PST MICHELL Instruments MDM300, User Manual, Page: 28 / 70

MDM300 User Manual
20 97122 Issue 16.2 June 2022
OPERATION
3.2 Instrument Start-Up
Dewpoint External
°C
70.1
6.9
°C Temp.
Dewpoint External
°C
70.3
6.8
°C Temp.
Measurement in progress
Internal
Initializing: 01:32
70.4
°C Temp.
Initializing internal sensor
MDM300
System Initializing
Figure 15 Start-Up Sequence
At switch on, the instrument goes through an
initialization process lasting several minutes. During
this time the internal sensor is heated to a maximum
of +70 °C (+158 °F). The heating process increases
the mobility of water molecules and accelerates
equilibrium with the passing sample gas .
During this period the sample gas flow purges the
system. After this period, the sensor will be dried to
below the dew point of the gas to be measured. The
heating is then switched off and the display becomes
dynamic. Figure 14 shows a typical start-up sequence.
At switch-on, the System Initializing Page is displayed
for several minutes during which the page will show a
countdown of the remaining initialization time.
NOTE:
The initialization stage is skipped if the initial
dew point is detected to be within 2 ° C of the
dew point when the instrument was switched
off.
During this period, gas will be flowing through the
sensor and can be externally regulated to meet the
instrument’s flow requirements, and the real time
sensor temperature is indicated in the secondary
display area. The initializing icon (item 6 in
Figure 3)
is displayed in the status area and the keyboard is
locked out until the initialization period has expired.
It is possible to terminate the initialization process before the initialization period
has timed out by pressing the

and

keys simultaneously. This action aborts the
instrument’s response enhancement system and allows the operator to make an
immediate measurement if the measured dew point is wetter than -20 °Cdp (-4 °Fdp).
While the initialization process is in progress, the backlight time-out is inhibited and, if
any external sensor has been configured and connected to the instrument, display of
the external sensor reading is also inhibited.
After the end of the initialization period, the display reverts to Measurement Mode
displaying dew point (in the currently selected unit) in the primary display area, and any
external sensor reading in the secondary display area. By default, the internal temperature is
displayed in the secondary display area if no external sensor is configured.
If an external sensor has been selected but has either not been connected or is giving
an over-range indication, a flashing External Sensor Error message (alternating with a
Measurement in progress
message) will be displayed.
While the Quick Response Algorithm is in operation a Measurement in progress
message is displayed. After this, depending on the sample conditions, the instrument
may continue to respond to the final dew-point for a number of minutes. This is further
explained in Section 3.6.