MKS 640A/641A, Manual, Page: 59 / 88

How To Adjust the Trip Point Values Chapter Four: Operation
46
How To Adjust the Trip Point Values
Equipment required: a digital volt meter (DVM)
Caution
Only qualified individuals should perform the installation and any
user adjustments. They must comply with all the necessary ESD and
handling precautions while installing and adjusting the instrument.
Proper handling is essential when working with all highly sensitive
precision electronic instruments.
Each trip point has a test jack that allows you to measure the trip point setting. The test jacks are
located on the side of the unit. Figure 4, page 18, shows the location of the test jacks and a
ground connection. The trip point adjustment pots, located on the top of the unit, allow you to
vary the trip point setting.
The range of the trip point setting is 0 to 5 Volts, corresponding to 0 to 100% of transducer full
scale.
Note
The trip point range is from 0 to 5 Volts, regardless of the range of the set
point input and pressure output signals.
1. Insert the positive test probe into the test jack labeled “TP A” and the ground probe into
the test jack labeled “Gnd.”
Insert the probes sufficiently to obtain a good reading. There is no back plane in the test
jacks to stop the probe.
2. Use a small screwdriver to adjust the trip point adjustment pot labeled “TP A”.
Refer to Figure 13, page 33, for the location of the trip point adjustment pots. Turning
the pot clockwise raises the trip point setting.
3. Repeat steps 1 and 2 to adjust TP B.
Refer to How To Select the Trip Point Action, page 47, to change the action of the trip points.