Abstract: A controller for maintaining a motor operation at a desired rotational speed utilizes a phase locked loop that receives input signals from a tachometer coupled to the motor shaft. Reference frequencies for the phase locked loop are generated by a voltage control oscillator in response to voltages selected in accordance with the desired motor speed. These selected voltages are coupled to the motor speed control to establish a motor speed within the lock-in range of the phase locked loop. Tachometric feedback is applied in parallel for the phase locked loop. The open loop drive provided by the selected voltage guarantees degraded open loop control of the motor should the control circuit fall.

Abstract: In a flow meter of the traveling wave type having a flexible undulating membrane, velocity detecting means is utilized to determine the velocity of propagation of the traveling wave associated with the undulating flexible membrane between at least two known locations on the flexible membrane. The velocity of propagation is proportional to the volumetric flow rate of fluid through the flow meter.

Abstract: The indirect measurement of the absolute volume of grain which does not fall through the chaffer sieve of a combine harvester and is discharged out the rear of the combine is calculated from the output signals provided by a matrix of sensors which are disposed about the cleaning sieve and which are capable of detecting the precipitating grain flow.