Re: noise - pp vs rms vs what you see on a scope


Eeysore wrote:


I take that back. It's spec says it is flat to 150KHz.

Exactly.

In round numbers that means your scope is seeing a level that's at least
9dB high relative to the correct measuring bandwidth.


Ok, so what about when using the built in meter? That is exactly how the
Ferrograph manual describes making a S/N measurement.


** But only for a tape recorder, with tape running - where the noise
bandwidth is self limited.


There is no bandwidth
limiting components I can see in the meter drive circuit so why doesn't
the
meter read 9dB too high as well?


** It will read circa 9 dB high for any white noise source with 200 kHz
bandwidth, or more.

You MUST check your RTS2 with an audio generator and scope for the ACTUAL
high frequency response at the low end of the 1 mV range you are taking
readings from.

The makers spec is far too vague to trust.



........ Phil


.

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