The movement of the tip of a glass spoon gauge is followed by means of a linear variable differential transformer with a sensitivity of 2.2 mv. per micron. For a spoon that will stand a differential pressure of one atmosphere this amounts to 5 mv. per mm. of mercury. There is no hysteresis, the temperature coefficient is 0.1 mm. per °C, and there is a null point drift of about 0.05 mm. per hour. The over-all accuracy is 0.2 mm. in the range 0 to 760 mm.