HVG-2020B Instruction Manual
EAR99 Technology Subject to Restrictions Contained on the Cover Page
Page 25 of 40
temperature. The span error cannot be eliminated, but is typically less than 0.2 % of reading above 10 Torr and
typically less than 2% of reading below 10 Torr over -20 to 70 °C.
Pirani and Gas Interactions
While the Piezo operates independently of any gas, the Pirani is affected by different gases. To allow for
accurate measurement of vacuum in a specific gas, there are six pre-defined gases with the option for two
custom gases. The values for the pre-defined gases are not variable, but the custom gas options can be
changed using the R9 and R10 commands when a custom gas is selected. The custom gas values can also be
used to perform a calibration in the actual gas as described in Section 4.7.
Gas Name Gas Factor Gas Bend Factor
Nitrogen
1
1
Air
0.999
1.052
Helium
1.089
-0.676
Argon
1.512
0.881
Hydrogen
0.656
-0.545
CF4
1.015
2.853
SF6
0.913
0.4327
Custom 1
1
1
Custom 2
1
1
Calibration Procedure
NOTICE:
The HVG-2020B is calibrated in nitrogen at the factory and any attempt to adjust the values
associated with it will void the calibration.
Nitrogen Calibration
The HVG-2020B calibration requires digital communication. See Section 5.
1.
Attach the HVG-2020B to a vacuum system and pump down below 0.0001 Torr
2.
Make certain the instrument has been warmed up for 2 hours before proceeding.
3.
Unlock the instrument by typing
FLOK=1234
4.
Set the temperature to ambient temperature near the gauge if necessary:
TEMPSET=##.#
5.
Zero the instrument by sending the
ZRO
command.
6.
Backfill with nitrogen to between 0.1 and 1 Torr. Set the Pirani mid value equal to the value indicated
by the pressure reference:
RMID = 0.###
7.
Backfill with nitrogen to between 20 and 50 Torr. Set the Pirani high value equal to the value indicated
by the pressure reference:
RHIGH = ##.##
8.
Backfill with nitrogen to atmospheric pressure. Set the instrument span to equal the value indicated by
the pressure reference:
SPAN=###.#