Vaisala HMT330 - Manual (Page 163)

Chapter 7 ___________________________________________________ Calibration and Adjustment
VAISALA _______________________________________________________________________ 161
Multipoint Adjustment Using Serial Line
You can use the MPC command (introduced in software version 5.14) to
perform a multipoint adjustment to the relative humidity measurement.
Due to the linear response of the HUMICAP
®
sensor, the standard two
point adjustments are recommended for all users. Use multipoint
correction only if:
- You have a requirement to adjust the relative humidity measurement
in 3 ... 6 adjustment points.
- You are interested in a narrow range of measurement and want to
optimize the RH measurement performance for that range.
Multipoint adjustment works by means of a correction table that holds
2 ... 6 adjustment points. The idea is that for every point, you enter the
RH reading that the transmitter shows, and the correct humidity reference
value. You can select any references points in range 0 ... 100 %RH, but
Vaisala recommends that the difference between the lowest and highest
reference point is at least 50 %RH.
NOTE Multipoint adjustment is applied “on top” of the standard user-made two
point adjustment (done with CRH command, push-buttons, or display). It
is recommended that before you start using the MPC command, you clear
the existing humidity adjustment. This is done as part of the example
multipoint adjustment procedure provided here.
MPC Command Syntax
MPC [quantity] [function]<cr>
where
quantity = Quantity to be adjusted. The only available quantity is
RH.
function = Desired function. The options are:
ON – Enable multipoint correction.
OFF – Disable multipoint correction.
LIST – Show correction table.
INIT – Start entering values in correction table.
CLEAR – Remove all values from correction table and
disable multipoint correction.