Delayed (Bluetooth) Distortion measurement

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dri66
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Delayed (Bluetooth) Distortion measurement

Post by dri66 » Mon Jun 10, 2019 9:54 am

Hello,

For service purpose we need to setup an easy way to compare a sound or sweep,for some Bluetooth devices.
The chanlenge is that we will have a latency between the input and the output.
Do you have a product that can delay one of the inputs so we can measure the differences between both signals and maybe directly see if we have a distortion ?

Thank you in advance for your help.

PS: Do you have some microphones that you recomand to connect to your devices ?

Best Regards,
Didier Ribbens

Gerry
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Re: Delayed (Bluetooth) Distortion measurement

Post by Gerry » Thu Jun 13, 2019 11:23 am

Hi Didier,

You can use one of our PicoScopes to do this. If the waveforms overlap (i.e. there is no gap between the end of the first and the start of the second) then you can just use a Timebase long enough to capture both waveforms, and then align the 1st waveform with the second using a Math channel with a positive Time offset. If there is a gap between the waveforms then you can either use the same technique as before, or you can use a split buffer to capture the 2 waveforms with a trigger at (or near) their start, and then create a reference waveform out of one of them to load over the top of the 2nd waveform (note that, with any of these comparisons you can also auto arrange the axes so that one waveform is above the other, as in the shown in the screenshot below:).
Comparing delayed waveforms.png
If you are looking for distortion in the frequency domain, then you can also use the described methods on a Spectrum plot.

If you are comparing audio frequencies then I would recommend using an audio mic. If they include high frequency modulation, then an instrumentation mic would be a better alternative.

Regards,

Gerry
Gerry
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bennog
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Re: Delayed (Bluetooth) Distortion measurement

Post by bennog » Thu Jun 13, 2019 12:52 pm

If you want to make a bodeplot look at this thread.

bodeplot

Don't know houw it handles the BT delay, but it is including source so you can hack it in yourselves.
Be aware if you want to do this you need a scope with builtin signal generator.

Benno

dri66
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Re: Delayed (Bluetooth) Distortion measurement

Post by dri66 » Thu Jun 20, 2019 6:58 am

Hello,

Thank you for your prompt reply.

Any model that you can recommend ?

Best Regards,
Didier

Gerry
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Re: Delayed (Bluetooth) Distortion measurement

Post by Gerry » Mon Jun 24, 2019 9:26 am

Hi Didier,

The Model of PicoScope that would be best for your application (at the lowest cost) will depend upon the smallest distortion that you need to see, along with the length of the delay between the input and output. So, if you have an idea of the level of distortion that you would like to detect (relative to the amplitude of the largest sound you are likely to capture) and the latency (approximately) we can suggest a model to look at.

Regards,

Gerry
Gerry
Technical Specialist

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