Chapter Three: Overview Tri
Points
41
Trip Points
The 640 Series controller provides two trip points (Trip Point A and Trip Point B). Each trip
point operates independently and controls an open collector output that can be connected to an
external relay. Each trip point has an adjustment pot, a status LED, and a test jack. Refer to
Figure 13, page 33, for the location of the trip point adjustment pots and LEDs. The test jacks
are located on the side of the unit, as shown in Figure 4, page 18. Refer to
How To Adjust the
Trip Point Values,
page 46, for instructions on changing the trip point values.
Action of the Trip Points
The trip points can be turned on when the pressure is above or below the trip point value,
depending upon the location of jumpers on the Transducer board. The initial configuration is:
•
Trip Point A is set to trip high; it is on when the pressure is
above
the trip point (it is off
when the pressure is below the trip point value)
•
Trip Point B is set to trip low; it is on when the pressure is
below
the trip point (it is off
when the pressure is above the trip point value)
When on, the trip point is connected, through the collector of an NPN transistor, to power
ground. Refer to
Trip Point Specifications,
page 54, for the ratings. You can use the unit’s trip
point output (available on pins 13 and 14 of the I/O connector) for further process control.
To change the action of a trip point, refer to
How To Select the Trip Point Action,
page 47.
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