Abstract: Apparatus for determining or measuring the depth of precipitation accumulating on the surface of a pathway, such as an airport runway or the like. The apparatus includes a sensor having electrical transducer means for emitting and sensing ultrasonic energy and having a body of material adapted to be embedded in the pathway with the top surface of the body being substantially flush therewith and exposed to the precipitation, the transducer means being physically coupled to the body. A circuit causes the transducer means to emit pulses of ultrasonic energy which are reflected as a plurality of reflections from the top surface of the body and from the upper surface of an accumulation of precipitation on the top surface of the body and are respectively returned to the transducer means which in response to the reflected pulses produces corresponding electrical signals.

Abstract: Apparatus for zone refining rods of semiconductive material is disclosed including an RF induction work coil having a single turn lying in a plane generally transverse to the lengthwise axis of the rod and encircling the rod. The coil is part of an RF power oscillator circuit including a power amplifying device (e.g. a vacuum tube) having a control electrode and a power output electrode, the latter being connected through a voltage-blocking capacitance to an input node of an inductive-capacitive tank circuit. The tank circuit includes the work coil and a capacitance. One input side of the work coil is connected in a circuit to the input node capacitance being connected between the input node and the other input side of the work coil. A grounded center tap of the coil serves as a ground node of the tank circuit.The disclosure includes a circuit arrangement for supplying a signal of preselected magnitude to the control electrode for forcing the amplifying device toward desirable operating conditions.

Abstract: Apparatus for detecting wet and icy conditions on the surface of a pathway. A block of electrically insulative material is embedded in a pathway with the top surface of the block being substantially flush with the surface of the pathway and exposed to atmospheric precipitation. A sensor electrode is positioned a predetermined distance beneath the top surface of the block and encapsulated in the block so that the accumulation of atmospheric precipitation on the top surface of the block affects the capacitance and conductance between the sensor electrode and the pathway. A time-varying electrical current having an amplitude which is substantially constant and independent of the accumulation of atmospheric precipitation on the top surface of the block is supplied to the sensor electrode. The apparatus also includes an amplifier for amplifying an electrical signal applied to a pair of input terminals thereof.