Teledyne 9110E - Nitrogen Oxides Analyzer - Manual (Page 114)

Operating Instructions Model 9110E Instruction Manual
100 M9110E Rev B
6.10.2.6. Sample Period and Report Period
The iDAS defines two principal time periods, the SAMPLE PERIOD, which is the time
interval at which data are sampled (in volatile memory; not stored permanently), and the
REPORT PERIOD, which is the time interval of which data are permanently stored to the
Disk-on-Chip data storage and reported to the communication ports.
The REPORT PERIOD is typically used as the time interval between two permanently
stored data points. The SAMPLE PERIOD is set to one minute by default and determines
the frequency of data collection, i.e. how many times the iDAS records a parameter and
stores it in a (volatile) data array for further processing and averaging. In conjunction with
the REPORT PERIOD, the SAMPLE PERIOD determines the number of data points in each
average value.
If, for example, the NO
X
concentration parameter is configured with a SAMPLE PERIOD set
to once per minute (default setting) and the REPORT PERIOD set to once per hour, the
resulting data will be hourly, arithmetic means calculated from N=60 data points. Calibra-
tion and hold-off procedures as well as power-outs during that one hour will reduce the
number of records per concentration average. For statistical analysis, the number of records
per average data point for any given parameter within one data channel can also be stored.
Configuring the SAMPLE PERIOD and the REPORT PERIOD for the same value, for
example once per hour, will result in an instantaneous reading once per hour. This value
would be the same as a reading configured for an instantaneous (INST) data type once per
hour instead of an AVG type.
SAMPLE PERIOD and REPORT PERIOD are defined to be from the beginning to the end
of the respective clock interval. A one-minute period starts and ends with the full minutes of
the analyzer clock, an hourly period starts and ends with the full hour of the analyzer’s
clock and so on, even if the iDAS data collection was started within those periods. A one-
minute data point, which is the lowest setting for any period, is always an instantaneous
value, even when configured as an AVG event (although that data point is internally
averaged over about 30 milli-seconds of analog data readings).
Note on averages in progress when instrument is powered off:
The iDAS is capable of averaging parameters over very long time intervals (REPORT
PERIOD up to 366 days). If the instrument is powered off during an averaging interval and
before the average is permanently stored in memory, the samples accumulated so far for
that REPORT PERIOD are lost. On the other hand, if the instrument is powered up during
an averaging interval, the iDAS begins averaging samples from that point onward (or after
the hold-off period) until the scheduled end of the REPORT PERIOD when the data point is
permanently stored.