Just what the title says; I'm playing with simple beginner circuits, signal amplifiers and stuff. Without fancy laboratory equipment such as an oscilloscope, how should I test the output signal is amplified ?


1 Answer 1


An Oscilloscope and multimeter is standard for electronics work, and not regarded as fancy laboratory equipment.
You can pick a second hand analogue scope up on eBay for a few dollars which will make your life a lot easier.

To answer the question though, if your signals are audio then one easy way of testing is a small speaker/pair of headphones. If loading is a problem you can rig up a little fet amplifier.
Another option would be a bulb of some sort, a VU meter, etc. A multimeter on AC will give some indication of signal level (maybe not so accurate depending on quality of meter and signal frequencies.

One cheap solution is to use a sound card and some free scope software. This will only be good for AC frequencies between ~20Hz to 20kHz (possibly a bit higher depending on sound card) but is certainly better than no scope at all.

Visual Analyzer is a pretty good example of such a tool. If you hack together a probe of some sort (e.g. stereo headphone leads with shield and signal for right left channel = 2 probes)
The sound card input will probably only be good for up to around 2 or 3 volts, but a small opamp circuit can be used to divide/amplify and make it usable over a greater input range if necessary. I think there is an example circuit given to use with the software at the link above.

  • \$\begingroup\$ Great link! (+: eBay India doesn't carry oscilloscopes as yet, and local markets charge a hefty premium ... which is why it is deemed fancy hereabouts. I'm looking to amplify the output from a load-cell using a 741 (because stuff like the INA123/333 AD???) are again unknown )+: \$\endgroup\$
    – Everyone
    Dec 9, 2011 at 9:47
  • \$\begingroup\$ Agreed. Not having an oscilloscope working with electronics is almost like eating without being able to open your mouth. It's not fancy, almost necessary. \$\endgroup\$
    – kenny
    Dec 9, 2011 at 10:48
  • \$\begingroup\$ @Oli Glaser Hi! I've seen you recommend Visual Analyzer several times on this site before so I'd like to ask you hot to actually enable the oscilloscope mode there? When I download it, the oscilloscope and spectrum analyzer functions are grayed out. \$\endgroup\$
    – AndrejaKo
    Dec 9, 2011 at 11:42
  • \$\begingroup\$ @AndrejaKo - I'm not sure, it worked for me first time (on a few different computers) IIRC. I do remember having to select the correct input device in the Settings->Device tab and make sure the sample rate/resolution was right. I just tried disabling my input and I got some error messages about "no input device" but nothing greyed out. I expect it's something to do with your sound card/VA settings, try a few different settings. It's also possible it's a driver issue - maybe send the Author a mail if you can't get it working as he should know what is likely to be supported. \$\endgroup\$
    – Oli Glaser
    Dec 9, 2011 at 13:11
  • \$\begingroup\$ @Oli Glaser OK, thanks! My soundcard is working fine with other oscilloscope programs and in VA I can see the waveform, I just can't get the oscilloscope mode to show up. In the end, I'll most likely mil the author. \$\endgroup\$
    – AndrejaKo
    Dec 9, 2011 at 13:43

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