Max hold option feature req

Hello Matt,
I have an QA403, great device, really enjoying working with it. I investigate an “popcorn noise” on an audio amplifier, so i think an option on FFT for max hold will be useful to trace the problem. Because that “popcorn noise” appear absolutely random, without this option its very hard to trace.
Also, an FFT split screen (L and R) will be useful too.
Best regards,
Sorin Baicus

I second your motion, Sorin!

Yes, agree this would be good to have. Probably there will be two buttons added to the Acquisition group. One would be AVG and the other would be PEAK. If both are off, then it would be normal operation. If AVG is pressed, then it will function as today when averaging is non-zero. If PEAK is pressed, then it will function as peak detect. Does it make sense to have the ability to indicate the number of cycles for which to accumulate the peak? For example, maybe you select peak hold that examines the peaks of the last 10 or 50 cycles. This will probably be a few releases out, but agree it would be useful addition.

If you had the ability to know # of cycles for the peak, that would be awesome. However, in all my years of using expensive HP/Agilent/Keysight RF spec ans with peak hold, none of them told you how many cycles were used. A great feature, though!

Thank you Matt for your positive response. PEAK hold “forever” will be what i need right now. But ability to set an 100 cycle PEAK will be uselfull too.
Best regards,
Sorin Baicus

Hi Matt, any news?
Regards!

Hi @bmsorin, I think the path for max hold is know, but it will require a front-panel UI change and those tend to get queued up all at once because new artwork needs other changes. Hopefully soon.

Thank you Matt!
Best regards!

Hi Matt,
Any news about this option?
Best Regards!

Hi,

I have had a QA403 for a few weeks now and I am doing measurements with noise.
What I really miss is a peak hold function and this is still not available in the software version v1.193.

Searching the forum, I saw that the last one asking for it is over a year old…
Is this feature still going to be available for the QA403?

Kind regards
Bram

Hi @Bram, yes, peak hold is a work item that will tear up a fair bit of UI and so it will probably continue to be put off until something forces that.

BTW, I get the reason for peak hold in RF where you are looking for momentary events so that you can zero in on those and then use a quasi-peak filter and real time block down conversion to understand emissions. But what is the purpose you see for audio? A peak hold will probably over-estimate noise by 10 dB. You can see this by looking at noise in loopback at 42 dBV full scale input. Take look at the plot below. It’s average 50 times. You can see the noise at 1k is around -105 dBV.

Now, I turn off averaging and do a single cycle run (control+space) over and over until I see a peak around 1 kHz. Take a look around 850 Hz, that’s around -97 dBV.

And here’s another. This time, take a look around 1400 Hz, that’s around -95 dBV.

So, if you enable peak hold and let it run, it will converge to a result that has relation to the real average. If you wait long enough, you could probably see the peak line approach 15 dB worse than the average.

What measurements are you seeing the need for this?

Hi Matt, :slight_smile:

Why do you think I use the QA403 for Audio? grin

I am currently designing a noise source from about 5Hz to 10MHz and then trying to get it flat within 0.5dB or better across the entire bandwidth.

The higher part of the bandwidth I can evaluate with my spectrum analyzer, but most spectrum analyzers are not good in the bit of frequency range that the QA403 can perform well.

The power supply for the noise source must come from battery power, otherwise I can use the noise function of one of my function generators.

The development is still in the early stages but with a standard 12V Zener I am already pretty much in the right direction.

So it would help if the Peak Hold feature were available.

I already tried the “Averages” yesterday on the QA403

Anyway thanks for the quick reply!

Look how your baby is doing…

I hooked up the QA403 to my Audio Precision Portable One as a Sine source and then checked what is approximately the optimum level to get the lowest possible THD, see the picture, not bad! :slight_smile:

Kind regards,

Bram

I’m working with noise sources as well. Ideally you need to map both the frequency distribution and the amplitude distribution. The noise sources I have (GR and Quan-Tech) both use noise diodes/zener diode and down convert from 30 MHz to audio to get uniform noise levels. Its involved but works well.
Maybe there is a way to export the samples and analyze them for level distribution with some other software? Matlab?