Vaisala HMP110 - Manual (Page 58)

User's Guide ______________________________________________________________________
56 __________________________________________________________________ M211060EN-E
Two-Point Adjustment of RH
Measurement (HMP110 and HMP113)
To perform a two-point adjustment to the capacitance measurement of
the HMP110 or HMP113 you need:
- The Vaisala USB cable (Vaisala order code: 219690)
- PC with a terminal application.
- Two humidity references. The first point requires a < 50 %RH
humidity reference, the second point must be > 50 %RH. There must
also be at least 30 percentage point difference between the references.
The procedure below uses the HMK15 Humidity Calibrator. LiCl salt
(11 %RH) is used as the first reference point, NaCl (75 %RH) as the
second.
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