A submersible water level sensor determines the level of liquid by measuring the hydrostatic pressure exerted by the liquid column above it.
Submersible level sensors are specifically designed to be placed directly into the liquid they are monitoring. They consist of a few key components working together:
Components
- Pressure Transducer: This is the core sensing element that converts pressure into an electrical signal.
- Electronic Circuit: This circuit processes the signal from the pressure transducer.
- Cable: This connects the sensor to a control unit or data logger, transmitting the processed signal and often providing power.
How it Measures Level
The sensor is submerged to the bottom of the tank or body of water. The liquid above the sensor exerts pressure, known as hydrostatic pressure, which increases with the depth of the liquid.
- The pressure transducer includes a sensing diaphragm.
- This diaphragm is designed to deflect slightly under the hydrostatic pressure of the liquid above it.
- The sensor measures this pressure by means of a piezoresistive or capacitance-based sensing diaphragm. A piezoresistive sensor changes electrical resistance when pressure is applied, while a capacitance-based sensor changes electrical capacitance.
- The degree of change in resistance or capacitance is directly proportional to the hydrostatic pressure, and therefore, to the level of the liquid.
Output Signal
The electronic circuit within the sensor processes the changes detected by the diaphragm and converts them into a standard output signal. Submersible level sensors typically output a 4-20mA signal that is proportional to the level of the liquid. This analog current signal can then be read by a control system, display, or data acquisition device to show the actual liquid level.
By measuring the pressure and converting it into a proportional electrical signal, the sensor provides an accurate, real-time indication of the liquid level.
