I am looking at an old Pressure Sensor with a dial display (shows Psi & inch hg gauge) on one end and a membrane type transducer on the other end. On the display there is a label that says "Nr:4" I wonder if this refers to the chemical inside this sealed sensor assembly. Does anyone know what "Nr:4" means? Generally what chemical do they use in these older dial type mechanical pressure sensor?
15 years ago