Thermo Scientific MIRAN 205B Series Instruction Manual page 92

Portable ambient air analyzer
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Chapter 7 Configuration and Setup
If Batch Mode is enabled, the analyzer performs a trap and purge routine. This turns the
pump off during the measurement of all analytical wavelengths. This ensures the sample
is measured at all analytical wavelengths, allowing for proper compensations if
necessary. Once the analysis is completed, the pump is turned back on to draw in a new
sample, and the process is repeated.
Batch Purge %
Batch Percent of Purge specifies the percent of maximum gas cell purge to perform
during a batch sampling mode. As described in "Batch Sample", above, Batch Percent of
Purge can be changed when faster updates of the data are required. The batch cycle
consists of three portions. In the first portion, batch purge, the pump draws in a new
sample or batch of gas. This lasts 20 seconds if Batch Percent of Purge is set to 33%. In
those 20 seconds about 4.5 liters (2 volumes) of gas are drawn into the cell. By entering
25%, this portion of the cycle lasts 15 seconds and draws about 3.5 liters (1.5 volumes) of
gas.
The second portion of the cycle is the measurement of the gas at each of the wavelengths.
To see the analyzer measuring the wavelengths, press the up arrow key to view the
Intensity or Absorbance screen (if enabled). The third portion of the cycle is the display
of the data.
By changing the Batch Percent of Purge to a lower value, reduce the cycle time.
However, by doing this, each successive sample measurement shows a smaller step
change since the gas cell is not being refreshed as quickly. In a static or constant
concentration location, this may not be a problem.
In the Batch Percent of Purge parameter, the last batch percent of purge configured is
shown on the display. If this is the desired percent of purge, press
. The display
ENTER
changes to the next parameter to be configured. To change the batch percent of purge,
press
. The Batch Percent of Purge Enter Display appears. Key in the desired percent of
1
purge (0 to 100) and press
. If the entry is valid, the display responds "-
ENTER
ACCEPTED-" and then changes to the next parameter to be configured.
Measurement Absorbance  Concentration
Measurement Absorbance  Concentration specifies the coefficient for a P, Q, and R
parameter or the maximum absorbance value, any of which may be assigned to Range 1,
2, or 3 for the application. The last measurement Absorbance  Concentration value for
each range configured is shown on the display. To accept this data, press
. The
ENTER
display returns to the Primary Name Display (see above). Press
to change the
1
absorbance values,. The Meas Absorb  Conc Range Select Display appears (see Meas
Absorb  Conc Range Display, below).
7-38

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