USB multimeter or datalogger

Author
Discussion

TonyRPH

Original Poster:

12,963 posts

167 months

Thursday 26th May 2016
quotequote all
Can anyone recommend a cheap USB multimeter or datalogger.

I need AC accuracy for audio measurements (20hz - 40khz) and I'm finding the average meter doesn't fare too well above about 1khz (even my trusty old Fluke) - and besides - I'd like the USB connectivity for data logging..

Any recommendations?

Thanks.


anonymous-user

53 months

Thursday 26th May 2016
quotequote all
Sounds more like a job for a USB oscilloscope perhaps?

TonyRPH

Original Poster:

12,963 posts

167 months

Thursday 26th May 2016
quotequote all
I already have a Picoscope (2204A) and an Owon SDS (model forgotten) digital oscilloscope.

However neither of these give me the option to log the data I want.

I'm looking to get RMS voltage values over a range of frequencies, and then use this data in a spreadsheet and / or gnuplots.

I have tried various opensource scripts / programs to talk to the Owon, but the data I'm getting back is just the actual waveform data, rather than simple RMS values.

Sure, I realise I could calculate the RMS values from the waveform data, but that just complicates things!

So I'm stumped.


Jimbo965

172 posts

144 months

Friday 27th May 2016
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Lindos Minisonic is the cheapest audio analyser I know of but its about £500.

Usb scopes will probably suffer from limited dynamic range as the ADCs are normally only 8-bit.

Perhaps use the mic in on smart phone with an app like SignalScope?

Zad

12,695 posts

235 months

Friday 27th May 2016
quotequote all
Even my Tektronix DMM4020 bench meter is only guaranteed to 440Hz, which is ridiculous really. Don't forget that oscilloscopes have a gain range switch which hugely increases the effective dynamic range. You could always build yourself a precision rectifier with an op-amp and some diodes, then measure it with the Fluke on DC mV. They are usually linear to well outside the audio spectrum.

Who me ?

7,455 posts

211 months

Friday 27th May 2016
quotequote all
Have a look at the spec etc for a Fluke 187/189. Might be ore of what you are looking for at a lot less.

TonyRPH

Original Poster:

12,963 posts

167 months

Friday 27th May 2016
quotequote all
Well after much searching I found an Amprobe AM-270 which apparently is good to 20kHz on the AC ranges.

However, it has no PC connectivity, so I had to rule it out.

In any event, as Zad has suggested, I'm going to build a precision rectifier, and feed that into an old Sinometer MAS-343 that I've had for years - this meter has a serial! port and I have located some custom software that will talk to it.

Then I'll be able to log the data as required, although I have almost completed the task using pen and paper and a 'TestLab' AC millvoltmeter that I have. (I did think of trying to tap into this to get the rectified output, but I don't really want to mess about with it)

Rather tedious though!

One final thought was a PC sound card from 'M Audio' as these are supposed to be pretty good as well. I do have an old Sound Blaster Live! 24 bit external USB device, however the ADC has incredibly poor linearity (no surprise there!).

Thanks for the suggestions.