Michell Instruments MDM300 I.S, User Manual

Page: 43 / 72

MDM300 I.S. User’s Manual
Michell Instruments 35
OPERATION
3.6.2 Measurement Guide
1. Follow procedure A and note the result.
2. Turn the instrument off.
3. If you wish to measure at sample pressure then use the Michell Humidity
Calculator (http://www.michell.com/uk/downloads/humidity_calculator.
msi) to convert this result back to the equivalent at your sample pressure.
4. Using this converted result, and the table below, find the appropriate
procedure to measure your sample.
Dew Point
Measure at
Sample Pressure
> 2.5 barg
Measure at
Atmospheric Pressure
>-40°C Procedure B Procedure A
<-40°C Procedure C Procedure A
Table 11 MDM300 I.S. Measurement Procedures
A Standard Purge (Atmospheric Measurement)
1. Connect the MDM300 I.S. to the sample gas stream.
2. Adjust the flow rate, using the inlet flow control valve, to between 0.2
& 0.5 Nl/min (0.5 & 1 scfh). The outlet flow control valve should be fully
open.
3. Turn the instrument on - the initialization period begins automatically.
The page will show a countdown of the remaining initialization time. The
status display will read
‘Initializing internal sensor
’
.
4. After Initialization, the instrument will begin Measurement mode. During
the first few minutes of Measurement mode, the displayed moisture value
will drop rapidly below the actual moisture value, before returning to a
stable reading. The instrument display will show an initial measured
value, and the status display will show ‘
Measurement in progress’
.
5. Once ‘
Measurement in progress’
has disappeared, the instrument is
close to the final dew point. Depending on the conditions, it may continue
to respond for a number of minutes before tracking the measured dew
point.