together. Pin 6 of differential amplifier U2 is connected to one end of resistor R5. The other end of resistor R5 is connected to one end of capacitor C4 to form node NTC. The other end of capacitor C4 is grounded.

2. The temperature sensing circuit based on platinum resistance thermometer according to claim 1, characterized in that, The platinum resistance thermometer R1 is a PT100 platinum resistance thermometer.

3. The temperature sensing circuit based on platinum resistance thermometer according to claim 1, characterized in that, It also includes resistor R2 and capacitor C3. Pin 8 of differential amplifier U2 is connected to one end of resistor R2, the other end of resistor R2 is connected to pin 1 of differential amplifier U2, pin 7 of differential amplifier U2 is connected to one end of capacitor C3 and they are both connected to an external power supply. The other end of capacitor C3 is grounded.

4. The temperature sensing circuit based on platinum resistance thermometer according to claim 3, characterized in that, It also includes capacitor C2 and diode D1. One non-inverting input pin of the operational amplifier is connected to the positive terminal of diode D1 and one end of capacitor C2, and an external power supply is connected. The negative terminal of diode D1 is connected to one end of capacitor C2 and then grounded together.

5. The temperature sensing circuit based on platinum resistance thermometer according to claim 4, characterized in that, The power supply terminal VCC of operational amplifier U1 is connected in series with capacitor C1 and then grounded.

6. The temperature sensing circuit based on platinum resistance thermometer according to any one of claims 1-5, characterized in that, The operational amplifier U1 is model LM324.

7. The temperature sensing circuit based on platinum resistance thermometer according to any one of claims 1-5, characterized in that, Differential amplifier U2 is an instrumentation amplifier, model number AD623.

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