The signal circuit and temperature drift processing of liquid level sensor

In the development and application of liquid level sensors, it is often encountered that the display of the required transmitter is different from the display of the existing transmitter, or the display of the user's existing transmitter cannot meet the new requirements. The original display of the transmitter needs to be changed. In order to meet the needs of various customers, a variety of display transmitters are required. For example: as a second-type meter, the standard display is mostly 0-10mA, or 0-10V, while the currently used three-type meter is 4-20mA or 1-5V. How to change between them is what we must solve problem.　　

1. Disposal of temperature drift　　

The temperature drift of the sensor can be divided into zero temperature drift and sensitivity temperature drift. The zero point temperature drift is the drift caused by temperature changes when the sensor is not under pressure. In the sensor application, constant current power supply is often used. The zero point and its temperature drift compensation method can be used in series and parallel resistors.　　

The circuit that the sensor of the current power supply bridge circuit, liquid level sensor sensitivity temperature compensation usually adopts is shown as in Fig. 2. Among them, Rt in the network of R is the thermistor whose temperature coefficient is in the same direction as the temperature drift of sensitivity, and Rs, Rp, Rz are resistances with negligible temperature coefficient, which are used to adjust the temperature coefficient of Rt. After the above zero point and sensitivity The display signal of the temperature-compensated sensor can be regarded as independent of temperature changes within a certain temperature range.　　

2. Amplification and non-linear treatment　　

The non-linearity of any force sensor has magnitude, plus or minus. The signal processing and transmission must be linearized. The liquid level sensor makes the signal obtained after the * linear relationship with the liquid level. The linearization circuit is designed according to the magnitude and sign of the non-linearity. The linearization can be carried out in different stages of signal processing, some in the analog signal stage, and some in the digital signal stage.