Wastewater or water treatment industries use submersible level sensors to detect the depth of the liquid. A submersible sensor provides highly accurate readings and can work regardless of the tank or vessel size. This characteristic of a submersible sensor offers an advantage over other types of sensors mounted on the side of the fluid vessel.
How does a submersible level sensor work?
The mechanism consists of a long cable attached to the sensing device lowered down to the bottom of the vessel. The sensor measures the hydrostatic pressure of the liquid which is affected by two factors: the height and density of the liquid. Hydrostatic pressure pertains to the pressure exerted by the liquid. When the liquid’s density remains constant, any change in pressure will result in a change in fluid level.
However, this working principle is not infinite because there are other factors which may affect how the sensor works. Atmospheric conditions such as barometric pressure also impact hydrostatic pressure. In applications where the sensor is exposed to atmospheric pressure, a submersible sensor comes equipped with additional venting. This venting compensates for the presence of atmospheric pressure; hence, maintaining the accuracy of readings.
Submersible sensors are particularly versatile because of their compact design and fabrication. Other common applications include pressure control in deep wells, hydrometry readings in seawater, and other waste and water treatment uses.
Checklist for choosing the right submersible sensor
One of the common challenges encountered by engineers is choosing the right sensor for the intended application. The following are considerations when finding the right submersible sensor:
- Pressure measurement range. Since submersible sensors essentially measure hydrostatic pressure, the first consideration is the sensor’s pressure range. The most sensible principle in choosing the right pressure range is to look for a sensor which matches the application’s range of pressure. Another principle used in choosing a submersible sensor is choosing a sensor with a pressure range that is higher than required by the intended application. There is an advantage to this especially when there are unexpected pressure bursts within the vessel.
- Type of pressure. There are two broad categories of pressure which are sealed and vented. Vented pressure means the atmospheric pressure is the reference point. Since atmospheric pressure is the reference point, elevation and barometric pressure no longer affect the sensor. In contrast, a sealed sensor uses a sealed reference point which the pressure is measured against. In turn, a sealed sensor is affected by changes in elevation or barometric pressure.
- Output. Submersible sensors come in a variety of output options. Choosing the right output configuration depends on whether you want a stand-alone unit or a sensor used together with a controller. In choosing an output type, make sure that the sensor output also matches the controller’s input requirements.
- Measurement accuracy. The accuracy of a submersible sensor affects its price point. The higher the accuracy required by the application, the more expensive the sensor.
Understanding the impact of each parameter is vital in choosing the right submersible sensor and avoids possible issues and operational problems.
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