In this blog we will discuss different ways of measuring the level of water and other liquids. In the water business, containers are often used for temporary water storage. Wells or tanks are used for permanent storage. We will discuss various measuring techniques and compare the resulting data.
Measuring water level in a container using an ultrasonic sensor
You could measure the level of the water with different techniques, one being an ultrasonic water level sensor. If you have enough space at the top, installing an ultrasonic sensor gets you water level measurements with an accuracy of up to 1 mm (0,04 inch). One of the most renowned sensor manufacturers is MaxBotix (US) with their low-power ultrasonic MaxSonar product line-up.
Using pressure sensors for water level monitoring
Using pressure is another great idea if you have just limited space to install the sensor. You can either choose a submersible pressure sensor or just install a classic pressure sensor (like this pressure sensor from Honeywell) on the outside of a tank.
Submersible sensors are great because they require very little maintenance. Make sure however to choose a water level sensor that is suited for the liquid that is in the tank. The requirements for a diesel tank will be different from irrigation water. In the food business, or when you measure drinking water, make sure to ask for a proper certificate from the manufacturer. In many of these cases a titanium level sensor will be used.
Installing a pressure sensor on the outside of a tank will be cheaper in most cases, but of course your tank needs to have an opening on the bottom side in order for this to work.
Comparing ultrasonic and pressure sensor measurements
In this test, we used the LMP307 from BD Sensors (DE) and the MB7389 from MaxBotix (US). Both sensors were connected to Reporter, our wireless sensor module. We have the option to use a small solar panel as a power source, which is useful when you’re measuring in a remote location.
We installed these sensors in a container with a height of 200 cm, the pressure sensor on the bottom of the container and the ultrasonic sensor fixed on the upper side of the container pointing downwards.
The LMP307 from BD Sensors measures the distance between the bottom and the water surface while the MB7389 from MaxBotix measures the distance between the top of the container and the water surface.
The graph below shows the data of this experiment over a period of three days and with an interval of one minute. The water level has been decreasing slowly in this period, as indicated in the graph.
Both sensors can be used to measure the level of the water in a container or well. Which water level sensor is best suited for your project depends on two main factors. The first one is the environment you want to measure in and the type of liquid. The second factor is determined by the possibilities of installation. The ultrasonic sensor needs quite some space while submersible sensors can be used in a 30mm pipe. The ultrasonic sensor is known to be sensitive to obstructions like dirt or spider webs. Submersible sensors are slightly less accurate.
If you have a project coming up and you aren’t certain how to begin and which sensor to use, feel free to get in touch using the contact form.
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