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The transducer operates as a drag-force flow meter. A thin flexible membrane, oriented perpendicular to the direction of flow, and a fixed plate form a capacitor. The dynamic pressure generated by the fluid flow (density times velocity squared) deflects the membrane, thus varying the capacitance and the resonant frequency of an electronic circuit. The frequency variations are sampled by a microprocessor. In order to obtain the mass flow rate, the microprocessor corrects the signal for nonlinearities such as the laminar-turbulent transition and fluid density variations. Because the membrane stiffens with increasing deflection and because of the high sensor resolution the sensor operates over a wide range (turndown ratio 100:1) with a flow rate uncertainty of less than 1%. The membrane natural frequency being above 20 kHz, fast flow transients and pulsations do not distort the measurement.

This paper describes a nonintrusive transducer for the measurement of crankshaft torque and speed on internal-combustion engines. The transducer is added to an existing drive train without requiring drive train modifications. Two non-contacting encoder-magnetic pickup combinations detect the phase angle between the pulse trains, which is a measure of the engine torque. A digital circuit, which includes a microprocessor, samples and processes the raw torque data. The concept provides for stable transducer operation independent of motor speed and varying ambient temperatures. The results from experiments on an eight-cylinder Diesel engine demonstrate that crankshaft torque and speed variations are detected with high resolution and detail, permitting on-line diagnostics including fault detection on individual cylinders.