Vaisala PTB330 - Manual (Page 115)

Chapter 6 ___________________________________________________Calibration and Adjustment
VAISALA ______________________________________________________________________ 113
Pressure Adjustment
In PTB330, the raw measured pressure value of each barometer
module is first corrected using the corresponding multipoint
adjustment values. The additional linear adjustment (if enabled) is
applied to the corrected values. This allows you to fine-tune the
pressure display using the linear adjustment without performing a
complete readjustment for the barometer module, see Figure 45
below.
Figure 45 PTB330 Adjustments
For correct adjustment, the existing adjustment must be disabled
before measuring the new adjustment data. If you are going to do only
offset or linear adjustment (one to two pressure points), leave the
multipoint adjustments active. If you want to perform a complete
readjustment of your PTB330, disable both the multipoint and the
linear adjustments, and calibrate the instrument at 2…8 pressure
points. In such a case, the new adjustment values are entered to the
multipoint adjustment function and the linear adjustment is not used
(that is, it is left disabled).
NOTE You can set up a 1-point offset adjustment in prevailing ambient
pressure using a suitable reference instrument, such as Vaisala
Barometric Pressure Transfer Standard PTB330TS.