An instrument for automatic calibration of baroswitches

Abstract

 The equipment described in this paper consists of an environmental testing chamber and an automatic manometer coupled to several servo-controlled recorders for the mass calibration of baro switches used in audio-frequency modulated radiosondes. A differential transformer with a soft iron float as its core follows the level of mercury in the manometer tube as the pressure falls or rises in the chamber. The chart drive in the recorders is synchronised with the motion of the differential transformer through servo links. When the aneroid pen moves over the commutator and makes a contact on a conducting segment, the recorder pen is deflected and the resulting trace indicates the pressure on the pre-printed chart. The pressure values corresponding to each contact are thus automatically recorded.