[New patent introduction] How to improve the accuracy of thermal resistance temperature transmitter

Today, I will introduce a national invention authorized patent-a method to improve the accuracy of thermal resistance temperature transmitter. The patent was applied for by Chongqing Chuanyi Automation Co., Ltd., and the authorization was announced on June 29, 2018.

The invention relates to a control method of a thermal resistance temperature transmitter, in particular to a method for improving the accuracy of a thermal resistance temperature transmitter.

In the thermal resistance temperature transmitter product, because the AD collector collects the voltage signal, and the thermal resistance sensor outputs the resistance signal, there must be a constant current source flowing through the thermal resistance in the circuit to convert the resistance value into a voltage value; and The constant current source has a large temperature drift and is easily affected by the environment. When the constant current source is not accurate, it will affect the voltage value, and then affect the accuracy of the temperature transmitter. In order to eliminate the influence of the constant current source on the accuracy of the instrument, the traditional approach It is to choose a constant current source with low stability drift. This only reduces the impact of the temperature drift of the constant current source on the accuracy, but does not completely eliminate it; at the same time, due to the non-linear characteristics of the AD itself, it will also have a certain impact on the sampling accuracy.

Therefore, it is necessary to propose a method to improve the accuracy of the thermal resistance temperature transmitter, which can effectively eliminate the temperature drift of the constant current source and the influence of the nonlinear characteristics of the AD collector, and greatly improve the detection accuracy.

In view of this, the present invention provides a method for improving the accuracy of a thermal resistance temperature transmitter, which can effectively eliminate the influence of the temperature drift of the constant current source and the nonlinear characteristics of the AD collector, and greatly improve the detection accuracy.

The figure is a schematic diagram of the present invention.

The method for improving the accuracy of a thermal resistance temperature transmitter provided by the present invention at least includes an AD collector, a thermal resistance, and a precision resistance. The thermal resistance and the precision resistance form a series structure. Both ends of the thermal resistance and the precision resistance Both ends of the AD collector are connected to different acquisition channels of the AD collector; the linear calibration of the acquisition channel of the AD collector eliminates the accuracy impact, including the influence of the nonlinear characteristic of the AD collector and the influence of the nonlinear characteristic of the AD collector and the temperature drift of the constant current source. ; Among them, the calibration of the influence on the non-linear characteristics of the AD collector includes: before the AD collector is not connected with the thermal resistance, connect the standard resistance box with the thermal resistance acquisition channel of the AD collector, and the standard resistance box on the AD collector The acquisition channel is calibrated, and the resistance value of the thermal resistance channel of the AD collector is calculated by the formula Rz=k1*Mz+b1, where k1 and b1 are the calculation coefficients, and Mz is the code value of the thermal resistance connection channel collected by the AD collector ; Calibration of the influence of the nonlinear characteristics of the AD collector and the temperature drift of the constant current source includes: before the AD collector is not connected with the thermal resistance, connect the standard resistance box with the thermal resistance acquisition channel of the AD collector, and the standard resistance box The acquisition channel of the AD collector is calibrated, and the resistance value of the thermal resistance channel of the AD collector is calculated by the formula k2*(M/M0)+b2, where k2 and b2 are the calculation coefficients, and MO is the precision resistance collected by the AD collector The code value of the connection channel, M is the code value of the thermal resistance connection channel collected by the AD collector.

Further, the linear calibration of the acquisition channel of the AD collector goes through the following steps: S1. Control the operation of the AD collector, and set the standard resistance box resistance to R1, the AD collector acquisition code value Mz=M1; S2. Set the standard resistance box The resistance is R2, the AD collector collects the code value Mz=M2; S3. Determine the calculation coefficients K1 and b1 by the formula Rz=k1*Mz+b1: K1=(R2-R1)/(M2-M1); b=R1- (R2-R1)*M1/(M2-M1); get R=(R2-R1)/(M2-M1)*Mz+R1-(R2-R1)*M1/(M2-M1 through k1 and b1 ).

Further, the calibration of the influence of the nonlinear characteristics of the AD collector and the temperature drift of the constant current source includes: S4. Control the operation of the AD collector, and set the standard resistance box resistance to R1, the AD collector's acquisition code value M=M3; S5. Set the resistance of the standard resistance box to R2, the AD collector collects code value M=M4; S6. Calculate the coefficients k2 and b2 through the formula R=k2*(M/M0)+b2: k=(R2-R1)/(M2 /M0-M1/M0); b=R1-(R2-R1)*M1/(M2-M1); According to k2 and b2, we get R=(R2-R1)/(M2/M0-M1/M0)* (M/Mt)+R1-(R2-R1)*M1/(M2-M1); where M0 is the code value of the precision resistance channel.

The beneficial effects of the present invention: the method for improving the accuracy of the thermal resistance temperature transmitter of the present invention can effectively eliminate the temperature drift of the constant current source by connecting a precision resistor in series with the thermal resistance and the linear calibration of the AD collector. As well as the influence of the non-linear characteristics of the AD collector, the detection accuracy is greatly improved.

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