As an electronics enthusiast or a hobbyist, you probably yearn for an oscilloscope to check out those elusive waveforms in your amplifier or radio. However, the cost deters you. A reasonably good oscilloscope will set you back by several hundred dollars, unless you buy a pre-owned piece or get one at the flea market.
However, there is hope yet. As you probably own a PC, all the hardware needed to display waveforms is already available to you.
Using PC Like an Oscilloscope
What you now require is software that will enable your PC to work as an oscilloscope; you can purchase this from Zelscope. If you own a PC with a fast processor, about 1GB RAM, about 1MB of free Hard disk space, and at least one 32-bit sound card, you are set up for converting your PC into an oscilloscope. You can even use your PC as a Spectrum Analyzer.
Some additional front-end hardware will be required to attach the oscilloscope probes and feed the test signal into the PC.
You can build your own following the instructions on the Zelscope site, or buy the front-end ready-made. Ordinary RG-58 coaxial cables can be used to make up the probes.
The probe end of the coaxial cable can have crocodile clips, while the end of the coaxial cable that connects to the front-end electronics could be terminated by a BNC.
There is a lot you can do with such a simple arrangement. You get up to two traces with a bandwidth of 10Hz to 20KHz, a sampling rate of 11KHz to 44KHz and an 8- to 16-bit acquisition (it all depends on your sound card).
The time base is from 5Sec to 10uSec with adjustable triggers, two independent cursors, direct frequency readout and time and voltage difference readouts.
The Zelscope-and-PC combination as a low-cost oscilloscope can help adjust audio circuits, take measurements in physics experiments, tune musical instruments, troubleshoot digital circuits, and do many other things. One limitation is that you cannot sense or display DC waveforms, since the sound card of the PC is capacitively coupled.
The spectrum analyzer mode can display amplitude and/or phase.
Apart from the display of waveforms, you can save screenshots, copy-paste functions for data files, save visible traces as text files and make printouts.
Your PC can now be used as a data logger as well. What if you are not satisfied with just an oscilloscope or spectrum analyzer in your arsenal?
Maybe you like to add a waveform generator and a ZRLC meter as well - for which you will need the Visual Analyzer. For those who are looking for something more professional, and willing to spend, Pico has a plethora of similar gadgets.
Dayo says
Hi Swagtagam, I used zelscope as described here, but I didn’t get the sinusoidal waveform with the utility supply, it is like triangle wave when I put the wave sequence on hold.
Swag says
Hi Dayo, sorry I cannot troubleshoot it since I have not tried it yet…I would recommend buying any basic smallest oscilloscope, instead of relying on other forms of alternative.
Abu-Hafss says
Hi Swagatam
I am planning to buy a used analog oscilloscope.
Can you guide me what to check/how to check if the unit is fully working and it is trouble free.
Swagatam says
Hi Abu-Hafss,
Although my last use of oscilloscope was way back in 2001, after that I got busy with my manufacturing job, i'll try to recollect my memories and assist you as far as possible.
Abu-Hafss says
Hi Swagatam
Being a hobbyist, I feel the need of having an oscilloscope. Since long time I have been reading comments of various people. Most of the experienced fellows prefer to have a used analog scope as compared to brand new USB scopes. I have a budget of less than 100$, what do you suggest?
Abu-Hafss says
In my place I can get a used 25MHz, 2-Channel Analog scope for $50-70 depending upon the condition.
I had checked the poor man's oscilloscope long time ago. It can be used where the voltage is 2V or below. So I think it is useless for me.
My actual question was your suggestion between a used analog scope and a USB scope which can measure frequency.
Swagatam says
A USB scope can be more advanced than an analogue type.
In the poor mans method the 2V can be easily scaled down and it provides an excellent option to check waveform cheaply yet accurately…
Abu-Hafss says
Is it possible to view a wave with a magnitude of 30V in poor man's scope?
Swagatam says
yes by using a voltage divider stage…..it would be like hearing music at a lower volume
Anonymous says
hi, how c i test inverter welder output waves? They are high frequency right? Thx.
eign says
good day sir you mean that the energy saving device that show on the market also in you tube that plug-in to your convenience outlet and its says that you can reduce the amount of current that is flow in the entire house to be reduced is not true?
Anonymous says
Dear Swagatam,
I am first time taking part in your valuable blog. I have an Analog Oscilloscope of 60 MHz. It is time consuming to calculate the frequency. Is there any way (like Circuit) I get frequency in digital. Kindly help me in this regard. Thanks
Mubashir
Karachi, Pakistan
Swagatam says
Dear Mubashir,
Digital circuit will be complicated to make, you may try an analogue design as shown here, it's very accurate:
https://homemade-circuits.com/2011/12/how-to-build-inexpensive-frequency.html
EIGN says
good day sir how about the energy saving device that sell in the market do you have a diagram? thanks again for your reply. by the way i'm EIGN from philippines
Anonymous says
good day sir! can you design a circuit to reverse the flow of household current meter? thanks