Inside the case is a diaphragm capable of absolute pressure measurements, and a sealed and evacuated vacuum chamber is separated by a diaphragm from the vacuum pressure to be measured. This serves as the reference quantity.
With increasing evacuation, the difference between the pressure which is to be measured and the pressure within the reference chamber becomes less, causing the diaphragm to flex. This flexure may be transferred by mechanical means like a lever, for example, to a pointer scale.
The DIAVAC DV 1000 is made for rough pressure measurement in corrosive environments as the sensitive parts are in a sealed reference volume and the materials exposed to vacuum in the sensing cell are Stainless steel/FPM.
To increase the accuracy of the gauge: each scale is individually calibrated for optimum performance.