Abstract: Ambiguous measurement results can be obtained in the measurement and indication of high concentrations obtained in air of combustible gases when employing the thermal effect principle. In order to prevent such ambiguities from arising, the measuring range is, in accordance with the invention, limited to the linear part of the characteristic curve of the measuring sensor and displayed digitally.

Abstract: An electronic circuit for processing measured values obtained from a vortex sequence produced by a Karman vortex path, wherein the ultrasonically sensed signals are processed both digitally in a first circuit branch for a computer and analogously in a second circuit branch for the connection of a two-channel continuous recorder. An adjustable frequency transforming arrangement is serially connected in the computer branch for balancing the circuit, and an additional frequency-voltage converter and and integrator are serially connected in the recorder branch along with a control logic circuit inserted between the two branches for starting the recorder after activation of the computer only when signals which can be evaluated are present.

Abstract: A device for monitoring and indicating the operational readiness of a gas-measuring instrument fitted with a built-in chargeable battery has visible luminescent diodes that emit different colors when energized and which are disposed in an electrical flip-flop circuit with rheostats for adjusting the switchover values of the circuit which is provided with a pair of input leads for connecting a chargeable battery to the circuit.

Abstract: A bridge circuit is provided for a gas-detecting instrument of the type using an electrically-heated resistance element or filament as a sensing element. In order to prevent use of the instrument during the warmup period after initial energization, a portion of the bridge is short-circuited for a predetermined time after energization. The short-circuiting means is preferably a transistor connected across one of the arms of the bridge and controlled by a flip-flop with suitable time-delay circuits for switching the flip-flop.