Liquid level thermocouple sensor signal circuit

In the development and application of liquid level thermocouple sensor, often will meet the required output of the transducer with the transmitter output is different, or the user of the existing transducer output cannot satisfy the new requirements, it is need to change the original output in the transmitter, in order to meet the needs of various customers, we have to have a variety of output of the transmitter. For example: as a type 2 tables, more than the standard output of 0 ~ 10 ma, or 0 ~ 10 v, and the application of three type table, it is 4 ~ 20 ma or 1 ~ 5 v, how to transform between them, is that we must solve the problem.

1.

the processing of temperature drift of the thermocouple sensor temperature drift can be divided into zero temperature drift and sensitivity temperature drift. Zero temperature drift of the thermocouple sensor is not compressed output drift caused by temperature change, the thermocouple sensor applications, often with a constant current power supply, zero and its temperature drift compensation methods available resistance series parallel method.

power supply bridge road thermocouple sensor, liquid level thermocouple temperature compensation sensor sensitivity is usually used in circuit. R of the Rt in the network for temperature coefficient and sensitivity temperature drift of synthetic thermal resistor, Rs, Rp and Rz as negligible resistance temperature coefficient, is used to adjust the temperature coefficient of Rt, via the above zero and sensitivity temperature compensation of thermocouple sensor output signal can be considered in a certain temperature range has nothing to do with the temperature change.

2, amplification and deal with the nonlinear

any force sensitive thermocouple sensor nonlinear size, plus or minus, signal processing and transmission to be linearized processing, liquid level makes the result was a signal of thermocouple sensor and a linear relationship with liquid level. Linear circuit is designed according to the size of the nonlinear and the positive and negative, linearization can be conducted in the different stages of signal processing, some in the analog signal phases, some in the digital signal phases.

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure thermocouple sensor, digital temperature thermocouple sensor