3
Section 4
Operation Basics
Digital Display
The three-digit display represents the real time vacuum pressure in inches of
mercury (inHg). Minimum vacuum equals 00.0 and the maximum vacuum
reading, depending on altitude, is approximately 30.9 inHg.
LED Indicators
The VAS - 4 has four LED indicators; High, Low, Latch and Polarity. See
Fig. 1 for their locations.
High LED Indicator
This LED indicates that the vacuum pressure exceeds the preset High Alarm
set point.
NOTE: This indicator is real time, i.e., it does not wait for the delay timer to
time out.
Low LED Indicator
This LED indicates that the vacuum pressure is below the preset Low Alarm
set point. This LED indicator is also real time.
Latch LED Indicator
When either the high or low indicators are active, this starts the delay timer.
If the alarm is active longer than the preset delay time, then the latch LED
indicator will become active. This indicator stays active until the manual reset
button (see Fig. 2) is pushed. This indicator implies that either an alarm has
occurred or is still active. If the latch indicator is on and the High/Low
indicators are off, then an alarm condition has occurred, but is not active now.
If either the High or Low indicators are active, then this represents that the
alarm condition is still active.
NOTE:
The High or Low alarm relays do not become active until the latch
alarm indicator is on.
Polarity LED Indicator
When this LED is on this indicates that the VAS - 4 is measuring
pressure. The digital display shows this pressure measurement in inches
of mercury (inHg). (1 inHg = 0.49 psi)