Inductive Frequency-Modulated Hydrostatic Level Sensor

Inductive frequency-modulated hydrostatic level sensors work by measuring the pressure of the water column above the sensor’s diaphragm. A change in water level compresses a sealed inductive mechanism, shifting the resonant frequency of an LC oscillator. That frequency is transmitted up the cable, so the surface readout only needs to count pulses. Since frequency doesn’t weaken over distance like a 4–20 mA current, cable runs of 300–500 meters are routine without signal boosters. Kingmach supplies these sensors with ceramic or stainless steel diaphragms, depending on the environment. The body is typically 316L stainless, with optional PTFE coating for aggressive water chemistry. A ventilated cable design equalizes atmospheric pressure automatically, so barometric changes don’t show up as water level errors. Standard measurement ranges start at a few meters of water column and go up to tens of meters, with accuracy typically within 0.1% of full scale. Because Kingmach handles final assembly and calibration in-house, custom ranges and cable lengths don’t add the lead time you might expect from a catalog product. In practice, the FM output simplifies logging. Many data loggers can measure frequency directly, or you can use a compact converter to get RS-485 or SDI-12. There’s no need for high-precision analog inputs at the datalogger, which cuts hardware cost on large monitoring networks. Installers appreciate that the sensor doesn’t require field calibration – the factory calibration data is stored in the sensor head or provided as a report, so swapping units takes minutes. Kingmach’s support team can walk you through wiring and data conversion if your telemetry setup is older. For new projects, they suggest a simple test: submerge the sensor in a deep bucket, log the frequency for a few days, and confirm the reading stays within the noise floor. It usually does.