Honeywell Elac Nautik Gmbh

Karl-Ernst Biehl

Egon Tyssen

Jorg Boscher

Conrad G Von Roedern

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.

Method and apparatus for determining the charging of charcoal filters

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 collector current dependent on the grid frequency, digitizing and storing the measured collector current in a memory as a function of the frequency, storing in a further memory a table of collector current/frequency curves for different gases, comparing the measured curves with the stored curves and, if a measured curve is identical with one of the stored curves, producing an indication signal characterizing the gas corresponding to the particular stored curve. An apparatus for measuring a gas concentration is provided using this method.

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Hanau, Germany

Karl-Ernst Biehl