Many water wells range in depth from 10 to 60 feet, while others are up to 100 feet. So when a customer needs a water level sensor in these deep wells, the experts at Automation Products Group, Inc. (APG) recommend our submersible pressure transducer, the PT-500. Submersible pressure transducers are a favorite in the water and wastewater industries. These level sensors are inexpensive, versatile, and easy to install.
How This Water Level Sensor Works
The submersible pressure transducer rests at the bottom of a tank or well, and measures level by detecting the pressure exerted by the volume of liquid above it. This is converted to a level based on the dimensions of the tank or well, and the specific gravity of the liquid being measured. In this case, the specific gravity is 1 since the liquid is water.
The level reading is produced as the PT-500 level sensor sends a 4-20mA signal to the controller. The two endpoints on the 4-20mA scale have to be calibrated to give an accurate measurement. This is done by setting 4mA to 0 psi and 20mA to the maximum psi.
Calibrating For Well Depth
Let’s say you have a well with a water depth of 100 feet. You need the signal to output 20mA at 100 ft. However, since the sensor measures pressure in PSI, you’ll need to convert the pressure to level. You’ll do this by multiplying the water depth in inches by the inches of water to PSI ratio of .036063. The conversion is as follows:
100 ft. X 12 in. = 1200 in.
1200 in. X .036063 = 43.276 PSI
We’ll calibrate the sensor so that when it reads 43.276 PSI, it signals an output of 20 mA. This translates to a water level of 100 ft. Our PT-500 submersible pressure transducer can have a maximum pressure range of 200 PSI, which means they are capable of measuring depths over 450 feet.
Cable Length
It can take a while before water is reached when drilling a well. This is why some wells are so deep. So when installing deep well water level sensors, you may need a very long cable. We have built some of our PT-500 sensors with cable lengths well over 1500 feet. This isn’t an issue for the signal since a 4-20 mA signal is being used. Amplified signals can travel cable lengths well over a few thousand feet.
However, it does mean that the cable must be supported by a high tensile strength wire. This can be attached directly to the PT-500 submersible pressure transducer’s housing and used to raise and lower it into the well.
If you have any questions on measuring well water levels, let us know. Send a email or make a phone call. Our measurement experts will be happy to help you!
WRITTEN BY
Sami T.
Sami Thompson is APG’s Marketing Technical Writer and has been with the company since 2022. With a master’s degree in English from Utah State University and a 40-page thesis publication under her belt, Sami has a demonstrated strong writing background. In her free time, Sami enjoys reading and birdwatching.