Event Logger Operation (Model L404) - AEMC Simple Logger II User Manual

4.9 Event Logger Operation
(Model L404)
The Model L404 monitors up to four channels for the occurrence of events
and stores information about each event. The rate at which each input is
tested for the event status is defined by the sample period.
Events that are shorter in duration than the period between
sampling can potentially be missed. For this reason the sample
period should be chosen to be at least twice the fastest event rate
(e.g. An event being monitored is expected to occur no faster than once
per minute. The sample period should then be set to at least every 30
seconds).
An event starts when the input goes low and ends when the input goes
high. For contact closure this would be when the contact is closed and
then opened. The logger records the time the event started and the dura-
tion of the event. The accuracy of the start time and duration is limited to
the rate at which the inputs are tested (as defined by the sample period).
An option to invert the displayed graph is available in the scales tab of
the instrument configuration window. This allows for setting the display
to show a high as a low for all inputs. This is the default state and will be
shown as normally low until an event occurs.
As mentioned, events start and end when the input goes low and
when it goes high (regardless of the graph invert option). For voltage
measurements this is when the voltage drops below 0.7V and goes above
0.8V. For contact (relay) closures this is when the contact closes and when
it opens. Overload will be displayed when the input rises above 5.5V.
The logger will store on event, which means that if there is no change at
the input of the instrument, it will not store any data until the next event
cycle occurs. This happens when the instrument sees the changes at an
input, as previously described.
If the expected event rate is 1s, then it would be necessary to set the
sample rate faster than once per second in order to capture the events.
As mentioned previously, the timing accuracy of the captured event is
dependent on the sample rate. The faster the sample rate, the higher the
timing accuracy.
Minimum duration of an event will need to be the duration of the sample
rate such that if the sample rate is 125mS, then the pulse will need to be at
least 125mS to be certain that the logger will capture the event.
35
Simple Logger II Series
®