Means for calibrating pressure switches at extra-low pressure settings

摘要

A simplified calibration mechanism is provided for a pressure switch using an adjustable, spring-biased plunger arrangement for controlling the trip force and hence the pressure to which the switch responds. The mechanism includes an especially configured lever pivoted at one end, contacting an especially shaped cam as a follower at its other end and the plunger at its mid portion. First calibration means are provided in the lever's pivoted end to adjust the normal low-high pressure settings of the switch. Second calibration means are provided to isolate the lever and cam from the plunger for effecting a precise setting of the pressure switch at extra-low pressures.