REFERENCE PRESSURE DEVICES FOR CALIBRATING PRESSURE-MEASURINGINSTRUMENTS

摘要

A differential-pressure transmitter having a range diaphragm and a slack diaphragm to receive process pressures and to apply such pressures to an interior sealed chamber containing a fill-liquid. A vertically-oriented tube containing liquid communicating with the instrument fill-liquid contains a ball movable by gravity down through the liquid to create a reference-pressure pulse directed to the range diaphragm to provide for checking instrument performance. A relatively large weight is suspended from the ball to increase the effect of gravity on the ball, so as to increase the magnitude of the reference-pressure pulse. A flexible seal-and-pivot connection is provided at the top of the tube to permit substantial inclinations of the instrument relative to vertical without interference with the wall of the tube. The additional weight is in one embodiment divided into vertically-separable segments to provide for successive bottoming of the segments as the weight descends, to provide a stepped pressure pulse. Errors due to change in static pressure are avoided or reduced by special compensating arrangements.