Abstract: A trace gas detector including in a closed gas loop, two baffle cells with an intermediate trace gas filter, each baffle cell consists of an ionization source, a labyrinth-like recombination zone and a collector electrode. A differential circuit derives a differential signal from output signals of the two baffle cells, the differential signal depending only on the trace gas concentration. Temperature changes and supply voltage changes are compensated by means of the differential circuit.

Abstract: In order to distinguish useful electrical signals from noise signals which are superimposed on the useful signals, a time window is moved along the receiver signal by means of a shift register. If within this time window the received signal exceeds a predetermined minimum level for a predetermined period of time, this receiver signal is recognized as being a useful signal.

Abstract: An omnidirectional acoustic transducer achieves a broadband radiation or reception pattern with high efficiency by using several transducer rings located side-by-side with each ring comprising a plurality of radially directed individual transducer elements. The transducer elements in each of the rings are tuned to a particular natural frequency and are designed accordingly. Within each ring the transducer elements are energized in phase with one another. The natural frequency of the individual transducer elements differs from one ring to the other.

Abstract: For increasing the bandwidth of an electroacoustic omnidirectional transducer a piezoceramic tube is provided at its outer circumference with segment-shaped additional mass members having a larger outer surface area than the piezoceramic tube.

Abstract: For determining the charging of a charcoal filter with gases and vapors the acoustical and the electrical impedance of the charcoal layer are measured. The more the filter is charged the greater will be the density of the charcoal layer and therewith its acoustical conductivity. The charging of a charcoal layer with water vapor results in an increase of the acoustical as well as of the electrical conductivity. By comparing the acoustical impedance and the electrical impedance respectively of a partially charged charcoal layer with the impedance of a non-charged charcoal layer and by subsequent comparison of the impedance changes caused by such charging the influence of water vapor can be eliminated. A signal is generated corresponding to the charging of the charcoal filter with other vapors and gases which signal may be used for indicating the condition of the filter and for generating an alarm if the filter becomes exhausted.

Abstract: A method for detecting very small concentrations of gases in gas mixtures passed as a gas stream through a measuring cell having a chamber through which the gas stream flows through, a drift zone provided between an inlet and an outlet of the chamber, a gas stream ionizing radiation source located at the inlet of the drift zone, a collector electrode located at the outlet of the drift zone, a grid consisting of two groups of parallel wires located in the drift zone current adjacent grid wires are supplied with different electrical voltages and whereat an AC voltage of adjustable frequency is fed to the two groups of grid wires, and a measuring apparatus for detecting the collector current, including the steps of inducing the movement of the ions through the drift zone by means of a ventilator which generates a controlled gas flow to the collector electrode, periodically changing the frequency of the AC voltage applied to the groups of grid wires either continuously or stepwise, simultaneously measuring the co

Abstract: Echo-sounding apparatus with circuitry for achieving enhanced recording on electrically sensitive paper is disclosed in which the gain of a variable gain amplifier is reduced exponentially depending on the input signal amplitude as soon as this amplitude exceeds a predetermined level. The signal generated by the variable gain amplifier is supplied to low pass and high pass filters which are connected to two inputs of a differential amplifier which controls the recording element.

Abstract: Apparatus for remotely controlling the horizontal and vertical direction of a pendulously suspended transducer by means of concentric generally vertical control shafts is disclosed. A frame in which the transducer is mounted for rotation about a tilt axis is pendulously suspended from one control shaft. The other control shaft is rotatably coupled through a universal joint to a first pulley mounted in the frame for rotation about a vertical axis. The first pulley is rotatably coupled to a second pulley mounted on the transducer for rotation therewith about the tilt axis by means of a cable routed over guide pulleys which change cable direction.