`First` digital LVDT eliminates A-D converters

Schaevitz Sensors claims to have produced the world`s first self-contained LVDT (linear variable differential transformer) sensor with a digital output. The company says that the new device will eliminate the need for expensive, error-prone analogue-to-digital conversion, as well as avoiding complicated on-site set-up and calibration between the sensor and its control system.

The HC485 LVDT has an internal microprocessor which uses conversion tables to scale the analogue output into calibrated engineering units (mm or inches). It generates an output on a two-wire addressable RS 485 loop with a linearity claimed to be better than 0.25%. There are seven bipolar measurement ranges available from 2.5-150mm.

Schaevitz says that future versions will offer a linearity of 0.05% and will provide an increased stroke ability in a sensor of the same length by using linearity tables stored in the processor`s memory.

The sensor and its electronics are packaged in a tough, sealed, stainless steel housing. The device, which works off an 8.5-30V DC supply, is interchangeable with analogue LVDTs. Maximum and minimum values are stored on-board, and data from the sensors can be pasted directly into spreadsheets.