The HPM 4/6 is a lightweight control unit that operates with a standard 9 volt battery. The display is available to show units in Torr or mbar. The HPM 4 / 6 can be calibrated to an individual sensor or set for average sensor output to work for many different sensors of the same type. It is switchable to offer display for both the DV-6 (0.0001 to 1 Torr) and the DV-4 (0.01 to 20 Torr) sensors with out re-calibrating.