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Water Level Sensors: Everything You Need To Know

A recent study indicates that the global population at risk of flooding has increased since 2000. Thus, people in at-risk countries must have a water level detection system. Water level sensors are one of the most readily available and inexpensive tools for liquid level detection. Moreover, you can even purchase or create your IoT sensors to interface with your innovative technology. Nevertheless, this guide will explore what water level sensors are, why they're important and how you can integrate them into your daily life.


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What is a Water Level Sensor?


A water level sensor (AKA fluid or liquid level sensor) detects and measures the amount of liquid in a container, tank, or area. People unknowingly use technology that contains a water level sensor of some sort every day. For instance, the mechanism that measures and monitors your vehicle's fuel level utilizes a water/fluid/liquid level sensor. Thus, we can surmise that water level sensors assess liquid (water) levels in a container or area using this example.


brake fluid reservoir that uses a liquid level sensor

brake fluid reservoir that uses a liquid level sensor


We can also use them to alert us when a liquid reaches a certain level. Furthermore, water level sensors can also trigger an automatic response in machines. For instance, flash an indicator, or activate a drain or other water level controls when the liquid reaches a certain level.


How Does a Water Level Sensor Work?


There is a wide range of different types of water level sensors. However, all of them fall under two main classifications. They can either be point-level measurement sensors or continuous-level measurement sensors. Water level sensors that utilize point level measurement detect when a liquid is present at a specified point. Inversely, continuous-level measurement sensors display the constant level as it increases and falls.


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Types of Water Level Sensors


There are different types of water level sensors for each classification. This portion of the guide will cover how they work and which applications they suit the best. Additionally, we'll also talk about their limitations in certain use cases.


Types of Point Level Measurement Sensors


Capacitance Water Level Sensors


A capacitance sensor is a proximity sensor that emits an electrical field. It detects the liquid level by observing its effect on its electrical field. These sensors are small, inexpensive, accurate, and have no moving parts.

Most capacitance water level sensors consist of a long rod that you must submerge into the liquid. Furthermore, it would help if you calibrated them before using them. This task may be arduous for liquids in large containers. However, they are also invasive to the product. Moreover, they can only detect certain liquids, which is fine if you plan on using them for water detection. However, if you plan to use them to measure the level of corrosive chemicals, we would advise against that.  

Nevertheless, capacitance level sensors are suitable for liquid storage tanks. For instance, a water treatment facility would be the ideal application.


Water tanks that you can use capacitance water level sensors in  

Water tanks that you can use capacitance water level sensors in  


Optical Water Level Sensors


Optical level sensors function by converting light rays into electrical signals. They measure a physical portion of light then translate it into a perceivable measurement. Visual level water sensors have no moving parts. Furthermore, high pressure and temperature do not affect them. They do not need to touch the liquid they measure in some cases.

They are small in size, and we can use them in most liquid applications. However, they utilize a lens that's prone to get dirty. Thus, it requires cleaning and maintenance from time to time. Optical level water sensors are handy in run-dry conditions in fuel applications. For instance, you can use them to alert you when oil, coolant, or hydraulics are low in machinery.  


Conductivity (Resistance) Water Level Sensors


Conductivity level sensors use a probe to test the resistance or conductivity. This probe contains two electrodes that supply an alternating current to them. When a liquid covers the search, its electrodes form a part of an electrical circuit.

This process causes the current to flow. The current produces a signal indicating that the liquid level is either high (above a specified level) or low (beneath a specified level). As with the capacitance water level sensor, the conductivity level sensor contains no moving parts. Furthermore, they are also low-cost and relatively easy to use.

However, they are invasive and can only sense conductive liquids. Furthermore, their probes erode over time. It would help if you replaced them from time to time.


Vibrating (Tuning Fork) Water Level Sensors


Vibrating level sensors use a fork-shaped sensing element with dual tines. The part vibrates at its natural resonant frequency. As the container/tank level changes, so will the fork's frequency vibrates. This process allows the sensor to detect the level of water in a container/tank.


Tuning fork

Tuning fork


Vibrating water level sensors are cost-effective and compact. Additionally, they're easy to install and have a low maintenance level. Moreover, they have a large variety of liquid and material measurement applications. Mining, chemical processing, food, and beverage industries use these sensors for level detection.

However, (like most point-level sensors), they are invasive to the liquid and material they're measuring.


Float Switch Water Level Sensor


Image of modern aqua float switch

Image of modern aqua float switch


The float switch (or level transmitter float switch) uses a device that raises or lowers when liquid increases or decreases in a container/area. This process triggers the opening or closing of a circuit. Float switches are non-power devices that directly indicate the water level. Furthermore, they are inexpensive.

Unfortunately, they do come with a few disadvantages. For instance, they are invasive, contain moving parts, and are relatively large. Moreover, they will only indicate when water reaches its highest or lowest level. Hence, they cannot measure a variable group.

Despite this limitation, they are suitable for measuring the liquid level in large water tanks. Furthermore, we also use them in harsh environments such as lakes and dams. 


Types of Continuous Level Measurement Sensors


Ultrasonic Water Level Sensors


Ultrasonic water level sensor used in a water treatment plant

Ultrasonic water level sensor used in a water treatment plant

Source: Creative Commons


Ultrasonic sensors function by releasing and receiving ultrasonic waves (echolocation). The time the waves take to travel and return is how we measure distance. Ultrasonic water sensors are compact, contain no moving parts, and are reliable. However, they can be expensive and can sometimes harm the environment. 

Nevertheless, one of the most significant advantages of ultrasonic sensors is that they are non-invasive. They typically consist mainly of stainless steel and other corrosion-resistant material. As such, they require no contact with the liquid to measure it. Consequently, the properties of the fluid they measure do not affect them. Additionally, they are self-cleaning because of the vibrations they emit. 

A good application for these types of sensors is asphalt tanks in a shingle manufacturing plant. We can place the sensor on top of the tank away from the hot asphalt. The sensor would actuate a mechanism that fills the tank when the level of the asphalt gets low.


Radar (Microwave) Water Level Sensor


Radar water level sensors utilize antennas to transmit microwaves to a liquid. The liquid then reflects the microwaves to the tank. These waves are incomprehensibly fast, operating at the speed of light. The sensor uses the time between emission and reception of the signal to detect the level of the water/liquid.

Radar sensors are resistant to temperature, pressure, and dust. In addition to liquids, they can also measure pastes, powders, and solids. Furthermore, they give accurate water level measurements and do not require calibration. Moreover, it doesn't have to touch the liquid it is sensing. Thus, it is non-invasive.

Radar sensors are ideal for hot liquid storage tanks. However, as with most continuous level measurement sensors, radar level sensors are expensive. Moreover, they have a limited detection range. Therefore, we can also use them for hot asphalt tanks in shingle manufacturing plants.


Submersible Pressure Transducer (Transmitter)


Submersible pressure transducer sensors measure the amount of water in a tank/area by evaluating its pressure on them. We usually place them at the bottom of a site. Since we use these sensors in harsh environments, they must withstand excessive pressure. Thus, they must consist of rugged materials.

We use this water level instrument with other liquid level sensors as reference gauges, mainly when we utilize them for surface water applications. 


Water Level Sensor Module


Water sensor level module

Water sensor level module


We primarily use liquid water level sensors in commercial and industrial applications. However, some are available for educational and hobbyist purposes. The water level sensor module is one such type of sensor.

Water level sensor modules are typically minified conductivity liquid level sensors. They mainly use variable resistance to determine the amount of water in a container. They can also detect the size of water drops/droplets within an area/system. Thus, it's possible to use them to see precipitation or moisture in the air.

They are compatible with the most popular microcontrollers and single-board computers such as the Raspberry Pi and Arduino Uno. The sensor's body consists of ten exposed copper traces. Half are sense traces, while the rest are power traces.

Some water level sensor modules feature a power LED that indicates a current running through the module.


Interfacing A Water Level Sensor Module with an Arduino


Water level sensor module vector image

Water level sensor module vector image

Source: FreeSVG


The water level sensor module has a straightforward structure. It generally consists of three pins:

Signal (S): An analog pin that sends signals to the microcontroller/SBC to indicate the fluid level.

VCC/5V (+): The power input pin. It accepts a 3.3V to 5V input.

 GND (-): Indicates the ground connection.

 We can use these pins to interface the liquid water level sensor with the Arduino.


Water Level Sensor Model and Arduino Project Tutorial


Arduino Uno Connected to breadboard

Arduino Uno connected to the breadboard.


The following tutorial will show you how to connect the liquid water level sensor module to the Arduino and display water depth on an LCD screen. The LCD character display will act as our liquid level indicator. 


Tutorial Part List


You'll require a few components for this project. They include:

  • Arduino Uno (or any other compatible microcontroller)
  • Arduino Mega 2560
  • Water Level Sensor Module (or Leak Detection Sensor)
  • Breadboard and Wire Kit
  • LCD Character Display
  • 10K Potentiometer


Tutorial Steps


Arduino Uno next to display screen module

Arduino Uno next to display screen module


  1. Connect the water level sensor's ground pin to the ground pin on the Arduino.
    * Note: Alternatively, you can connect or route the connection through the ground pin on your breadboard
  2. Connect the VCC to the 5V rail on the Arduino (or breadboard)
  3. Connect the signal pin to any of the analog input pins on the Arduino – we suggest using the A5 pin
  4. Run the Arduino IDE on your computer, copy and flash the following sketch onto the Arduino

Note: Alternatively, you can use this sketch to print the water sensor's output onto the console

Ensure that you've correctly connected your LCD character display before following the above steps (if you have one). If you want to learn more about the LCD character display, you can visit our article on i2c adapters and protocols. Additionally, we also have a helpful guide on LCD interfaces.

Everybody's water is different and contains inconsistent impurities and chemicals. Thus, you'll need to adjust the code and calibrate the water level sensor to ensure it's returning accurate readings for your current water level. Nevertheless, once you've assembled your project, you can start calibrating it by testing it in a glass of water and changing some of the variables in the code.

There are many practical uses for this project. For instance, you can detect if your water heater leaks by searching for moisture in the drain pan.

However, once you've calibrated the water sensor correctly, you should see the depth level on your LCD screen or console.

Water heater with gas safety valve

Water heater with gas safety valve


You can also use it in empty vacation homes to assess water near the toilets or under sinks.   




Water level sensing technologies come in a variety of types. Their applications can often overlap. Thus, when selecting a water level sensor, you must identify the purpose of the measurement. Furthermore, it would help determine the temperature of the liquid you'll be measuring. As the above text proves, you do not necessarily have to purchase a commercial water level sensor. Using an inexpensive Arduino microcontroller paired with a water sensor module, you can create one of your own. You can visit our guide on Arduino circuit boards to learn more about them. 



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