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Model 2002 page 15
Note: Factory calibration is performed using nitrogen only. Displayed pressure mea-
surements 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 units 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
To r r
10 mTorr = 1.00 x 10
-2
To r r
100 mTorr = 1.00 x 10
-1
Torr
Table 2 gives conversion factors for the most often used pressure units.
Torr (mm Hg)
mTorr (micron Hg)
atm (athmosphere)
mbar (millibar)
Pa
psi (lb/in ) 51.72
7.5x10
0.75
760
10
1 1.32x10
1.32x10
1
9.869x10
9.869x10
6.805x10 68.953
0.01
1
1013.23
0.00133
1.3332 133.32
.13332
1.013x10
100
1
6895.3
1.934x10
1.934x10
14.7
1.45x10
1.45x10
1
psiPambar
TABLE 2
Torr
-2
-3
-5
-2
-6
-4 -2
-4
-3
-3
-6
atm
Default CalibraDefault Calibra
Default CalibraDefault Calibra
Default Calibra
tion Restoration Restora
tion Restoration Restora
tion Restora
tiontion
tiontion
tion
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 approxi-
mate 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.