D395-90-880 Issue E
Page 14
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OPERATION
adjusted as one number from -10 to +6. When the ENTER key (
) is pressed after adjusting the exponent, the
complete number will be entered and the new threshold will become effective.
For each set-point, or link threshold, the low threshold must always be lower than or equal to the high threshold. If
you enter a low threshold which is higher than the high threshold (or vice versa), then both thresholds will be set to
the value that you have just entered.
If you set the high and low thresholds to the same value then there will be no hysteresis, and the relay may switch
on and off several times as the pressure changes through the set-point threshold. It is recommended that some
hysteresis is always used.
Note:
The set-point or link thresholds can be set to any value in the range 1.0 x 10
-10
to 9.9 x 10
6
. If you set the
thresholds to a pressure which cannot be measured by the gauge which you are using, then the set-points
or link will not operate.
4.5.3
Set-point 2 controlling gauge
The set-point 2 relay can be controlled by gauge 1 or gauge 2. To select which gauge is controlling the relay, first
select the menu option using the UP and DOWN keys ( / ). When this option is selected, the numeric display will
be blank and the SP2 LED will be lit. Either the G1 or G2 LED will flash to show the currently selected controlling
gauge. To change between gauge 1 and gauge 2, press the ENTER key (
). When the required controlling gauge
is flashing, press the UP or DOWN key ( / ) to move to a different menu option.
4.5.4
Gauge calibration
If gauge 1 or gauge 2 is a type which supports remote calibration (for example APG-X or WRG) then the calibration
options will be available. To calibrate gauge 1, select G1 and CAL LEDs together using the UP and DOWN keys
( / ), and then press the ENTER key (
). The message "CAL'd" will be displayed for 3 seconds to show that the
calibration command has been sent to the gauge. To calibrate gauge 2, first select G2 and CAL LED's.
Where an ASG is used, the calibration functions as a zero offset adjustment. You can cancel the calibration by
pressing the ENTER key (
) again. The message "OFF" will be displayed to confirm that the offset adjustment has
been removed.
Please refer to the instruction manual of the specific gauge which you are using for details of the correct calibration
procedure.
4.5.5
Units selection
You can change the pressure units for the display by selecting the units menu option. When this option is selected,
the numeric display will be blank, and the currently selected units will flash. To change the units, press the ENTER
key (
). The units enunciator will move between mbar, Torr and Pa with each press of ENTER. A further press of
the ENTER key (
) will select voltage mode, when the LED enunciators will extinguish and '0.000' will flash on the
display. Pressing ENTER key (
) again will return to mbar. When the required units are flashing, press the UP or
DOWN keys ( / ) to move to a different menu option.
When the units are changed, the set-point values will be converted to the new units. For example, if a set-point
threshold is entered as 1.0 x10
-3
mbar and the units are changed to Torr, then the value will be displayed as
7.5 x 10
-4
Torr.
