For direct indication of pressure differences between two sources (pressure drops infilters etc.).
An obvious advantage is the extremely simple construction with only one measuring system (Bourdon-tube, “1”).
The high pressure side is connected directly to the Bourdon-tube, while the low pressure side is connected to a diaphragm“2”.
The pressure is transmitted from the diaphragm via the liquid filling of the case to the exterior of the Bourdon-tube.
The resultant displacement of the Bourdontube indicates the pressure difference,which is then transmitted to the pointer “3” via a usual rack and pinion movement.
Accuracy +2.5% of FSD.