DMM question?

Sure it can. The threshold-crossing rate of Gaussian noise with any spectrum you like can be calculated easily, and for any given amplitude you can back out the mean frequency. I use that equivalence routinely for threshold-setting.

Cheers

Phil Hobbs

Would that have been Peter Fisk, by chance? He was head of the NMI until a year or so ago, but he was the head honcho for Australia's time and frequency standards. The NMI's atomic clock is one of the top-tier clocks in determining UTC.

Peter's grand-father Ernest was the radio amateur (and managing director of AWA) who received the first direct radio transmission from the UK to Australia in 1918, a message to the nation from our then PM Billy Hughes.

Peter is the reason we moved to Sydney.

Clifford Heath.

------------------------- Phil Allison

** Frequency is not the point here.

Fuzzy thinking was.

...... Phil

Having a point is kind of restrictive, isn't it?

-----------------------------------

** No.

The engineer's name was Colin. His "degree" was from the UTS.

He was also unaware that resistivity is measured by comparing samples of metal with the same cross section. Not the same weight.

..... Phil

John Larkin wrote: ===============

** Only if you are demented like Bill S.

It doesn't seem to restrict our resident qullible twits.

Phil can only dream of being as demented as I am - which is not in the least demented, but he's much too demented to realise this. Senile dementia is what he presumably what he has in whatever passes for his mind, but there are lots of other ways of getting your brain too messed up to work well, and taking right-wing political propaganda too seriously is a remarkably popular route.

I'm demented, but surely nothing like Sloman.

John Larkin's dementia is most obvious when he goes in for climate change denial. That makes him a gullible twit.

I'm fairly that I'm not that kind of gullible twit - and I've not got a Jame Arthur around to spoon feed me climate change denial an other right-wing political propaganda.

I could be as far gone as Fred Bloggs seems to be - and he does think that I've got to be demented to disagree with him - but I do hang around with real people who don't seem to have any enthusiasm for getting me to get myself run through the dementia check-list.

TCR is interesting since the dimensions change with temperature.

Spehro Pefhany wrote: ---------------------------------

** How f****ng pedantic.

Resistivity is speced at a given temp. TCR with a given sample.

..... Phil

Zero crossings don't mean much if you don't high-pass filter a completely random noise, but I was more concerned with... for instance, a bell tone. Several harmonics, with lower ones dominating at the end of the time sample, and higher ones in the beginning.

I once saw a music spectrum with so many spikes, I declared it had to be a fake: no orchestra has that many instruments. It was Pink Floyd, 'Bells'.

whitless 3rdwit wrote: ==================

** Wanna try that song title again ?

...... Phil

YCLIU. It's a theorem of Rice's from 1944.

Bells and gongs and drums don't have harmonic spectra. Each mode produces a pure tone, but because the modes aren't equally spaced, instead of 'mmmmmmm' you get 'bong' or 'Tshhnnnng' or 'thump'.

You have do decide what frequency you're interested in, because the different components have different discrete frequencies. (I suspect that's what you were getting at.)

See above.

Cheers

Phil Hobbs

If there's a frequency distribution with a peak, you mean? But really white noise doesn't have a peak.

Cylinders or bell-shaped bells with a clapper DO have harmonic spectra, with standing waves around the circumference. The modes are more complex with steel drums or gongs or even jingle bells, which are struck in different places.

Yeah, my bad; the title is 'Time', from The Dark Side of the Moon...

---------------------

** Yep - near blows you ears off played loud on a good stereo.

...... Phil

Don't know about that, but historically, HP used reference multiplier techniques to get more counter resolution, eg: 10MHz -> 500 MHz. Also, have a look for the 5359A time synthesiser, which used an internal

10MHz ovenised reference to get stable pS output resolution. Old HP Tech Journal is full of descriptions of how they designed such kit, late 1970's / 1980's...

Related to that, one part in 10e7 is not that special, just the usual HP prowess. Reciprocal counting and digital processing in the mix...

Chris