Abstract: An agricultural machine having a machine element supported by and movable relatively to a wheel-supported main frame with power means for moving it up and down relatively in small incremental steps, to vary the distance to ground level. The distance to ground is determined and electrical signals corresponding to the distance generated. A control circuit receives the signals and provides "up" and "down" pulses. A monitor-controller circuit receives the "up" and "down" pulses and transmits them to the power means for actuating an incremental step up or down for each pulse.

Abstract: A distance-determining detector and method. A piezoelectric ultrasonic transceiver sends out pulses and receives their reflection and produces an analog output and a trigger output. The analog output is given effect only when it exceeds a threshold level, as shown by a comparator. The trigger output is used for disabling detection during transmission of the transmitter pulse and for producing a time interval during which the analog output is valid, when enabled. An AND gate is connected to the comparator and to the enabled trigger output. Clock pulses are counted, and a flip-flop circuit is connected to the counter and to the output from the AND gate. A multiplying digital-to-analog converter is connected to the flip-flop circuit for determining the distance. There may also be temperature compensation and scaling for the converter for validating the output thereof over a wide range of temperatures.

Abstract: Method and apparatus for determining the distance from a preselected point to a target. An electrostatic ultrasonic transducer in a special protective housing is used with a single-pulse, square-wave transmitter to compare a main signal with a calibration signal. A warning signal indicates when the number of signals actually received during each one hundred signals sent drops below a predetermined percentage. Noise is minimized by careful spacing and shaping of the calibration bar and by insulating foam in the housing.