Vaisala DMT152 - Manual (Page 59)

Chapter 6 _______________________________________________________________ Maintenance
VAISALA ________________________________________________________________________ 57
Field Check Using DM70
To check of the accuracy of the DMT152 in the field, you need the
following equipment:
- A fully charged MI70 indicator (the measurement display that is
included in the DM70 package)
- A calibrated reference probe that is suitable for the intended
measurement environment and dewpoint range. You can use a DMP74
probe from the DM70 for dewpoint down to -60 °C
(-76 °F), or a second DMT152 for full measurement range.
- A connection cable between DMT152 and the MI70 indicator (Vaisala
order code 219980).
- A reference environment with a stable dewpoint and temperature in a
suitable range for both probes. The normal measurement environment
of the transmitter can also be used, if it meets these criteria.
NOTE In the procedure below, the readings of the probes are checked
individually. You can also perform the field check so that you connect
the reference probe simultaneously with the DMT152 you are checking.
In this case, you need two of the connection cables if you are using a
DMT152 also as the reference probe. Also, you must power one of the
transmitters by other means than the MI70.
Perform the check as follows:
1. Place the DMT152 in the reference environment (unless it is
already). You can perform the check even if the DMT152 is
currently being powered and used, as long as there is no cable
connected to connector II.
2. Connect the MI70 connection cable between the MI70 indicator
and connector II of the DMT152.
3. Turn on the MI70 indicator. If the analog channels of your
DMT152 are configured to use the current output, and if the
DMT152 is powered by the MI70, you will see an error message
that indicates the supply voltage is too low for running the actual
analog output. This is expected behavior; press OK to acknowledge
the error and continue the field check.
0805-014
Figure 22 Supply Voltage Too Low for mA Output Error