Messeinrichtung zur Bestimmung der Konzentration von Gasen und Daempfen

摘要

The measuring system is used esp. to determine methane content in coal mines and has a concentration indicator connected in parallel with a branch of the bridge. An alarm unit emits a signal when a critical concentration value is exceeded. An A.C. generator is connected in series with the D.C. voltage source and a phase sensitive A.C. amplifier is connected in parallel with the other branch of the bridge. The A.C. component of the bridge detuning current is applied to the input of the A.C. amplifier to switch it to transmitting or stopping operation. The output of the amplifier is connected to the alarm unit.