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Temperature calibration (ct) – Vaisala HMM100 User Manual

Page 58

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User's Guide _______________________________________________________________________

56 ___________________________________________________________________ M211024EN-C

Temperature Calibration (CT)

The procedure below describes a temperature (T) measurement

calibration using serial line commands. You can use the procedure to do

a one-point calibration (offset) or a two-point calibration (offset and

gain). For two-point calibration, the second reference point must be at

least 20 ºC warmer than the first.

Temperature measurement is not controlled by the trimmers, so do not

adjust them during temperature calibration.

1.

Connect the USB cable to the service port on the module, and to a

USB port on your PC.

2.

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.

3.

Verify that the connection works by giving the ? command:

>?

If the module does not respond with device information:

- Check that the module is powered
- Try the ?? command in case the module is in POLL state, open the

line using OPEN command if necessary

- Check your serial line settings and cable connections
- Power off the module, unplug the USB cable, restart the terminal

application, and try again.

4.

When your serial connection is working, use the L command to see

the current user adjustment parameters and the status of the

trimmers. Write down the T offset and gain values so you can

restore them manually using the LI command, if necessary.

>l

5.

Use the ERRS command to see that no errors are active:

>errs

6.

Use the PASS command to enable the advanced commands:

>pass 1300

7.

Insert the probe in the temperature reference and wait for 20 – 40

minutes for the reading to stabilize.