OMC-042 / 043 / 044 Data loggers
Users
’ manual
page 23
Reference
Principle of Operation
Your Observator Instruments data logger is capable of collecting and storing data of multiple
sensors. To
accomplish this, many tasks are performed. These “tasks” are scheduled and executed on their specified
time. The timing of this process is very important and is determined by the internal scheduler. This scheduler
keeps track of all the internal states of the various tasks and assigns processor time to the different tasks.
Each task is executed on its own interval. First we explain the different intervals.
There are three different intervals:
1) Sample Interval
2) Data Log Interval
3) Send Interval
Sample interval
The sample interval is the interval at which a sample from the sensor is taken (expected). So,
measurements from sensors are done at the sample interval. The sample interval is valid ONLY when the
device is in the active state. When the data logger is in sleep-mode, the tasks, triggered by the sample
interval will NOT execute, unless they are used in aggregations (e.g. a 10 minute average, see chapter
Aggregation channels), scheduled for continuous alarm sampling, or if a pending alarm is detected and you
have set “alarm set delay” to number of samples”. So in most cases you could follow the default data log
interval to take a sample.
Data logging interval
This interval determines when a data value, obtained by the sample interval-task, is stored onto the SD-
card. This type of interval is ALWAYS valid. So, even when the data logger is in sleep-mode, it will wake
up when the Data logging Interval has reached its count.
Send Interval
The send interval determines the interval on which data is send, via the internal modem. This interval is
ALWAYS valid, even if the data logger is in sleep-mode.
Send delay
The send delay will be added to the send interval in order to delay transmissions. It is only necessary to set
when you have a lot of data loggers in the same network cell to spread the network load. Use it only if you
experience problems due to a low network capacity, or when your host server does not support enough
concurrent connections.
Example
Let’s evaluate the following settings of the data logger: