Piezoelectric variable-frequency contact type liquid level switch

Abstract

A piezoelectric variable-frequency contact type liquid level switch belongs to the field of liquid level detection switches, and comprises a tube, wherein a probe support is arranged at one end of the tube, the piezoelectric variable-frequency contact type liquid level switch is characterized in that the probe support is fixedly provided with a piezoelectric ceramic sheet and a thermosensitive resistor which are respectively connected and arranged in a circuit board in the tube by leads, the circuit board is provided with a power circuit, an oscillating circuit, a frequency-voltage conversion circuit, an amplifying circuit, an isolating circuit and a driving circuit which are connected in sequence electrically, the oscillating circuit is connected with the piezoelectric ceramic sheet, and the thermosensitive resistor is arranged on the frequency-voltage conversion circuit. The thermosensitive resistor can also be connected to the amplifying circuit for temperature compensation. The circuit board is simple in structure, fewer for parts, low in material cost, and less in expending of working time; after one-time corresponding arrangement is conducted, the piezoelectric variable-frequency contact type liquid level switch has the advantages of being low in cost, maintenance-free, high in property, long in service life, good in universality, wide in application range and large in measurement range.

Description

technical field [0001] The invention provides a piezoelectric frequency conversion contact type liquid level switch, which belongs to the field of liquid level detection switches and can be widely used in fixed-point liquid level measurement of various liquid media such as water, oil, weak acid and alkali, and impurities. It can be used as a frost sensor for refrigerators or other occasions that can cause significant changes in the frequency of the probe. Background technique [0002] Currently used liquid level switches are float type, tuning fork type, capacitive type, pressure type and ultrasonic type. The most widely used is the float type, and the more advanced ones are the tuning fork type and the ultrasonic type, but the float type liquid level switch is bulky, and the accuracy of controlling the liquid level is the worst. Because it completely uses mechanical moving parts, it is easy to be stuck. And the lifespan is not long. The tuning fork type liquid level switc...

AI Technical Summary

Problems solved by technology

The most widely used is the float type, and the more advanced ones are the tuning fork type and the ultrasonic type, but the float type liquid level switch is bulky, and the accuracy of controlling the liquid level is the worst. Because it completely uses mechanical moving parts, it is easy to be stuck. and not long life

The tuning fork type liquid level switch adopts a U-shaped tuning fork vibration structure. When the vibration frequency and amplitude of the tuning fork are changed by the damping effect of the surrounding medium, the liquid level is detected according to this frequency change. It has high sensitivity and is relatively stable. Due to the limitations in terms of its volume, the tuning fork is easily affected by sundries and malfunctions, and it is expensive.

Ultrasonic type can realize non-contact detection and has strong adaptability, but the price is too expensive, and it is only suitable for use in places with relatively harsh conditions

[0003] Existing liquid level switches either have poor performance or very good performance, but the cost is too high and the price is too expensive, or the scope of application is very narrow. There is no low-cost, high-performance, long-life, and relatively general liquid fixed-point detection switch device.

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