Gas measuring and warning device with indicator tube through which gas to be tested is directed

摘要

A device and method for measuring the concentration of a gas carried in a medium such as air comprising, an indicator tube having material therein which progressively changes color along its length as it is exposed to the gas to be measured. A flow device is connected to the indicator tube for drawing or pushing the carrier with gas therethrough to cause the progressive change in color in the indicator tube material. A light barrier in the form of a light source and detector facing each other and on either side of the indicator tube is provided and mounted to slide along the axis of the indicator tube and in a direction of propagation of the progressive color change. A reference light barrier is provided in the area of the indicator tube which is not exposed to the progressive color change to produce a reference signal which is compared to a signal produced by the movable light barrier. A motor is connected to the slide mounting of the light barrier for moving it along the axis of the indicator tube and a control device is connected to the movable light barrier, the reference light barrier and the motor for maintaining the movable light barrier in the area of progressive color change which area corresponds to the concentration of the gas. An evaluator is connected to the control device for evaluating the moving position of the movable light barrier, which evaluation corresponds to the concentration of the gas. An indicator and a threshold detector may be connected in the evaluator for producing a reading corresponding to the concentration of the gas and for producing an alarm when the concentration of the gas falls below or rises above threshold values which are preselected.