Measuring harmonic distortion
Measuring harmonic distortion
(OP)
Hello,
I'm looking for instruments for measuring harmonic distortion. I have looked at the Fluke 43 Power Quality Analyzer, but it is pretty pricey. I have also considered buying a good digital scope with storage. If I could import the waveform data into Matlab, I could do an FFT and get the same results as the Fluke, and I'd have an oscilloscope. Does anybody have any other methods or meters that they use for measuring harmonic distortion?
thanks,
Andy
I'm looking for instruments for measuring harmonic distortion. I have looked at the Fluke 43 Power Quality Analyzer, but it is pretty pricey. I have also considered buying a good digital scope with storage. If I could import the waveform data into Matlab, I could do an FFT and get the same results as the Fluke, and I'd have an oscilloscope. Does anybody have any other methods or meters that they use for measuring harmonic distortion?
thanks,
Andy





RE: Measuring harmonic distortion
If you do it to learn or for research, then most techniques are good. Even using the microphone input on a PC works. Or lots of low cost USB data takers. You need to make sure that the microphone input of the PC does not have a lower frequency that blocks power frequencies.
Not too long time ago, people even used a camera to take a screen shot from an oscilloscope, enlarged it and took data points manually. Often also did a manual fourier transform. Took some time, but worked. At least for higher level harmonics.
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Measuring harmonic distortion
Another instrument I've found useful is a spectrum analyser with an extended low frequency response. HP's 3561A and 3562A dynamic signal analysers are good value although they certainly aren't cheap even on the surplus market.
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If we learn from our mistakes I'm getting a great education!
RE: Measuring harmonic distortion
Another option to consider is a Tek TPS2000 scope with the "power bundle".
h
RE: Measuring harmonic distortion
Thanks again for your inputs.
RE: Measuring harmonic distortion
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If we learn from our mistakes I'm getting a great education!
RE: Measuring harmonic distortion
RE: Measuring harmonic distortion
Your best bet is to get demo instruments from a Tek and Agilent distributor and see if you actually like the user interface and so on as well as whether it will make the measurements you need. You're looking at a fair amount of money so you have every right to ask for a trial period.
Personally I would not directly connect the TPS scope to a 480V circuit - in my opinion the inputs are not protected heavily enough for direct connection to an industrial power circuit. You might be pushing the limits of the isolation too, I haven't got the spec in front of me.
From experience I know I was pretty unhappy when the steam turbine's excitation system blew my isolation probe to bits; I would likely have been crying (or fired!) if it took out the scope. The two other lessons learned that day were to replace the crappy leads on the isolation probe with a set of HRC fused multimeter leads, and the value of having a piece of earthed sheet steel between you and it.
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If we learn from our mistakes I'm getting a great education!
RE: Measuring harmonic distortion
Thus you may be able to buy an older used TDS scope and update the firmware to get FFT for a reasonable price.
John
RE: Measuring harmonic distortion
Have you looked at the auctions? With so many companies going bust there are some real bargains to be had. Worth thinking about.
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If we learn from our mistakes I'm getting a great education!
RE: Measuring harmonic distortion
Sure, it wasn't the greatest scope in the world, the software was fairly clunky, but for harmonic and power measurements it was excellent.
It has ben discontinued now for quite a few years but you may be able to pick one up around somewhwere.
RE: Measuring harmonic distortion