MKS 937B Operation Manual
56
8 Connecting Relay and Analog Outputs
8.1 Connecting 937B relay outputs
There are twelve relays available in the 937B controller. These can be used to control the operation of
devices (such as valves) associated with a vacuum system. Relays can be accessed through the 25 pin
D-Sub connector on the back of the AIP module.
Relays used in the 937B are normally open (NO) SPDT relays. Thus if no is supplied to the controller, no
output signal can be sent. During the 937B power up process, a delay circuit is implemented to ensure
that all of these relays are disabled (i.e. maintained in the normally open state) until reliable control
signals are available.
If normally closed relay outputs are required, an external conversion is required.
Currently, relay activations are determined using the main microprocessor in the 937B. The time required
to process a measured pressure signal therefore results in a relay activation time delay of between 50 to
100 msec.
Analog comparators that facilitate reduced relay response times will be added in future to ensure short
relay response time (less than 5 msec). The main microprocessor will then be used only for setting the
reference values for the comparators.
8.1.1 Pin out for the 937B relay output
Table 8-1 identifies the pins for the male, 25-pin "D" connector on the AIO/Power module that provides
the connection to the relay output. 12 relays are built into the controller and 4 relays are assigned to each
sensor module. If a single sensor module such as a CCG or a HCG is present, all four of these relays are
assigned to the module. If a dual sensor module such as a Pirani, CP, or capacitance manometer is used,
2 relays are assigned to each sensor connected to the module.
Pin Description Pin Description
1 Relay 1 NO 14 Relay 7 NO
2 Relay 1 Common 15 Relay 7 Common
3 Relay 2 NO 16 Relay 8 NO
4 Relay 2 Common 17 Relay 8 Common
5 Relay 3 NO 18 Relay 9 NO
6 Relay 3 Common 19 Relay 9 Common
7 Relay 4 NO 20 Relay 10 NO
8 Relay 4 Common 21 Relay 10 Common
9 Relay 5 NO 22 Relay 11 NO
10 Relay 5 Common 23 Relay 11 Common
11 Relay 6 NO 24 Relay 12 NO
12 Relay 6 Common 25 Relay 12 Common
13 No Connection
Table 8-1 Pin out for the 937B relay output.