MKS 651C, Instruction Manual, Page: 69 / 172

Chapter Five: Local Operation How To Set a Process Limit Relay
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How To Set a Process Limit Relay
There are two process limit (PLO) relays in the 651 controller. Each relay has two trip limits: a
high trip limit, and a low trip limit. Refer to Table 10, page 34, for the I/O connector pinout to
determine which pins are for relay 1, and which are for relay 2. Use the appropriate pins to
configure the relays for normally-open or normally-closed operation.
While the pressure remains within PLO limits, the 651 pressure controller actuates the relay (a
normally-open contact closes, and a normally-closed contact opens). The 651 pressure controller
de-actuates the relay (a normally-open contact opens, and a normally-closed contact closes)
when the pressure crosses:
•
above the high trip point
or
•
below the low trip point
How To View and Adjust a Process Limit Relay
1. Scroll to process limit 1.
PROCESS LIMIT 1
HIGH 50.0 mTorr
2. Select the desired pressure value for the high trip point of process limit 1.
3. Scroll to the next display.
PROCESS LIMIT 1
LOW 30.0 mTorr
4. Select the desired pressure value for the low trip point of process limit 1.
5. Scroll through the menu selections in the manner just described, to set the desired pressure
values for process limit 2, high and low trip points.
How To Disable a Process Limit Relay
To disable a high limit trip point, set it to full scale.
To disable a low limit trip point, set it to negative full scale.