Segmented liquid level sensor based on capacitance-to-digital conversion technology

Abstract

The invention discloses a segmented liquid level sensor based on the capacitance-to-digital conversion technology. A seven-segment sensor inner pole cylinder is a copper foil electrode bonded onto bakelite. An outer pole cylinder is a stainless steel sensor shell, the copper foil electrode is connected with a waterproof sensor junction box through a lead, the copper foil electrode is sleeved with a polytetrafluoroethylene insulation layer, an aviation plug is arranged on one side of the waterproof sensor junction box, and the top of the waterproof sensor junction box is provided with a sensor upper cover. According to the segmented liquid level sensor, a capacitance-to-digital conversion technology chip PCAPO1 is used in the capacitance detection method, the problem of stray capacitance of capacitance measurement is solved, the problem of measurement of multiple sections of capacitance at the same time is solved, compensation calibration can be performed on the stray capacitance in the chip through a circuit and an algorithm, and the compensation result is that gain offset within a proper temperature range can be achieved. Exchange between data and a host can be performed conveniently through an SPI or IIC data serial interface. The segmented liquid level sensor is low in noise, low in power consumption and simple in peripheral circuit, and microminiaturization and integration can be achieved easily.

Description

technical field [0001] The invention relates to the technical field of sensors, in particular to a segmented liquid level sensor based on capacitance-to-digital conversion technology. Background technique [0002] The measurement circuit of the capacitive liquid level sensor is a very critical part, and the capacitance change is very small due to the change of the liquid level, and the measurement range varies from tens of picofarads to hundreds of picofarads, so the key to the measurement circuit is the tiny The detection of capacitance and the measurement method of tiny capacitance can be divided into the following methods according to its measurement principle: [0003] (1) Resonance method The resonance method is to connect a fixed inductance L in parallel at both ends of the measured capacitor Cx (often accompanied by a leakage resistance Rx), and then add a variable frequency power supply. Adjust the frequency of the signal source to make the circuit resonate. At res...

AI Technical Summary

Problems solved by technology

Disadvantages are: not suitable for automation; not suitable for online measurement

The main disadvantage is: no automatic balancing measures

[0009] The charging and discharging method is the method adopted by the current mainstream liquid level sensor. The disadvantage is that it is interfered by parasitic capacitance.

[0013] At present, there is no mature experience and technology in the design of the interface circuit of the capacitive liquid level sensor in China.

However, the traditional measurement circuit built with discrete components such as resistors and capacitors has its insurmountable limitations.

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