
946 Controller Instruction Manual
pg. 34
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 946 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
9. Enable
There are three ‘ENABLE’ settings available for a relay:
a. SET: forces the relay to stay in the activated (closed) state regardless of pressure and
set point values
b. CLEAR: forces the relay to stay in the deactivated (open) state regardless of pressure
and set point values.
c. ENABLE: the relay status is determined by the pressure, set point value, and direction.
10. DIR
DIR determines when the relay is activated. If ABOVE is selected, the relay will be activated
when the pressure is above (greater than) the set point. If BELOW is selected, the relay will be
activated when the pressure is below (less than) the set point. The default setting for DIR is
BELOW.
See Figure 8-1 and Section 8.2 for a more detailed description of the DIR setting.