This is a non-contact liquid level sensor with status indicator and adjustable sensitivity. It is especially suitable for detecting liquid level of all sorts of non-metal small diameter pipes(outer diameter D≤10MM). The status feedback of the sensor can be given in real-time. Besides that, the sensor comes with a 4pin sensor adaptor that can directly collect digital signal, convenient for connecting with Arduino or other main-controllers. This liquid level sensor can be widely used in liquid detection of water dispenser, small pipes, and perfusion tubes.

This non-contact liquid level sensor is developed on advanced signal process technology by high-speed signal processing chip. It can measure the liquid level of a closed container without the influence of container wall thickness, and will not be affected by corrosive liquids like strong acid and alkali, or other impurities.

Working Principle

A Non-contact liquid level sensor is used for detecting whether there is liquid by water induction capacitor. When there is no liquid approaching the sensor, there will be some certain static capacitance to ground on the sensor due to the presence of distributed capacitance. When the liquid level rises slowly to approach the sensor, the liquid parasitic capacitor will be coupled to the static capacitance so that the final capacitance value will increase. The changed capacitance signal will be input to the control IC for signal conversion, by which to transform the changed capacitance value into the variation of certain electric signal. Then the degree of the variation can be detected and determined through specific algorithms. When the variation exceeds a threshold value, it means the liquid level reaches the sensing point.


Board Overview

Board Overview

Num Label Description
1(Left, Brown) VOUT Liquid Sensor Power Positive, +5V~+24V
2(Left, Blue) GND Liquid Sensor Power Negative
3(Left, Black) IO1 Liquid Sensor Forward/Backward output select
4(Left, Yellow) IO2 Liquid Sensor Level Signal Output
1(Right, Red) VIN Power Positive
2(Right, Black) GND Power Negative
3(Right, Blue) IO1 Liquid Sensor Forward/Backward output select
4(Right, Green) IO2 Liquid Level Signal Output




Pipe Installation


  1. The product is suitable for pipe with outter diameter 3~10mm. Diameter over 11 cannot be used with this sensor.
  2. The spring plate cannot be bent over 60°.

Sensitivity Adjustment

Sensitivity Adjustment

Connection Diagram

Connection Diagram

Sample Code

 * @File  DFRobot_Level_Sensor.ino
 * @brief  Detecting the liquid level of non-metallic containers,and check the status of sensor through serial port
 * @copyright  Copyright (c) 2010 DFRobot Co.Ltd (
 * @licence  The MIT License (MIT)
 * @author  [liunian](
 * @version  V1.0
 * @date  2020-08-13
int inPin = 8;
boolean running = 0;//when running=1, the liquid is detected, print out 1, otherwise, print out 0; running=0, the liquid is detected, print out 0, otherwise, print out 1.
int modePin = 9;

void setup()
  pinMode(inPin, INPUT);
  pinMode(modePin, OUTPUT);
  digitalWrite(modePin, running);

void loop()


  1. The liquid level sensor doesn't work when powered on (the indicator keeps off when the liquid level reached the sensing point, and it has no response to the sensitivity adjustment.).
    1) The sensor may not be in a good connection with the power source, please check the power connection.
    2) The power cable may be reversely connected, please check it.
    3) The power module is broken, change the power module and try again.
    4) The sensitivity may be too low, increase the sensitivity to a suitbale value.

  2. The indicator keeps on all the time.
    1) The sensitivity is too high, please adjust it to a suitabe value.
    2) The init parameter is revised abnormally, in this case the sensor needs to be returned to the factory for restarting init.
    3) There are impurities or other metal objects contacted with the sensor closely, please clean the sensor and keep it away from any metal objects.

For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

More Documents

DFshopping_car1.png Get Small Pipe Diameter Level Sensor from DFRobot Store or DFRobot Distributor.

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