16
Chapter 1 TriLog
Note:
Sampling at a rate slower than the expected rate can cause
"frequency aliasing". In such a case, the graph will show a
frequency much lower than expected. In Figure 4 below, the higher
frequency sine wave was sampled at 1/3 of its frequency.
Connecting the sampled points yielded a graph with a lower,
incorrect frequency.
Figure 4: Frequency Aliasing
Manual
sampling - use this mode for:
•
Recordings or measurements that are not related to time.
•
Situations in which you have to stop recording data after each
sample obtained, in order to change your location, or any other
logging parameter (Note: During the experiment NO CHANGES
can be made to the TriLog
’
s configuration).
To start an experiment using manual data logging, set the
RATE
to
“
manual
”
and
press the
Run
button once to start the data recording, then press the
Samples
button each time you want to collect a sample.
2.Sampling Points
After you have chosen the sampling rate, choosing the number of points will
determine the logging period: Samples / Rate = Logging time. You can also choose
the duration of an experiment first, and then calculate the number of samples:
Samples = Logging time
×
Rate.
Continuous
In the Continuous mode, TriLog does not save data, and can continue logging
indefinitely.
If TriLog is connected to the PC and the MultiLab software is running, the data is
automatically transferred to the computer and displayed in a real time graph.
To operate in Continuous mode select
RATE
equal to or less than 100/s and
SAMPLES
=
Continuous
.
You can also select Continuous mode directly from the MultiLab software.
