Chapter 5 _______________________________________________________________ Maintenance
VAISALA ________________________________________________________________________ 59
- PC with a terminal application.
- One humidity reference. One-point adjustment with a single
< 50 %RH reference will adjust the
offset
parameter of the
measurement. One-point adjustment with a single > 50 %RH
reference will adjust the
gain
parameter of the measurement.
The procedure below uses the HMK15 Humidity Calibrator. LiCl salt
(11 %RH) is used as the reference point.
1.
Connect the USB cable to the PC, but do not connect it to the probe
yet.
2.
Remove the filter from the probe and insert the probe in the LiCl
salt chamber of the humidity calibrator (11 %RH).
3.
Start a terminal application and set the correct connection settings.
The default serial settings are
19200 8 N 1
. Remember to check
which COM port the USB cable is using.
4.
Wait for 20 – 40 minutes for the humidity to stabilize.
5.
Start the terminal session and connect the USB cable to the probe.
If your probe is in the analog output mode, you need to press Enter
a few times to start it in RS-485 mode.
6.
Verify that the connection works by giving the
?
command:
?
If the probe does not respond with device information:
- Disconnect the USB cable from the probe and retry. If your probe
is in the analog output mode, press Enter a few times immediately
after connecting the USB cable.
- Try the
??
command in case the probe is in POLL mode, open the
line using
OPEN
command if necessary.
- Check your serial line settings and cable connections.
7.
When your serial connection is working, use the L command to see
the current user adjustment parameters.
l
8.
Use the
ERRS
command to see that no errors are active:
errs
9.
Give the
CRH
command, with the %RH value of the reference as a
parameter (in this case 11 for LiCl):
crh 11
OK
10. Check with the
L
command that the user adjustment parameters
have changed.
