Level Instrumentation: Transmitters, Switches and Indicators

A submerged sensor measures the pressure created by the liquid column above it. Because pressure is proportional to height times density, the transmitter converts it into a level reading, usually a 4–20 mA signal. It suits wells, sumps and open tanks. Accuracy depends on a known, stable density and, in vented applications, a proper atmospheric reference.

Use a switch when you only need to act at specific heights, such as stopping a pump on low level or raising a high-level alarm. Use a transmitter when you need the actual level for monitoring, stock control or analogue control. Many installations combine both, with switches as independent safety backup.

Only if the wetted materials are compatible. Water-grade sensors may use materials that corrode or swell in solvents, acids or alkalis. Tell us the exact chemical, concentration and temperature so that a suitable sensor material and, if needed, a different principle can be proposed. Plastic or coated parts may suit aggressive liquids where metals fail, but temperature limits differ, so confirm both together.

Please send the liquid, tank dimensions or measuring depth, open or closed vessel, temperature and pressure, required output, supply voltage and mounting preference. For borewells, mention depth and cable length. A photo of the existing installation also helps us match connections. Wiring length and whether a relay or 4–20 mA output is needed also help us confirm the right controller or transmitter.

It logs water level at set intervals, typically for borewells, reservoirs and observation wells. The data helps track drawdown and recharge, plan pumping and support reporting. It is a monitoring tool rather than a pump controller, so check whether you also need an automatic controller. If you also need pump control from the same tank, mention it so we can include a suitable controller.