Series 642
OPERATION
605593EC
Edition 2017-11-24
79/113
5.5.1
Pressure control operation with 2 sensors
[applicable with 642 . . - . . . Q - . . . . version only]
If 2 sensor operation is enabled, changeover between the sensors is done automatically during pressure
control. For configuration refer to chapter «Setup procedure». We recommend a ratio of 10:1 between the
pressure gauges. Max. ratio is 100:1. High range respectively low range pressure gauge may be either
connected to sensor 1 or sensor 2 input. It’s required to do correct sensor configuration.
Between 90 and 100% of the low range sensor full scale, the low range sensor is phased out while high
range sensor is phased in during pressure rise. During pressure decrease the high range sensor is
phased out while low range sensor is phased in. This maintains a functional response behavior in case of
small calibration errors between the two sensors. The PRESSURE output in this range is a blend
between both sensors.
For monitoring purpose each sensor signal may be read out individually. Refer to «Explicit messaging
inquiry commands SENSOR 1 READING and SENSOR 2 READING».
Make sure that both sensors are calibrated. Do not close optional gauge isolation
valves during the transition phase between the sensors.
0
-1
0
V
High range
sensor
Low range
sensor
0
-1
0
V
SENSOR 1 READING
0 – 10’000
100 mTorr
1 Torr
0 mTorr
SENSOR 2 READING
0 – 10’000
PRESSURE
0 – 10’000
