INFICON 2020ComboPRO Portable Photoionization Detector - Manual (Page 60)

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down to 0. So, the displayed number shows the remaining measuring time.
SAMPLE DONE signaled in the display indicates that the measurement is finished.
The benzene pre-filter tube (Part Number F1760160) is a one-use device and cannot
be used for a second measurement. Repeatedly pressing the SAMPLE key will call
up the information that the benzene pre-filter tube in use is no good and that a new
benzene pre-filter tube must be put into the pre-filter tube holder. Only after
inserting a new tube will pressing the SAMPLE key start a new measurement.
Benzene Sample Analysis Mode
The user is prompted through the basic procedures for taking benzene samples.
At the end of the sample period, the user is advised that the tube life is used up and a
new tube should be inserted.
Datalogger
Interval Operation
The microprocessor accumulates all readings in an averaging interval that you
select, and determines the minimum, average and maximum readings. It stores these
numbers along with the highest priority instrument status and the most recent time
and date.
The recorded data can now be reviewed and edited. Recorded data can also be
printed using the PC. For each averaging interval, the 2020ComboPRO prints the
minimum of all the minima, the average of all the readings for the interval and the
maximum of all the maxima.
In PEAK mode, the reading is updated once a second. In the background, the
2020ComboPRO datalogger is sampling the concentration and measuring min, max,
and average concentrations for the selected averaging interval. At the end of every
interval, one entry is placed in the datalogger until the datalogger is full.
In STEL mode, 15 samples are combined to form a 15-minute average. Once every
minute, the oldest of the 15 samples is replaced with a new one-minute average.
This moving average provides a 15-minute average with a one-minute update rate so
the meter display will only update once every minute. STEL is set to zero each time
the instrument is turned on.
TWA mode sums concentrations every second until 8 hours of data have been
accumulated. Once 8 hours of data have been summed, the accumulation stops.