Brooks Instrument CMC Series - Manual (Page 11)

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3.0 OPERATION
For most accurate pressure measurement, allow the CMC Series to warm up for
at least 15 minutes. After installation, periodically check the zero output reading
to verify correct output. Adjust the zero potentiometer, if incorrect (See Calibra-
tion and Adjustment Section for Zero adjustment instructions).
Table 1 indicates the lowest pressures available for reading and pressure control
for each range of the CMC Series. The lowest suggested pressure available for
reading is limited by the resolution and the accuracy of the CMC Series. This is
directly related to the electrical noise on the signal output and can be signifi-
cantly effected by incorrect electrical ground connection, or connection to an
electronically noisy power supply or readout instrument. Improved results may
be obtained if the transducer is operated in an environment with stable tempera-
ture and air flow. The lowest recommended pressure used for control applica-
tions, such as a closed loop downstream pressure control system is based on a
signal output of 50 mV.
Table 1: Recommended Lowest Pressures Available for Reading &
Pressure Control
Full scale Range
Recommended Lowest
Pressure Reading
Recommended Lowest
Pressure for Control
10 Torr 0.005 Torr 0.05 Torr
20 Torr 0.010 Torr 0.10 Torr
100 Torr 0.050 Torr 0.50 Torr
1000 Torr 0.500 Torr 5.00 Torr
10 mbar 0.005 mbar 0.05 mbar
100 mbar 0.05 mbar 0.5 mbar
1000 mbar 0.5 mbar 5 mbar
1.333 kPa 0.0006 kPa 0.0066 kPa
13.333 kPa 0.0066 kPa 0.0666 kPa
133.32 kPa 0.0666 kPa 0.6666 kPa
Table 2: Applications
Application Matrix
Full Scale Pressure Range
(Torr)
10 20 100 200 1000
Pressure Measurement R R R R R
Upstream Pressure Control R R R R R
Back Side Wafer Cooling A A R R R
Downstream pressure Control R R R R R
R = Recommended
A = Acceptable
3.0
_OPERATION