MKS 275420-1-GQ-T-00011, Instruction Manual

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6 Calibration
Series 275 Convectron Module with DeviceNet
Instruction Manual - 275502 43
Using the N
2
calibration to pressurize a vacuum system above about 1 Torr
with certain other gases can cause dangerously high pressures which may cause
explosion of the system. See Section 6.4 before using with other gases.
6.5 Adjustment of Convectron Gauge Zero and Atmospheric Pressure
Indications
Each Convectron Gauge has a stable, temperature compensated design and is individually
computer calibrated for N
2
. Zero adjustment of the gauge should not be necessary unless readout
accuracy is required below 1 x 10
-3
Torr or the gauge has been contaminated. Adjustment of the
atmospheric indication should not be necessary unless compensating for variations in mounting
orientation, or contamination.
For accurate readout, the vacuum and atmosphere adjustments must be made in the following order.
Atmosphere adjustment will not effect the vacuum setting, but vacuum adjustment will effect the
atmosphere setting. The subscript data is an unassigned 16 bit integer.
6.5.1 Calibrate the Vacuum Reading
1.
Evacuate Convectron Gauge to a pressure known to be less than 1 x 10
-4
Torr of N
2
.
2.
With power ON and pressure less than 1 x 10
-4
Torr for at least 15 minutes, send Parameter Object
0F, Instance 1, Attribute 1, Data 00 00, to zero the Mini-Convectron Module. See Table 5-6.
If the base pressure is between 1 x 10
-4
to 1 x 10
-1
Torr, use another gauge or pump specs to
set zero. For example: If the vacuum pump will go down to 1 x 10
-2
Torr, send 274C for data.
(Multiply the counts listed in Table 5-7 times 4 to find other values.)
6.5.2 Calibrate the Atmosphere Reading
1.
Allow the system pressure to increase to atmospheric pressure.
2.
Read the local atmospheric pressure on an accurate barometer or use the data in Table 6-2 to
set the Decimal Count value or Hex Count Value for your system.
3.
With the power ON, set the Decimal Count value or Hex Count Value for your system. For
example: at sea level, send Parameter Object 0F, Instance 2, Attribute 1, Data E0 60. See Table
5-6.
(Multiply the counts listed in Table 5-7 times 4 to find other values.)
6.5.3 Special Considerations for Convectron Gauge Use Below 10
-3
Torr
During a fast pumpdown from atmosphere, thermal effects will prevent the Convectron Gauge from
tracking pressure accurately below 10
-3
Torr. After waiting about 15 minutes, indications in the
10
-4
range will be valid and response will be rapid. Zero adjustment at vacuum may be performed at
this time (or sooner if readings in the 10
-4
range are not needed). In the 10
-4
Torr range, the indication
is resolved to about 0.1 millitorr provided the instrument has been carefully zeroed at vacuum. For
accurate use in the 10
-4
range, zeroing should be repeated frequently.