MDM25 User’s Manual
12
97234 Issue 4, January 2018
MAINTENANCE
4 MAINTENANCE
The MDM25 is designed to operate either in static ambient conditions, or in a
fl
owing
gas stream.
The sensors are designed to have excellent performance in ambient conditions.
Therefore, a
fl
ow is not necessary to ensure that the probe is reacting rapidly to changes
in measured conditions.
If the sensor is installed in a
fl
owing sample, then it is not crucial to regulate the
fl
ow rate in order to ensure consistent performance, although it is preferable to avoid
excessive
fl
ow rates past the sensor during operation.
The use of appropriate
fi
ltering for the sample conditions is always recommended – so,
where the sample or ambient conditions may contain dust, steam or liquid water, a
suitable mesh or sintered
fi
lter should be
fi
tted. Protection caps are also available to
defend against the possibility of handling damage.
Care should be taken to avoid mechanical shock (impact) or thermal shock (sudden
temperature changes).
4.1 Probe
Calibration
Salt solutions are commonly used for the calibration of RH sensors. Michell Instruments’
calibration Control Kit is available to provide a traceable reference to verify the accuracy
of the probe.
The Control Kit can be purchased from Michell Instruments (for contact information go
to www.michell.com).
4.2 Cleaning
The enclosure can be cleaned using a mild household detergent and a damp soft cloth
or absorbent paper. Remove the connector before cleaning and dry off any moisture
before reassembly.
NOTE: Do not use any abrasives - this may cause the LCD
display to become obscured.
4.3 Probe
Replacement
The probe should be returned to Michell Instruments annually for recalibration. This
will ensure continued traceability, and will verify that it is still performing within its
speci
fi
ed accuracy.
4.4 Batteries
When the battery charge indicator icon on the display is empty, the batteries should be
replaced (see Section 2.3). Always install 3 new batteries of the same type.
