position sensors

Eddy-Current Principle
Magtrol Displacement Transducers use the principle of Eddy-current measurement. An aluminum tube moves along the transducer’s coil changing the induced Eddy-current losses, thus changing the coil impedance. An electronic circuitry housed in the transducer head, transforms the information of the measuring tube position into a linear signal. This circuitry uses modern SMD (surface-mounted device) technology, giving it robustness and reliability. The sensor is actively compensated for temperature changes.

Characteristics of the Output Signal
DI Series Displacement Transducers have a basic 3-wire configuration, providing a 4–20 mA current (20–4 mA for DI 63X models) proportional to the position of the aluminum tube. An indication of the temperature within the probe is also provided as a voltage output. In closed-loop systems, a specific piston position can be repeatedly achieved with a precision better than 0.05‰ full scale (i.e. better than 50 µm for a measuring range of 1 m).

Oscillating magnetic field created in the coil (4 kHz, up to 10 kHz depending on the measuring element and/or range) Eddy current generated in the aluminum tube Coil impedance increases when tube moves Measure of inductance variation Current remains constant Demodulated signal transformed into 4–20 mA