Liquid level detection circuit, device and calibration method thereof

Abstract

The invention discloses a liquid level detection circuit, a device and a calibration method thereof. The liquid level detection circuit comprises a voltage controlled oscillator, a phase discriminator, a judgment unit and a variable resistor unit, wherein the voltage controlled oscillator is respectively connected with two output terminals of a sampling needle and the variable resistor unit, and outputs a first signal to the phase discriminator, the phase discriminator receives the first signal and a reference signal, and respectively outputs control voltage relevant to the frequency difference value of the first signal and the reference signal to the voltage controlled oscillator and the judgment unit, the judgment unit outputs a control signal to the variable resistor unit according to the control voltage in the calibration state, and the variable resistor unit sets the self resistance value according to the control signal. The invention compensates the capacitance through regulating the resistance value of an oscillator resistor, and realizes the self calibration of the liquid level defection device, and the replacement of the sampling needle by customers is easier.

Description

【Technical field】 [0001] The invention relates to a sample adding system, in particular to a liquid level detection device in the sample adding system. 【Background technique】 [0002] In the medical field, it is often necessary to use a sample adding system to realize the sampling and adding of test samples and / or reaction liquids. In a liquid sampling system based on a sampling needle (such as a biochemical analyzer sampling system), the liquid level detection circuit often uses the detection principle of the equivalent capacitance change of the sampling needle to judge whether the sampling needle touches the liquid surface. During the production process of the sampling needle, there is a certain tolerance in its capacitance, which has a great influence on the performance of the liquid level detection circuit. Therefore, the liquid level detection circuit usually needs to be calibrated for the specific sampling needle. [0003] At present, the method for calibrating a spe...

AI Technical Summary

Problems solved by technology

However, this calibration method is cumbersome and inconvenient to adjust, especially when the customer needs to replace the sampling needle by himself.

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