937B Controller Instruction Manual
pg. 31
4. Factory Default
When YES is selected and entered for Factory Default, any Manual Zero data is removed.
5. Auto Zero
This selects a sensor for autozeroing of the capacitance manometer. Suitable sensors and their
channels are autodetected. NA which can be selected if Auto Zero is not required.
The Auto Zero will be executed only when:
(1) System pressure is less than 10
-5
xP
FS
(5 decades lower than the full scale)
(2) The CM reading is between 5x10
-4
xP
FS
and 0.05xP
FS
(0.05% to 5% of the full scale)
When a Capacitance Manometer has been zeroed, a U will be displayed under the gauge type
indicator (CM) of the zeroed channel to indicate this.
Table 6-1 shows the valid gauges that can be used for autozeroing based on the full-scale rating
of the capacitance manometer.
Full scale of CM
CP
PR
CC
HC
1000 Torr
Yes
Yes
Yes
Yes
100 Torr
No
Yes
Yes
Yes
20 Torr
No
No
Yes
Yes
Table 6-1 Valid Gauges for Autozeroing Capacitance Manometers
The Capacitance Manometer and the reference auto-zero sensor must be connected
to the same chamber at all times.
6. Manual Zero
This allows for manual zeroing of the CM from the front panel. To perform a manual zero,
highlight the ‘NO’ in the box after Manual Zero, and then change to ‘YES’ with the up/down keys
and push ENTER. The indicator will
change to ‘NO’, but a U will be displayed under the gauge
type indicator (CM) to indicate that it is user zeroed.
For accurate zeroing, the system pressure must be less than 10-5xP
FS
(5 decades less than the
full scale). The Manual Zero function will abort if the overall offset is greater than 5% of the full-
scale.
7. Operation Voltage
The operation voltage from the 937B is fixed at +/-15 Volts. This limits the selection of
capacitance manometers to only those req/-15 Volts operating power.
8. Relay
Each capacitance manometer channel has two preassigned relays as shown below. The
controller auto-detects the correct relays corresponding to where the sensor module is installed.
Sensor location
A1
A2
B1
B2
C1
C2
Relay assigned
1 & 2
3 & 4
5 & 6
7 & 8
9 &10
11 & 12