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149-072011 Model 2002 Vacuum Gauge Page 13 of 38
light will now flash. Use the UP and DOWN switches to individually select the desired code. Return the
Model 2002 to the RUN mode.
Note: Factory calibration is performed using nitrogen only. Displayed pressure measurements using other gases are
based on established gas thermal conductivity data.
3.6. UNITS Mode
The Model 2002 can display the measured pressure in different pressure units, Torr, mbar or Pascal. To
switch between these units press the MODE switch until the UNITS field is lit. Press the UP and DOWN
switches simultaneously. The UNITS light will now flash. Use the UP and DOWN switches individually to
select the desired unit.
The unit’s mode is also used to display the RS-485 address, (see section 6.3).
A commonly used unit is mTorr which is also known as the micron (short for micron of Hg). One Torr is
equal to 1000 mTorr. The table below illustrates how to interpret the display in mTorr.
mTorr Conversions
1 mTorr = 1.00 x 10
-3
Torr
10 mTorr = 1.00 x 10
-2
Torr
100 mTorr = 1.00 x 10
-1
Torr
Table 2 gives conversion factors for the most often used pressure units.
Default Calibration Restoration
The UNITS mode is also used to load default calibration data in rare cases where the transducer EEPROM
has become corrupted. The default calibration data should be considered an approximate calibration
because the values entered in the controller’s software are based on averaged data collected over a large
number of transducers. While this type of calibration download is not a true calibration, it does allow the
user to return the unit to a reasonable status from which a full calibration can be easily performed.
Gas Mode Gas
Displayed Number
0.3………………...…Water Vapor
0.4………………....……..Custom
TABLE 1
0.0………………………..Nitrogen
0.1…………………...……..Argon
0.2…………………...…….Helium
To rr atm m bar P a ps i
Torr (mm Hg) 1
1.32x10
-3
1.3332 133.32
1.934x10
-2
mTorr (micron Hg)
10
-3
1.32x10
-6
0.00133 0.13332
1.934x10
-5
atm (athmosphere) 760 1 1013.23 1.013x10 14.7
mbar (millibar) 0.75
9.869x10
-4
1100
1.45x10
-2
Pa
7.5x10
-3
9.869x10
-6
0.01 1
1.45x10
-4
psi (lb/in) 51.72
6.805x10
-2
68.953 6895.3 1
TABLE 2