easy2log© RT0005 Technical Information Manual
12
Histogram functionality description
The easy2log
©
RT0005 tag allows to define up to 16 different histograms bins. The user is able to decide the upper and
lower temperature limits for each bin: the lower limit of each bin is equal to the upper limit of the previous bin while
the upper limit can defined by the user (BIN_HLIMIT_[X] where is X is the index of the histogram bin). The first bin
starts always from the lower temperature limit of the tag while the upper limit of the last bin is always the higher
temperature limit of the tag.
Each histogram bin has a bit that allows to enable/disable the counter for the bin (BIN_ENABLE register). If the bin is
enabled, the corresponding counter (BIN_COUNTER[X]) is incremented when the sampled temperature value is greater
to the lower limit and less or equal than the higher limit. If the bin is not enabled the temperature values in the interval
defined by the corresponding bin are not counted.
For each bin it is possible to define a threshold value (BIN_THRESHOLD_[X]) in order to generate an alarm when the
counter is greater or equal to the threshold value. The generation of the alarm can be disabled setting the threshold to
0xFFFF (default value).
It is also possible to define a different sampling interval for each different bin in order to permit a fine grained sampling
in critical temperature ranges and a more relaxed sampling in standard temperature conditions. The sampling interval
time is modified after the detection of the first temperature sample value in a new bin (if the value of the temperature
falls in the same bin the sampling time dos not change, if it falls in a new bin the sampling time is updated with the
value of the BIN_SAMPLETIME[X] register where X is the index of the new bin).
Histogram bins configuration can be used also to control the storage of the samples inside the logging memory: for
each bin (if enabled) the user can choose to store or not in the memory the temperature value (depending on the state
of the corresponding bit in the BIN_ENA_SAMPLE_STORE register) and the time stamp (depending on the state of the
corresponding bit in the BIN_ENA_TIME_STORE). Disabling the sample storage for accepted temperature ranges can
provide a better handling of long term deliveries due to the memory saving. In this case it is necessary to enable the
storage of absolute timestamps together with the samples out of the acceptance range in order to keep track of the
chronological sequence. At the same time, the bin counter can be enabled also for the accepted temperature range in
order to have a feedback on the temperature trend for the entire delivery. Due to the availability of a large number of
bins, the accepted range can be divided in more than one bin in order to have finer grained information on the
temperature trend.
Examples of usage:
Let suppose that the user wants to monitor the temperature trend for frozen food, we can define some histogram bins
as follows
:
Bin
Low Limit
(°C)
High Limit
(°C)
Enabled
Threshold
Store
Samples
Sampling Interval (min.)
0
-20
-15
Yes
0
Yes
15
1
-15
-10
Yes
3
Yes
10
2
-10
0
Yes
2
Yes
5
3
0
70
Yes
1
Yes
1
Tab. 2.2: Example of histogram bins for frozen food
With this configuration the tag generates an alarm if the temperature was between -15°C and -10°C for a minimum
amount of time ranging from 20 min. to 34 min. and 59 sec. or if it was between -10 °C and 0 °C for a minimum amount
of time ranging from 5 min. to 14 min. and 59 sec. or greater than 0 °C just for a minimum amount of ranging from 1
sec. to 4 min. and 59 sec. (see Fig. 2.1 and Fig. 2.2)
