inductive displacement transducer

An LVDT is actually a specific type of inductive transducer that uses a three-coil arrangement to give a highly linear differential output. In practice, many people use the terms interchangeably. Kingmach offers both LVDT-style and simple half-bridge inductive probes. The half-bridge is lower cost and works well with our standard signal conditioners, while the full LVDT gives better temperature stability and is preferred for precision lab applications.

Yes, with the right sealing. Our standard sensors are IP68 rated for temporary immersion, but for permanent underwater use we add a welded pressure housing and use a cable with a molded jacket that can handle down to 100 meters depth. We also offer vented versions to equalize pressure and avoid cable wicking.

You want the expected displacement to stay within 80% of the sensor’s full range to avoid nonlinearity near the ends. For crack monitoring in a concrete dam, ±5 mm is typical. For a landslide inclinometer chain, you might need ±50 mm or more. Our team can review your project data and suggest a safe range, keeping in mind that over-ranging can damage the core stops.

Most Campbell data loggers read differential voltage easily. We match the transducer to a 2.5 V DC excitation and provide a ±2.5 V output, which you can wire directly to the analog input. For long cable runs, we recommend a 4-20 mA current loop with an external 12-24 V supply. We also have an interface box that converts the AC LVDT signal to a stable DC voltage if your logger lacks AC excitation.

Every sensor comes with a calibration sheet showing displacement versus output at several points, traceable to national standards. For most geotechnical monitoring, you can go 2-3 years between checks unless the sensor experiences a shock or extreme temperature cycle. We offer factory recalibration service and can supply a portable calibrator if you need to verify on site.