937B Controller Instruction Manual
pg. 34
4. Auto Zero
Use the UP or Down arrow keys to select a valid gauge for autozeroing the Pirani (PR) or
Convection Pirani (CP). Only cold or hot cathode sensors can be used as the zero reference.
The zero will be executed only when:
(1) The system pressure per the CC/HC is less than 1X10
-5
Torr (1x10
-6
Torr for the PR).
(2) The Convection Pirani (or PR) reading is lower than 1x10
-2
Torr.
Ensure that the Convection Pirani/PR and the reference auto-zero CC/HC sensor are
connected to the same chamber at all times.
5. Manual Zero
The Convection Pirani or Pirani sensor can be manually zeroed. To do this, select YES in the box
next to Manual Zero and then push ENTER. A small
U
will appear under the sensor identifier on
the main display. Ensure that the system pressure is less than1x10
-5
Torr (1x10
-6
Torr for PR)
before executing a Manual Zero. The Manual Zero function will abort if the overall offset is over
1x10
-2
Torr.
6. ATM Value
The entered value is used for the atmospheric reading of the Pirani/CP when an ATM Cal is
performed. The default value is 760 Torr. Recall that elevation and weather will affect local
atmospheric pressures.
7. ATM Cal
To perform an ATM Cal, after entering the ATM Value above, select YES in the box next to ATM
Cal and then push ENTER. The ATM Value will be used as the reference pressure for the ATM
reading. A small
U
will appear under the sensor identifier on the main display.
8. Relay
Each CP/Convectron/Pirani channel has two preassigned relays as shown below. The controller
auto-detects the correct relays corresponding to where the sensor module is installed.
Module location
A1
A2
B1
B2
C1
C2
Relay assigned
1 & 2
3 & 4
5 & 6
7 & 8
9 &10
11 & 12
9. Enable
There are three
‘ENABLE’ settings available for a relay:
•
SET: forces the relay to stay in the activated (closed) state regardless of pressure and set
point values
•
CLEAR: forces the relay to stay in the deactivated (open) state regardless of pressure and
set point values.
•
ENABLE: the relay status is determined by the pressure, set point value, and direction.