User Manual

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Exercise:
Press and hold the upper right hand button, to enter the menu.
Release and press again a number of times until ‘Trg Level’ is
highlighted. Wait until unit quits the menu.
Now look at the bottom left hand side of the screen, the trigger
symbol is displayed.
The arrow buttons allow you to shift the trigger level up or
down. Check out what happens if you move it al the way down.
At a certain point, the waveform becomes unstable and starts
scrolling from right to left. If you look closely, this happens when
the trigger point is shifted below the bottom of the waveform.
If you shift it up again, so that the trigger point is located between the bottom and the top of the wave-
form, it will be stable again.
It is even possible to use the trigger setting to exactly determine the point where the scope will trigger.
Try moving the trigger gap up and down between the top and bottom of the waveform. The waveform
will shift horizontally in such a way that that the beginning of the trace corresponds with the trigger level.
What is the purpose of the ‘slope’-symbol?
Let’s change the slope and see what happens. Press and hold the upper right button to enter the
menu. Release the button and press it a number of times until ‘Slope’ is highlighted. Wait for the
unit to exit he menu. Now look at the bottom left hand side of the screen, the slope symbol is dis-
played. Press any arrow key to toggle between rising and falling slope. Take a look at the waveform
and see what happens.
So the slope setting also determines where the scope will trigger. This can be on the rising or on the
falling slope of the signal.
Experiment 8: Waveform with adjustable
frequency
Connection layout:
Connection summary:
GND clip : 4
Probe tip : 9
Purpose:
The purpose of this experiment is to demonstrate the use of the ‘trigger’-function.
How?:
1. Place the probe switch “x1/x10” to ‘x1’.
2. Flip SW1 into the ‘full wave’-position.
3. Turn on the HPS140 Handheld Pocket Scope, it will turn on in ‘auto-setup’ mode.
Select DC coupling.
Set unit to 10ms/div and 2V/div. Adjust RV2 and RV3 in such
a way that the waveform looks like the the screenshot below.
The unit displays a square wave. The rising edge of the square
wave is not perfectly ‘square’, due to the limitations of this simple
two-transistorcircuit.Anyway,theresultingwaveformisnefor
our experiment.
As you can see, the displayed waveform is perfectly stable, it does not jump from left to right.
The circuit responsible for this is the triggering circuit.
How does it work?
Take a close look at the left hand side of the screen, where the waveform
starts. You will see a vertical line with a small ‘gap’. In this gap, a ‘slope’-
symbol is displayed. This ‘gap’ determines the trigger point, the place where
the scope will ‘trigger’ or will start drawing the waveform on the screen.
NOTES:
Waveform with adjustable frequency Waveform with adjustable frequency
rising slope
falling slope
Conclusion: Trigger- and slope settings allow us to get a stable signal and make it
easier for us to study parts of a complex signal.
We encourage you to further experiment with your oscilloscope. Try looking at vari-
ous signals from all kinds of sources. Just make sure that you respect the maximum
input voltage of your scope (100Vp with probe set to x1). If in doubt, begin by setting
the probe to x10. We do not encourage you perform measurements on ‘live’ equip-
ment, i.e. equipment that is connected to the power grid, without a transformer.
These circuits are unsafe. Examples of unsafe circuits are: some household appli-
ances, old TV sets, dimmer circuits, switch mode power supplies, etc. Battery oper-
ated equipment is usually safe.