HELIX GRANVILLE-PHILLIPS Convectron ATM, Instruction Manual

Page: 65 / 98

RS–485 Module Operation
Convectron
®
ATM Vacuum Gauge Module Instruction Manual
57
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4.9 Modules operating below
10
–3
Torr
During a fast pumpdown from atmospheric pressure, thermal effects
temporarily prevent the module from measuring pressure accurately below
10
–3 Torr. After approximately 15 minutes, pressure indications the 10 –4
Torr range will be accurate and response will be rapid.
When pressure indication in the 10
–4
Torr range has stabilized, a
Convectron gauge calibration at vacuum chamber pressure may be
performed. The calibration may be performed at a higher pressure if
readings in the 10
–4 Torr range are not required. In the 10 –4 Torr range,
resolution is ±0.1 millitorr, if the Convectron gauge has been properly
calibrated at vacuum chamber pressure. If the module frequently operates
in the 10
–4
Torr range, Convectron gauge calibration at vacuum chamber
pressure should be performed frequently.
4.10 Calibrating the
differential pressure
sensor zero
Setting the differential pressure sensor zero decreases measurement error of
the sensor. Differential pressure sensor zero is the pressure offset error for
the sensor when atmospheric and vacuum chamber pressures are equal (the
pressure differential is zero).
1. Allow atmospheric and vacuum chamber pressures to achieve the
same value. This is a pressure differential of zero.
2. Send a calibration at zero (TO) command, in the pressure unit that has
been programmed for the module (see page 55):
TO command from host: #01TO
↵
Example response from module: *01 PROGM OK
↵
The last character in the TO command is the capital letter “O”, not a zero.
If the module returns a message other than “*01 PROGM OK
↵
” in response
to the TO command, the differential pressure sensor zero calibration has
failed. See page 64 to troubleshoot the problem.
4.11 Reading the firmware
version
The example read firmware version (VER) command causes the module to
return a value that represents the Helix Technology internal part number
16400 and firmware revision 01 for the module:
Example VER command from host: #01VER
↵
Example response from module: *01 16400–00
↵
• The first five digits are the internal part number.
• The two digits following the – sign are the firmware revision.