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Page 33
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Operation
D397-01-880 Issue E
4.8.11
Capacitance Manometer Gauges (D39702000 only)
Capacitance Manometer Gauges are often abbreviated to ‘Capmans’ and are also referred to as using the brand model
name of Barocels®.
Supported types are 600 series, 622, series, 655 series and 658 series only. For a detailed specification and
instructions regarding the use of Capmans refer to the instruction manual for the specific model.
Capacitance Manometer gauges are gas independent and are available in a very wide choice of ranges. They are
unique in the Edwards range of vacuum gauges in requiring a
±
15 V power supply rather than a +24 V power supply.
This power supply is provided by D39702000 TIC units.
The output for all types is 0-10 V d.c. for the particular gauge range with a higher voltage indicating an over range
and a negative voltage indicating that gauge head or TIC requires zeroing. Almost always the ranges are absolute so
a 0-10 mbar Capman will output 10 V at 10 mbar pressure.
Capman gauge have menu options in addition to those shown at the beginning of
Ion Em Timeout
The IGC has either failed to establish emission or lost emission. There are a large
number of possible reasons for this including broken gauge head electrode or filament
and disconnected cables. Other less obvious reasons include filament contamination,
inappropriate head or filament selection, power supply overload or pressure too high.
IGC internal pressure limit is based upon output signal voltage at 9.84 V (
±
0.11 V). If
the gauge head sensitivity is 10/mbar this means pressure will need to be below 5.4 x
10
-3
mbar to guarantee emission, but as a pressure the value will vary with head
sensitivity.
Table 27 - Setup options Capacitance Manometer
Menu option
Description
Range
It is essential the correct range is selected otherwise the pressure readings will be
completely erroneous.
Range options are: 2000, 1000, 200, 100, 20, 10, 2, 1, 0.2, 0.1, 0.05.
‘Scroll’ to ‘Range’ and press ‘Select’. ‘Scroll’ to change option and press ‘Select’ for
change to occur.
Note:
0.05 mbar Capacitance Manometer gauges set to kPa will be displayed in
Pascals.
Units
This is the range units NOT the display units e.g. a Capman can be a 10 Torr range but
still have the pressure displayed in mbar. The correct option (mbar or Torr) must be
selected to prevent erroneous pressure readings.
‘Scroll’ to ‘Units’ and press ‘Select’. ‘Scroll’ to change option and press ‘Select’ for
change to occur.
Set Zero
The output of a capacitance manometer gauge should be 0 V at the bottom of its
operating range which for almost all gauges is absolute vacuum. It is quite normal to
observe a small amount of drift in this zero pressure reading, either positive or
negative.
The zero can be reset by either using the pot on the gauge (preferable) or by
introducing a corresponding offset in the TIC reading. The latter method can only be
accomplished if the gauge output voltage is less than 100 mV.
‘Scroll’ to ‘Set Zero’ and press ‘Select’.
‘Command Sent’ appears for 1 second to confirm zero demanded. If the gauge voltage
is too high for the zero to take effect, a warning message will be generated.
Table 26 - Diagnostic messages (continued)
Diagnostic Messages
Description
