User's Manual

174-082010_Digital AVC Page 9 of 17
All THI gauge tubes are shipped with a protective cap or cover at the evacuation port to reduce
contamination and prevent damage to the internal thermopile elements. Once the protective cap or cover is
removed, a tube can be installed in any convenient position in the vacuum system without adversely
affecting calibration or performance. The recommended orientation is with the tube vertical and its stem
down. This will aide in preventing condensable materials from remaining in the gauge tube.
3.1 Quick Start
1. Install the appropriate DV4, DV5 or DV6 gauge tube (See the bottom of the instrument to determine
the appropriate tube) into the vacuum system. When installing the gage tube, consider the position
of the keyed octal plug so that the LED’s and controls on the DAVC will be readily accessible
2. Plug the gauge tube into the octal socket on the bottom of the Digital AVC.
3. Connect power common (-) to the blue wire (pin 4) and from +12 VDC to +30 VDC supply to the
green wire (pin 3). One of the LED's indicating over-pressure or under-pressure on the top of the
DAVC will illuminate.
4. While at one atmosphere, press the ATM button and release to set the atmosphere tube output for
this individual tube. The LEDS will flash while the button is pressed. Holding the button longer than
3 seconds will reset the adjustment back to the default value.
5. The low pressure accuracy can be improved if the vacuum chamber can be pumped down below the
minimum pressure range of the attached tube can be reached, adjust the HTR potentiometer until
that pressure reading is reported (See the serial communication section) or until the analog Pressure
Signal Output, pin 7 (yellow) equals approximately 1.0 Volts. Refer to Section 3.7 for more
information about tube calibration.
3.2 Analog Pressure Measurement
An analog Pressure Signal Output line, pin 7 (yellow), supplies a 0 to 1 VDC signal corresponding to the
output range of the selected tube. This signal should be measured with respect to the Analog Signal
Common line, pin 6 (violet). See the INSTALLATION section for a diagram showing the Analog Signal pin
out.
3.0 Vacuum Gauge Operation