Abstract: A method of detecting a component gas of a gaseous mixture, and apparatus implementing the method, is disclosed. The method includes passing the mixture through a fixed-phase separator to produce an effluent in which the components are consigned, in ordered [time-related] fashion, to predetermined portions of the effluent. That portion of the effluent containing the component gas to be detected is monitored to produce a measurement indicative of the quantity of the component gas in the mixture.

Abstract: Apparatus for processing a composite noise signal containing sonic and ultrasonic components generally in a frequency range of about 20 Hz-100 KHz to make audible both components of the signal includes a heterodyne circuit operable in response to a rectangular wave local oscillator signal to produce output signals which are within the frequency range of human hearing.

Abstract: A transducer unit comprised of a pair of transducers coupled together in a manner such that the offsets, drifts and the like of the circuit elements of one transducer are opposed by and cancelled out by the circuit elements of the other transducer. The transducers can be in the form of Wheatstone bridges and each of the branches of the bridge contains a circuit element of each transducer, respectively, the circuit elements of the branches of the transducer unit being in opposition to each other so as to cancel out the effects due to temperature, acceleration, aging and the like.

Abstract: A sensor for use on the front end of a flexible, resilient probe for use in an underground duct of the type which contains one or more current-carrying cables. The sensor is provided with a signal generating device for detecting a particular operating condition of a cable in the duct when the sensor moves through the duct adjacent to the cable. In one embodiment of the sensor, acoustical signals are sensed by a crystal when such acoustical signals originate from a leak in the pressurized sheath surrounding the cable. In another embodiment of the sensor, a coil senses the magnetic field surrounding the cable so that electrical shorts occurring in the cable can be monitored. In a third embodiment of the sensor, a heat detector is provided so that the sensor can detect hot spots in a duct.

Abstract: A circuit having a transducer which normally provides a non-linear output as a function of a stimulus to which the transducer is responsive. The circuit is provided with a feedback resistor from at least one of a pair of output terminals coupled to the transducer, and the feedback resistor is coupled to the power input of the transducer. Any change in the output voltage will cause a current change through the transducer, and this current change has a linearizing effect on the output voltage. The circuit is especially adapted for use with a Wheatstone bridge having a power amplifier coupled to the input thereof and a differential amplifier coupled to the output thereof. In such a case, a pair of feedback resistors couple the output terminals of the differential amplifier with the input terminals of the power amplifier.

Abstract: A differential amplifier suitable for use with a transducer network, such as a Wheatstone bridge, for measuring small signal voltages while eliminating common mode voltage contributions applied to the input of the amplifier. A potentiometer is connected across the output terminals of a pair of amplifiers whose positive input terminals receive the common mode voltage components and induced signal voltages from the transducer network. The shiftable terminal of the potentiometer is connected to the negative input terminals of one of the two amplifiers and adjusted to control the gain of the amplifier pair. The output signals of the differential amplifier are proportional to the induced signal voltages and devoid of the common mode voltage.

Abstract: A duct probe having a coaxial cable is provided to advance a microphone through an underground or other duct containing a cable in a pressurized sheath for sensing fluid leaks in the sheath. The coaxial cable is embedded in a resilient fiberglass rod of one-piece construction. The rod is sufficiently flexible so that it can be wound onto and unwound from a reel having a cage-like configuration. A stationary base is provided to rotatably mount the reel, and the base is provided with a length measuring device responsive to the movement of the duct probe as it is unwound from the reel so that the distance by which the duct probe penetrates a duct can be determined. At the outer end of the rod, a microphone is mounted for sensing the sounds caused by a fluid leak in the pressurized sheath in the duct.

Abstract: A method and apparatus for remotely monitoring air leakage in communication cables is disclosed. Improved volume flow meters are remotely attached at the air inlet to manhole mounted manifolds for supply of dehumidified air to telephone cables. Dehumidified air passes through the remote meters into the manifolds and then interior of a sheath of a communication cable wherein the discrete conduits can be kept dry and under air pressure. The remote volume flow meter at each manifold includes a diaphragm having an air flow conduit mounted in movable opposition to a variable area orifice. The diaphragm actuates a variable resistor, which preferably includes a tailored neutral density wedge. This tailored neutral density wedge moves with the diaphragm towards and away from a position between a light source (typically a light-emitting diode) and a photo sensor (typically of the photo resistor variety).