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Manual: 153-082010_HPM 4-6 Vacuum Gauge Page 7 of 12
Operation of the Hastings gauge sensor (DV-4 or DV-6) is based on a low voltage AC bridge
that heats a noble metal thermopile. A change in pressure in the gauge tube alters the molecular
collision rate and therefore the thermal conduction of the gas or gas mixture surrounding the
thermopile. This causes a temperature shift in the AC heated thermocouples A and B (Fig. 3-1).
The resultant temperature shift causes a change in the DC output from couples A and B (which
varies inversely with pressure). Thermocouple C provides compensation for transient changes in
ambient temperature.
4.1. Sensor Electrical Connector
The thermocouple vacuum sensor tube interfaces with the HPM 4/6 Vacuum Gauge via the
octal connector. The Octal connector is “keyed” so that proper connection is assured. Always grip
the connector by its cover and not the cable when plugging or unplugging the connector.
Disconnecting gauge tube by pulling on the cable may result in damage to the octal socket
and/or cable.
4.2. Pressure Measurements
The HPM 4/6 is shipped from the factory fully calibrated, and will provide immediate and
accurate pressure measurements.
1. Plug octal socket on to DV4 or DV6 thermocouple tube.
2. Turn unit on by positioning the slide switch on the side on of instrument case to DV-4 or
DV-6 position as required depending on which thermocouple tube is being monitored. The
DV4 or DV6 switch position indicators are labeled on the bottom of the unit. Once the slide
switch is in the proper position, the display will indicate one of the following:
a. The correct pressure. (Value within range of sensor selected).
b. Pressure over range “1”, where the sensor is at a pressure greater than full scale or the
sensor not connected.
4.0 General Information