Vaisala DRYCAP DMT143 - Field Check Using DM70 Meter

In the following procedure, the readings of the transmitter and the reference
probe are checked simultaneously. You can also check the reference probe and
the DMT143 separately if they cannot be connected at the same time.
The messages from the transmitter will appear in English even if the MI70 has
been set to another language.
Perform the check as follows:
1. Place the reference probe and the DMT143 in the reference environment.
2. Connect the reference probe and the DMT143 to the MI70 indicator:
• Reference probe to Port I
• DMT143 to Port II
3. If you have altered the DMT143 serial port settings, switch o the other power supply
(disconnect “Analog” cable if in use) before powering up the MI70. Note that this powers
o the transmitter, and it will carry out the startup sequence when powered on again.
4. Turn on the MI70 indicator. Never connect or disconnect the MI70 indicator while it is
powered on, as this may cause incorrect values to be displayed.
5. Check and adjust the environment settings if prompted. Refer to the DM70 User’s Guide
for the settings of the DMP74B probe.
6. Disable the Auto power o function of the MI70 indicator to prevent the indicator from
powering o in the middle of the check. Check the setting in the Settings - User Interface
menu, and change if necessary.
7. The MI70 can display three parameters at one time. To compare the readings of the
DMT143 and the reference probe, select the desired parameter from the Display –
Quantities and Units menu of the MI70.
Select the same parameter from port I and II, and the delta parameter that shows the
dierence between the two. For example, ∆T
d/f
shows the dierence in dew point
between the two probes.
8. After the measurement has stabilized, check the dierence between the readings. It will
give you an indication of the approximate drift of the DMT143 and its need for calibration.
The dierence between the readings should be no greater than the combined
measurement uncertainty of the DMT143 and the reference probe.
9. Write down the results and repeat the comparison for each parameter you want to check.
DMT143 User Guide M211435EN-J
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