VAT 651 Series - Operation with 2 Sensors

OPERATION
Series
651
66/99 Edition 2014-07-10 605451EC
5.5.1 Operation with 2 sensors
[applicable with 612 . . - . . . E - . . . . 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. It is required that the high range pressure gauge is connected to
sensor 1 input and the low range pressure gauge to the sensor 2 input.
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. 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.
Make sure that both sensors are calibrated. Do not close optional gauge isolation
valves during the transition phase between the sensors.
Example of PRESSURE and SENSOR READING allocation:
Above picture shows a 2 sensor system. In this configuration sensor 2 covers low range (100 mTorr) and
sensor 1 covers high range (1 Torr). Switchover between sensors is done automatically according to
«Pressure control operation with 2 sensors».
0
-
10V
High range
sensor
Low range
sensor
0
-
10V
SENSOR 1
100 mTorr
1 Torr
0 mTorr
SENSOR 2
PRESSURE
0
– 1’000'000