31
937A Multi-Sensor System
Line Frequency – Switch 5
Set this switch to the line frequency in use to minimize noise pickup. This
switch does not affect the power supply.
Factory preset line frequency:
As requested
Cold Cathode Sensor Delay – Switch 6
When cold cathode sensors are turned on at high vacuum, the discharge
current does not start immediately. This delay prevents activation of the cold
cathode set point relays and updating the processed outputs until the delay
has expired. After the selected delay, the pressure may be reported as LO if
the cold cathode sensor has not started.
Factory preset cold cathode sensor delay:
3 sec
Configuration-Switch 7
This switch should only be on for conditions described in the application note
on
Configuration of Cold Cathode Modules for 929/A/937/A Controllers.
UCAL Enable/Disable
The rear panel
UCAL Enable/Disable switch locks out use of Atm and Zero
Calibration modes for all sensors except capacitance manometers.
Factory preset UCAL Enable/Disable: Disabled
RS-232/RS-485 Communications Module
(Optional)
The character format is 8 data bits (MSB always 0), 1 stop bit, and either
even or no parity.
Select a serial bit rate and protocol from the DIP switch bank
SW1 on the
RS-232/RS-485 module, as shown here.
1
Select RS-232 or RS-485 electrical interface with switches 6
and 7.
2
Select the logical protocol with switch 5 (multidrop, with
attention and address characters, or simple).
3
Select serial bit rate and partity with switches 1- 4.
With RS-485 communications, multiple controllers can be connected to a host
computer on a common cable. The multidrop protocol must be used. A unique
address is needed for each device. SW3 should be set to a binary code
representing the controller's address. The "$" (00100100B or 24H), or
"attention" character, always precedes the address and may not be used for
any other purpose. Recommended ASCII characters for addresses are 0
through 9 (30H-39H), A through Z (41H-5AH), and a through z (61H-7AH),
although any value from 0 to 127 (7FH) except "$" may be used.
S 5
60 Hz
Off
50 Hz
On
S 6
3 sec
Off
30 sec On
S 7
Off
Serial rate and protocol selection,
switches are set for bit rate 9600,
RS-485
Switch bank 1
RS-485 address character
selection, switches are set for
30H, ASCII 0
Switch bank 3
