DMM frequency response test results

[amb]

I made this post on headwize which may be of interest to head-fi DIYers who don't frequent headwize often.

 

[lini]

Interesting read. I'm actually quite surprised that even the cheaper models do fairly well in the audible band, even if not in all ranges... I've got a question though, as I didn't find that mentioned: What signal level were you actually using for each range? Oh, and what waveform - sine?

Greetings from Munich!

Manfred / lini

P.S.: And thanks for the reminder, btw. I really don't visit good, old mother HeadWize often enough...

 

[amb]

I used sine wave, 100mV for the mV range, and 1V for the higher ranges.

 

[Fresno Bob]

Really nice post and all. So what does this it all mean?

 

[amb]

Quote:

Originally Posted by Fresno Bob /img/forum/go_quote.gif Really nice post and all. So what does this it all mean?

I thought the last paragraph in my post sums it up...

 

[SiBurning]

I should probably register over there, but...

Not exactly sure what you're testing. It's confusing because you mention the low noise measurement preamp.

Assuming you're just recording what's measured at different frequencies... Do you have some kind of control to measure against? Are you trusting your function generator to generate a stable voltage at all frequencies, or are you doing some kind of second measurement for comparison, which begs the question... what's the response of that measurement instrument?

This is a cool test. Makes me want to test my equipment. Only I don't know which parts to trust.

 

[amb]

Quote:

Originally Posted by SiBurning /img/forum/go_quote.gif Not exactly sure what you're testing. It's confusing because you mention the low noise measurement preamp.

It's in relationship to this post I made on headwize about measuring the noise of PSUs. I think you'll see why that led to this test.

Quote:

Assuming you're just recording what's measured at different frequencies... Do you have some kind of control to measure against? Are you trusting your function generator to generate a stable voltage at all frequencies, or are you doing some kind of second measurement for comparison, which begs the question... what's the response of that measurement instrument?

Yes, as the title suggests, I'm measuring the frequency response of the DMMs I have. Of course, it assumes that the function generator has a flat response too (i.e., outputs the same voltage over the entire range of frequencies of interest). I had verified this to be true with several oscilloscopes, a couple of which have bandwidth up to 100MHz.

Quote:

This is a cool test. Makes me want to test my equipment. Only I don't know which parts to trust.

Yep, a wideband scope should be very trustworthy.

 

[DaKi][er]

I need a good function generator

It'd be nice to see what my HP3456A does, if only for bragging rights