Vaisala PTU300 - Manual (Page 175)

Chapter 7 ____________________________________________________ Calibration and adjustment
VAISALA _______________________________________________________________________ 173
To start, remove the filter from the probe and insert the probe into a
measurement hole of the driest reference chamber you intend to
use. Proceed from low to high humidity. Remember to allow at
least 30 minutes for the sensor to stabilize at each point.
7. When done preparing the list, remove the probe from the last
measurement chamber and re-attach the filter.
8. On the serial line, issue the MPC RH INIT command and start
entering the readings and reference points from the list you
prepared in step 6. When you have no more points to enter, press
enter to save the points.
>mpc rh init
1 Reading : ? 12.2
1 Reference: ? 11
2 Reading : ? 34
2 Reference: ? 33
3 Reading : ? 75.5
3 Reference: ? 75
4 Reading : ? 97.3
4 Reference: ? 97
5 Reading : ?
Mpc points saved.
9. Issue the MPC RH LIST command to verify the list you entered:
>mpc rh list
MPC : OFF
# Reading Reference Correction
1 12.20 11.00 -1.20
2 34.00 33.00 -1.00
3 75.50 75.00 -0.50
4 97.30 97.00 -0.30
10. If you are satisfied with the correction list, enable multipoint
correction by issuing the command MPC RH ON.
>mpc rh on
11. Multipoint adjustment of relative humidity is now complete.