User Manual
Table Of Contents
- Getting started
- Oscilloscope basics
- Analog versus digital:
- Waveforms:
- Measuring probe:
- Connecting the probe:
- Setting up the board:
- Experiment 1: Measuring AC voltage
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- What we see:
- Experiment 2: Adjustable AC voltage
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- Experiment 3: Measuring AC grid frequency and period
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- Experiment 4: Rectified AC, single phase
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- A little theory:
- Experiment 5: Rectified AC, dual phase
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- A little theory:
- Exercise:
- Experiment 6: Smoothed versus unsmoothed DC (ripple)
- Connection layout:
- Connection summary:
- Purpose:
- A little theory:
- How?:
- Experiment 7: DC measurement
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- Exercise:
- Experiment 8: Waveform with adjustable frequency
- Connection layout:
- Connection summary:
- Purpose:
- How?:
- How does it work?
- Exercise:
- What is the purpose of the ‘slope’-symbol?
16 17
Experiment 7:
DC measurement
Connection layout:
Connection summary:
GND clip : 4
Probe tip : 6
Purpose:
The purpose of this experiment is to show that a scope is also suited to measure DC voltages.
Ingeneral,scopesareusedtomeasureACvoltages.ForDCvoltages,amultimeterisne.However,if
you don’t have a multimeter at hand, you can still perform DC measurements with a scope.
make sure the scope is set up correctLy for dc measurements
How?:
1. Place the probe switch “x1/x10” to ‘x1’.
2. Turn on the HPS140 Handheld Pocket Scope, it will turn on in ‘auto-set’ mode.
‘Auto setup’ will also work for DC measurements.
There are 3 important settings that need to be performed for correct DC measurement:
• DC input coupling
• DC readout
• DC reference
DC input coupling:
Input coupling needs to be set to DC (=). When set to AC, the scope will block any DC signal, so we
won’t be able to perform DC measurements. At start-up, the unit is automatically set to DC coupling.
Next, we will set the readout in the bottom right hand corner to DC.
Press and hold the upper right hand button until the menu appears.
Release the button and press it again a number of times until the
‘readout’ setting is highlighted
(123 appears in the lower left hand corner).
Next, press any of the arrow keys repeatedly until Vdc is displayed.
Wait for the unit to return to scope screen.
It now displays the measured DC voltage in the lower right hand
corner.
NOTES:
DC measurement
Set the DC reference:
To set the DC reference, set the input coupling to GND and
wait a couple of seconds, until the DC readout in the lower right
hand corner displays ‘0.0mV’.
If the settings have been performed correctly, your scope will
nowshowaattraceabovethecentreofthescreenandthe
readout in the bottom right hand corner will show the measured
DC voltage.
Don’t forget to switch it back to ‘DC coupling’ again.
Exercise:
If you move the probe clip to test point 7 or test point 8, you will notice that the scope will automati-
cally adapt the V/div setting and the measured DC voltage will drop to 2/3 or 1/3 of the original value,
because of the resistor divider R2/R3/R6.
What happens if you swap the probe tip and ground clip?
Probe tip to test point 4,
ground clip to test point 6
The trace jumps from above the centre of the screen to below
centre, and the readout shows the same value, but negative.
This is logical, as the ground clip is the ground or (-) and the
probe clip is the positive of our instrument. Test point 4 is at
ground level while test point 6 is positive, so we get a negative
readout.
DC measurement
Testpoint 7
Testpoint 8