Livonia, Mich.— Embedded Magnetic Domain (EMD) torque sensors, developed by Fast Technology, promise to ease torque measurement in shafts compared to complex strain-gage methods or those requiring specialized instrumentation. EMD technology is a non-contact method that combines magnetic induction and electronic processing to obtain direct torque readings in real time.

Fast's EMD torque sensing technique has three main elements. The torque-carrying shaft is conditioned with a permanent magnetic pattern and actually becomes part of the measurement system. (Shaft material must be magnetizable.) A detection head (sensor) measures changes in the shaft's magnetic field caused by the applied torque. Completing the system are proprietary electronic circuits (using an ASIC) that condition the sensor's signals to indicate magnitude and direction of torque transmitted by the shaft.

Standard EMD torque sensors measure torque up to 1,000 Nm (737 lb-ft) on shafts rotating as fast as 100,000 rpm, but the method is usable on stationary shafts as well. EMD works with air gaps of 0.5-10 mm (0.02-0.4 in.) between the shaft and detection head. Typical torque measurement accuracy is given as 0.5% of full-scale reading. Target applications include automotive, power tool, machine tool, and oil-production industries. www.fastechnology.com

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