101B - PAGE 5
1.0 GENERAL INFORMATION
This manual contains technical and general information concerning the installation, operation and calibration of Hastings
Compact Vacuum Gauges, VT-Models, and associated components.
For proper operation, Hastings Compact Vacuum Gauges must be suitably connected to a Hastings companion Gauge Tube.
Attempting to use this Vacuum Gauge with any other transducer may damage both the gauge and other transducer.
1.1 Description:
Hastings Compact Vacuum Gauges are self-contained instruments that offer extreme versatility for all vacuum applications. The
electronic design assures long life and minimal maintenance. Compact models are ready for mounting onto a panel. Cabinet
models are also available with or without switching attachments that can monitor 2 or up to 5 stations. The letter "A" in the
model number (i.e. Model VT-5A) designates 0-1 VDC analog output. See SELECTION CHART, page 3, for complete descriptions
and model numbers.
These instruments utilize Hastings rugged but sensitive gauge tubes which are designed specifically for each of the three
available ranges. Tubes are also compensated for temperature and rate of change of temperature.
1.2 Operating Principle:
Operation of the Hastings Vacuum Gauge
is based on a patented low voltage AC
bridge which heats a noble metal
thermopile circuit (Figure 1.1). A change
in pressure in the tube creates a change
in the thermal conductivity of the gas
cooling the thermopile, which in turn
causes a temperature shift of AC
thermocouples A and B. This causes the
DC output from the two thermocouples to
change with pressure.
The DC thermocouple, C, is unheated and
in series with the indicating meter circuit. Ambient temperature variations will develop voltages in all thermocouples; however,
the transient effects in heated and unheated elements are equal and opposite, therefore the unheated couple compensates for
transient temperature changes.
1.3 Specifications:
Range, all VT-4 Models................................................................................ 0-20 millimeters of mercury or 0-20 millibars
Range, all VT-5A Models................................................................................ 0-100 microns of mercury or 0-0.1 millibars
Range, all VT-6 Models....................................................................................... 0-1000 microns mercury or 0-1 millibars
Power .................................................................................................................... 115 VAC, 50/60 hz; 230 VAC optional
Output ....................................................................... VT-4A,VT-5A,&VT-6A Models, 0-1V @ 4 mA (1V @ Hard Vacuum)
Size........................................................................................................................................ See Dimensions, page 21
Cables ...................................................................... 6-foot power cable and 8-foot gauge tube cable (lengths are approx)
Weight ................................................................................................ Approx. 1-1/2 lb., including gauge tube and cable
FIG 1.1
