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Displayed Pressure
Analog Output - volts
LO
0.000
0 mTorr (µbar) or less
0.000
10 mTorr (µbar)
0.500
20 mTorr (µbar)
0.651
100 mTorr (µbar
1.000
10 torr (mbar)
2.000
990 torr (mbar)
2.998
OFF
or
HI
3.000
Analog Output - volts
pressure- mtorr (µbar)
0.100
1.58
0.500
10.0
0.600
15.8
1.100
158
2.000
10,000
Figure 6: Analog Output Voltage vs. Pressure
M. Serial Interface
The serial port gives pressure readings when requested by the RS-232 terminal. The interface is
standard RS-232 format; 9600 baud, 8-bits, no parity, 1 stop bit. The interface is through the
DB15 accessory connector.
pin 7 is Tx (signal from terminal to the 906A)
pin 8 is Rx (response from the 906A to the terminal)
pin 9 is return (ground).
To get pressure readings,
send a lower case “p” (ASCII value 112). Output is converted from
the digital display, in the following format:
WXY
e
Z
, where
WXY
is the multiplier and
Z
is the exponent; Some examples follow:
displayed pressure
Serial Output
OFF
-99e-3
LO
-20e-3
0.0 mTorr
0.0e-3
0.8 mTorr
0.8e-3
2.8 mTorr
2.8e-3
-1.6 mTorr
-1.6e-3
57.1 mTorr
57.1e-3
2.34 torr
2.34e+0
135 torr
135e+0
HI
999e+0
Figure 7: Serial RS-232 Output Vs. Pressure: Examples
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