Pressure-balanced fused quartz Bourdon tube sensors work on precisely the same theory but takes advantage of the reflection of a beam of sunshine from the mirror to sense the angular displacement and latest is applied to electromagnets to balance the force on the tube and bring the angular displacem

Previously the instrument was renowned for demanding some skill and know-how to employ accurately. For prime precision measurements a variety of corrections has to be used as well as the ball should be spun in a pressure very well beneath the supposed measurement pressure for five hours just before