Vaisala HMT310 - Manual (Page 79)

Chapter 6 ___________________________________________________ Calibration and Adjustment
VAISALA ________________________________________________________________________ 79
Example Multipoint Adjustment Procedure
1. Connect the HMT310 to a computer (see section Serial Line and
Analog Communication Options on page 36). Open a terminal
program.
2. Issue the PURGE command to carry out the chemical purge, and
wait for six minutes for it to complete. Transmitters without the
chemical purge feature (selected when ordering) do not respond to
the command.
>purge
Purge started, press any key to abort...
3. Press the adjustment button once (see Figure 18 on page 74).
4. View the currently applied standard user adjustment offset and gain
using the L command. If offset is zero and gain is one (example
shown below), no user correction is applied:
>l
RH offset : 0.00000000
RH gain : 1.00000000
T offset : 0.00000000
T gain : 1.00000000
5. If an RH offset or gain is in place, write down the adjustment and
then clear it by writing zero to RH offset and one to RH gain using
the LI command (see section Revert to Factory Calibration on page
70) :
>li
RH offset : 0.00130000 ? 0
RH gain : 1.04000000 ? 1
T offset : 0.00000000 ?
T gain : 1.00000000 ?
6. You must now prepare a list of 3 ... 8 correction points using a
humidity generator or salt solutions (for example, using the
HMK15 Humidity Calibrator). You must measure the transmitter’s
RH reading at each point, and make a note of the reference RH
reading. Here is an example list for a four-point correction:
Table 18
Example List for Multipoint Correction
Point Number Transmitter’s Reading Reference
1 12.2% RH 11% RH
2 34% RH 33% RH
3 75.5% RH 75% RH
4 97.3% RH 97% RH