Gas detection system

Claim 2

A gas detector system comprising: a. a gas leak detector sensitive to a particular gaseous substance to be detected, b. a gas sampling probe through which a sample gas is drawn, c. a source of diluent gas to which the detector does not respond, d. conduit means connected to supply sample gas from said probe and diluent gas from said source to said detector, e. a detector sensitivity control having a plurality of control positions, f. valve means responsive to actuation of the sensitivity control from one operative position to another to alter the relative flow rates of the sample gas and the diluent gas through said conduit means in a discrete step and thereby change the ratio of sample gas to diluent gas reaching the detector; and g. a bypass conduit arranged to bypass a portion of the gas flow from the probe around the gas detector so as to maintain the total gas flow through the detector relatively constant when the sensitivity control is activated to different control positions.

Claim 3

The gas detector system of claim 1 wherein the bypass conduit includes a calibrated orifice and valve means actuated by the sensitivity control.

Claim 4

The gas detector system of claim 1 including additional conduit means connected in parallel with the conduit means supplying sample gas from the probe to the detector, said additional conduit means having valves controlling the flow of gas therethrough which are operated in sequence when the sensitivity control is moved to different operative control positions.

Claim 5

The gas detector system of claim 3 wherein the additional conduit means have calibrated orifices of progressively different sizes.

Claim 6

In a gas detector system, a. a gas detector sensitive to a particular gaseous substance to be detected, said detector producing an electrical output signal variable in accordance with the concentration of said gaseous substance in the detector, b. a meter connected in a signal circuit to be actuated in accordance with the magnitude of said output signal, c. a gas sampling probe through which a sample gas is drawn, d. a source of diluent gas to which the detector does not respond, e. conduit means for supplying sample gas and diluent gas from said probe and source to said detector, f. sample attenuating means for altering the ratio of sample gas to diluent gas supplied to the detector, g. signal attenuating means for altering the ratio of the signal supplied to the meter to the total output signal of the detector; and h. sensitivity control means connected to actuate jointly the sample attenuating means and the signal attenuating means to vary the sensitivity of the detector over an extended range of operation.

Claim 7

In a gas detector system, a. a gas detector sensitive to a particular gaseous substance to be detected, said detector producing an electrical output signal variable in accordance with the concentration of said gaseous substance in the detector, b. a meter connected in a signal circuit to be actuated in accordance with the magnitude of said output signal, c. a gas sampling probe through which a sample gas is drawn, d. a source of diluent gas to which the detector does not respond, e. conduit means for supplying sample gas and diluent gas from said probe and source to said detector, f. sample attenuating means for altering the ratio of sample gas to diluent gas supplied to the detector, g. signal attenuating means for altering the ratio of the signal supplied to the meter to the total output signal of the detector; and h. sensitivity control means connected to actuate jointly the sample attenuating means and the signal attenuating means to vary the sensitivity of the detector over an extended range of operation.

Claim 8

A gas detection system of claim 5 wherein the gas detector is a halogen sensitive type and the source of diluent gas is air from which any halogen containing substance has been removed by filtration.

Claim 9

The gas detection system of claim 5 wherein the sample attenuating means and signal attenuating means operate in discrete steps of progressive attenuation magnitude.

Claim 10

The gas detection system of claim 7 wherein the signal attenuating means operates through a plurality of steps of progressive attenuation magnitude for each step change of the sample attenuation means.

Claim 11

The gas detection system of claim 5 in which the sample attenuation means comprises valves and calibrated orifices in the conduit means supplying gas to the detector, the valves being actuated in a predetermined sequence by the sensitivity control.

Claim 12

The gas detection system of claim 9 in which the sample attenuation means includes electrically actuated valves and a rotary switch connected to actuate the valves.

Claim 13

The gas detection system of claim 10 wherein the signal attenuation means comprises a rotary switch connected to resistance taps of a voltage divider in the signal circuit.

Claim 14

The gas detection system of claim 11 wherein the rotary switches controlling the signal and sample attenuating means are ganged to be rotated in unison by the sensitivity control means.