Chapter 6 ______________________________________________________________ Maintenance
VAISALA _______________________________________________________________________ 57
Calibration and Adjustment
DPT146 is fully calibrated as shipped from factory. The recommended
calibration interval is two years. If there is a reason to believe that device
is not within the accuracy specifications, you can perform a field check
using the DM70 hand-held dewpoint meter, or an MI70 indicator with
another DPT146.
If the field check indicates that the DPT146 is not within its accuracy
specifications, contact a Vaisala Service Center or your local Vaisala
representative to have the DPT146 adjusted.
Field Check Using an MI70 Indicator
Vaisala recommends the following equipment for field checking:
- 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. The DMP74B probe
is recommended for checking the dewpoint and temperature
measurement accuracy. For checking all parameters, you can use
another DPT146 transmitter as a reference.
- You also need a connection cable (Vaisala order code: 219980) to
connect the DPT146 to the MI70 indicator. If you have two DPT146
transmitters, you need two cables.
NOTE
In the procedure below, the readings of the transmitter and the reference
probe are checked simultaneously. You can also check the reference
probe and the DPT146 separately if they cannot be connected at the
same time.
Perform the check as follows:
1.
Place the reference probe and the DPT146 in the reference
environment.
2.
Connect the reference probe and the DPT146 to the MI70 indicator:
- Reference probe to Port I
- DPT146 to Port II
3.
Turn on the MI70 indicator.
4.
Check and adjust the environment settings if prompted. Refer to the
DM70 User’s Guide for the settings of the DMP74B probe.
