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Page 31
Set Point Operation
The Terranova® 752A can be utilized for process control functions through the use of two
programmable set points and corresponding relays. Each channel is able to independently-operate
one set point (i.e. CHANNEL 1 SET POINT and CHANNEL 2 SET POINT). Set point pressure values
may be adjusted via the front panel or through serial communication. Relay output is accessible
via the MISC I/O or AUXILIARY I/O connector for CHANNEL 1 and the AUXILIARY I/O connector
for CHANNEL 2. See
on page 6 and
on page 7 for relay pin configuration.
Figure 11.
Relay operation graph
The corresponding relay will activate once the pressure reading is less than or equal to the
respective SET POINT value. The corresponding SET POINT LED will become illuminated once
the relay is active. The relay will deactivate once the pressure reading is greater than or equal to
20% of the respective SET POINT value. For example, if the SET POINT is 1.0 × 10
-8
Torr, the relay
will activate once the pressure reading is less than or equal to 1.0 × 10
-8
Torr and deactivate once
the pressure reading is greater than or equal to 1.2 × 10
-8
Torr. If the set point value is OFF, the
relay will be disabled. The set point pressure display resolution is in 0.1 increments per pressure
decade (or order of magnitude) in torr units. Display resolution is converted from torr to millibar
or Pascal units. See the
"Appendix: Note on set point relays"
for relay use with inductive or
capacitive load switching.
