Velleman EDU08, Getting Started, Page: 8 / 40

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EDU08 Getting started
Measuring DC voltage: Measuring a 9V battery
First, make sure that your scope is properly calibrated.
•
Turn on the scope.
•
Connect the alligator clips to the battery. Mind the polarity.
•
Connect the red clip to the (+) of the battery and the black clip to the (-)
of the battery.
You should see something like this:
A 9V battery generates a DC voltage, that explains the flat line. Look
closely at the number of vertical divisions, the trace almost reaches the
second division and the volts/div setting is 5V/div, so the measured voltage
is a little less than 2x5V or 10V.
How much is the exact voltage supplied by our battery?
Open the menu, scroll down to Measure and select Vdc.
Leave the menu and watch the lower right hand corner:
Our 9V battery supplies 8.13VDC
Now, swap both alligator clips and check what happens: This is a nice feature
of an oscilloscope, it can measure both positive and negative DC voltages.
Displaying and measuring waveforms:
We have a nice waveform available at the test pin, it is perfect for our
measurements. Turn off the scope, connect the red alligator clip to the
‘test’-pin and turn on the scope. You should see something like this:
This is called a square wave. Note
that the complete waveform is drawn
above the center of the screen. This
is because our waveform contains not
only an AC but also a DC component:
Now, enter the menu and select ‘
AC
coupling
’ instead of ‘
AC+DC coupling
’
Now the position of the waveform changes, as the DC component of the
signal is blocked. The scope only displays the AC part, which is both posi
-
tive and negative.
Let’s measure the
frequency and period of our waveform.
First, we turn on the markers, by pressing the ‘HOLD’-button. Next, we
isolate a single period of our waveform by moving both horizontal markers
as shown below:
The lower right hand corner displays the period of our signal: 0.51ms. To
display the frequency, we select:
Now the scope will display the frequency of our signal:
Note that there are also horizontal markers available. They allow us to
measure e.g. the peak to peak value of our waveform, which is also
displayed in the lower right hand corner.
Triggering and how to use it:
Triggering helps us to get a stable trace on the screen and it also allows us
to capture events.
When ‘ AUTO Volt
’ and ‘
AUTO time
’ is enabled, the scope triggers auto
-
matically.
To enable manual triggering, select 0.1ms/div and 1V/div from the menu
and set Trigger to On:
„
LET’S MEASURE