Magnetostrictive sensors that use line-of-flight technology to determine a cylinder’s position are not especially rugged, and resistive potentiometers often lack the necessary resolution or operational life. Durable ME and MR linear sensors from Alliance Sensors Group, Moorestown, N.J., mount the same as time-of-flight and resistive sensors but do not require magnets, making them more rugged. They both use established eddy-current technology on the cylinder rod. These sensors are also contactless so there is nothing to wear out, unlike the sliding contacts in resistive potentiometers.

The MR sensor mounts in an SAE-8 port in the cylinder’s end cap. The ME sensor gets embedded in the end cap. Both devices operate at temperatures from –40 to 105°C, and pressures to 5,000 psig. They can measure strokes from 4 to 36 in., and resolution is 0.05% of full scale. The sensors’ short response times mean that cylinder speed is not an issue. They both feature SenSet, the manufacturer’s proprietary method of letting users match the sensor’s output to the cylinder’s exact range of motion after the sensor is installed. The manufacturer offers several cable and MS connector options.