A multi-point liquid level detection circuit

Abstract

The invention discloses a multipoint liquid level detection circuit which comprises a partial pressure resistor, a resistance circuit formed by connecting N resistors in series, and N transistors corresponding to various series connection nodes of the resistance circuit. N is a positive integer; a certain incidence relation exists between the resistance valve Rm of the resistor of the mth series connection node of the resistance circuit and the resistance valve R0 of the partial pressure resistor. The collector of each transistor is connected to the corresponding series connection node of the resistance circuit, the emitter of each transistor is connected with an earth terminal, bases are connected with an exploring electrode, and a first power supply terminal can be electrically connected with the exploring electrode through liquid. According to the liquid level detection circuit, insulating materials are adopted to seal all circuits except the exploring electrode, the first power supply terminal and a liquid level voltage output end. The multipoint liquid level detection circuit can detect liquid levels of multiple detection points, and has the advantages of being flexible in designing, low in cost, simple in structure and high in accuracy.

Description

technical field [0001] The invention relates to the technical field of position detection, in particular to a multi-point liquid level detection circuit. Background technique [0002] In daily household appliances, many aspects involve the detection of liquid level, such as water dispenser. In practical applications, in order to effectively prevent the liquid in the device from being boiled dry, it is often necessary to detect the liquid level. [0003] The prior art provides a capacitive or resistive liquid level sensor, the former uses the relationship between the capacitance and the depth of the two poles of the capacitor immersed in the liquid, and uses the change of the capacitance to convert the liquid level into the high and low level of the electrical signal; the latter Or use a resistor made of a material with a large temperature coefficient of resistivity, and apply a voltage across it to detect the change of the liquid level. As the energization time changes, the...

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Problems solved by technology

[0004] The defect of the above two technical solutions is that: the former utilizes the basic charging and discharging properties of the capacitor, that is, the capacitance of the capacitor changes with the process of charging and discharging, and uses the change of the capacitance to detect the change of the liquid level; The change of capacitor capacitance requires a certain charge and discharge time, and a small amount of liquid level change will not cause a huge difference in capacitance. Therefore, the technical solution of the capacitor has the defects of hysteresis and low sensitivity, and the detected liquid level position does not Inaccurate; the latter uses the characteristic that the temperature of the resistor changes with the change of the power-on time for liquid level detection, because the temperature of the resistor is a parameter that is difficult to accurately control in actual operation, and the temperature of the resistor needs to be adjusted later. The conversion circuit that converts the temperature value into the liquid level position becomes very complicated, and it has electrical requirements for electronic devices, such as sensitivity, so there are also defects of circuit complexity and high cost

The defect of this scheme is that since the sliding resistor is installed in the automobile reducer, limited by the height and space inside the reducer, the sliding arm of the sliding resistor is very short, and the sliding distance is generally 20-30mm (millimeters), and the coil of the sliding resistor There are only tens to more than one hundred turns, so a certain change in liquid capacity corresponds to fewer turns of the moving coil, and the resolution is low

Moreover, the position of the float also occupies the space volume of the container carrying the liquid, so it is only suitable for the liquid level measurement of the container with a large space

[0006] In the current solution, there is also a technical solution that uses the difference in the position of the liquid level to cause the change of the air pressure inside the container. These existing technical solutions all have the defects of complex structure and high cost, and the existing technology fails to realize In fact, it is necessary to detect multiple liquid level positions, that is, liquid level detection with multiple detection points cannot be realized

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