Capacitive Liquid Level Sensor Review

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Hi everyone, this is a review of the capacitive liquid level sensor from DFRobot (Type: WKC1204-N/P-FL).

When it comes to liquid level sensors, I guess most of you may feel unfamiliar with them, but actually, they play a vital role in our daily life.

Liquid level sensors are usually designed to monitor, maintain, and measure liquid levels. With the rapid development of related technology, they have been used for a variety of industrial, agricultural, and consumer applications, including liquid-level sensing in transport tanks or storage tanks, fuel level detecting, and monitoring washing machines, steam irons, etc.

Today, many such sensors can also detect adhesive substances such as glue and ink in addition to common liquids, for example, the one I'll test here. Unlike general ones, this capacitive liquid level sensor can detect high-viscosity and low-corrosive liquids, such as glue, lubricating oil, grease, ink, engine oil, powder and other special materials.


It determines whether there is liquid and distinguishes between liquids by detecting the capacitance of the liquid.

And the sensitivity of the sensor can be adjusted by the knob (clockwise to increase, counterclockwise to decrease) to adapt to more media.


It's compatible with 12~24V power supply; the brown wire is connected to positive voltage and the blue wire to the ground. Meanwhile, it features an indicator light to feedback sensor status in real time; the indicator changes when liquid is or isn't detected are shown in the figure below.


Now, I will test this sensor with water, lubricating oil, ink, glue, powder and rubbing alcohol.

When the sensor is powered on, the indicator shows red light; put it into the container with liquid, when the probe touches the liquid, the sensor senses it and the built-in indicator will show green light; then take the sensor out of the container, when the probe leaves the liquid surface, the sensor doesn't sense the liquid and the indicator will show red light.


In particular, glue is highly viscous and has the highest viscosity among these liquids, so at this point, the sensitivity of the sensor is crucial to the test.


The sensor can detect low-corrosive powder such as flour.


This liquid level sensor adopts a conical head of anti-hanging-liquid design to reduce the phenomenon of hanging liquid in detection.

When there are liquid residues, foam, scabs, etc. in the probe part, we can also adjust its sensitivity to avoid false signals.  


With temperature compensation, it can detect stably in the range of -25℃~75℃. These detailed designs ensure the stability of detection performance to a large extent.


Next we test the sensor's operating status at low temperature: 


Test environment: constant-temperature oven

Ambient temperature for the test: -18℃~-20℃

Tested liquid: rubbing alcohol

Place the container with rubbing alcohol into constant-temperature oven, then put the liquid level sensor into the container, and set the temperature of the oven to -20℃, and test time to 7 hours. During the test, I'll regularly check the working status of the sensor; after 7 hours of testing, it turns out that the liquid level sensor can work normally for a long time at low temperature of -18℃~-20℃.

Then we test its operating status at high temperature:


Device for the test: microcomputer-controlled heating table

Tested liquid: water

Temperature of the tested liquid: 70℃~74℃

Place the container with hot water on the heating table, then put the liquid level sensor and a high temperature sensor into the container. The high temperature sensor allows us to monitor the temperature changes in real time when connecting the 1602 RGB LCD display module to it. During the test, I'll regularly check the working status of the sensor; after 8 hours of testing, it turns out that the liquid level sensor can work normally for a long time at high temperature of 70℃~74℃.

But for the test, we should note that:

1. We need to wipe up the probe after detecting high-viscosity liquid, otherwise the sensor accuracy will be affected by the liquid (like glue) stuck to the probe when it's solidified.

2.The measuring temperature of the sensor should keep in the range of -20℃~75 ℃.

3.The sensor can't be under pressure of over 0.3Mpa.

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