Edwards PGC201, Instruction Manual

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D0300040001EN - General equipment description
Page 5
General equipment description
PGC201
This combination instrument offers three measurement channels, two PRG and one CPG.
Thus measurement of vacuum pressures over 12 full decades from 1 x 10
-9
mbar to
atmospheric pressure is possible. Six switching thresholds permit the integration of the
PGC201 within complex vacuum control facilities. The two PRG channels are immediately
active upon powering up. The CPG channel may be switched on and off by one of the two PRG
channels or externally or manually. The operating status of the switching thresholds and the
measurement systems is displayed and signalled correspondingly through the outputs.
PRG (Pirani) method of measurement
This method of measurement covering the range of 5 x 10
-4
to 1 x 10
3
mbar utilises the heat
conductance of the gas for the purpose of measuring pressure. In order to attain a response
time which is as short as possible, all PRG instruments rely exclusively on the principle of the
controlled Pirani where the measurement filament is part of a Wheatstone Bridge. When the
temperature of the filament changes due to pressure changes, the bridge becomes
unbalanced. The quickly responding control circuitry adapts the heating power for the
filament so that the filament temperature reaches its nominal level thereby balancing the
measurement bridge again. The displayed pressure is dependent on the type of gas. By
default the display of the instrument has been calibrated for nitrogen or dry air.
CPG (cold cathode) method of measurement
This principle of measurement relies on the ion current produced when a gas discharge is
generated within the sensor. The resultant ion current from the discharge is proportional to
the pressure. This sensor arrangement allows reliable measurement in the range from
1 x 10
-9
to 1 x 10
-2
mbar. Two versions with either a NW or CF flange are available.
Connectable gauge heads
The following gauge heads can be operated by the PGC201:
Table 2 Connectable gauge heads
Gauge head Product description Item number
CPG
CPG35K - NW40 D03000100
CPG35K - DN40CF D03000110
CPG35K - NW25 D03000130
CPG35KB - DN40CF D03000140
PRG
PRG20K - NW16 Al D03000200
PRG20K - DN16CF SS D03000210
PRG20KCR - NW16 SS D03000220