[time-nuts] OT: AC voltage standard

Brooke Clarke brooke at pacific.net
Tue Nov 6 17:15:50 UTC 2007


Hi John:

How does it compare to the Linear LTZ1000?

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Cam


Neon John wrote:
> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+brooke=pacific.net at febo.com RETRY
> 
> On Tue, 06 Nov 2007 11:57:27 +0000, Joe McElvenney <ximac at btinternet.com> wrote:
> 
> 
>>Anyone know of a simple way of producing an AC voltage standard
>>suitable for general workshop use without reference to another
>>one? About one percent would be good enough, wave shape and
>>frequency accuracy not important (wash my mouth out). I have a
>>Weston Cell for DC voltage calibration, a Rb one for frequency but
>>nothing for AC volts. Perhaps there is a chip out there that
>>clocks between accurate limits that I could use as a source?
> 
> 
> If a simple square wave will do then one of the simplest and yet most accurate
> sources is to switch a known DC reference using a mercury wetted reed relay. A dry
> reed will work but will bounce a little.  The small reed relays as were ubiquitous in
> data acquisition systems up into the 80s can switch at 150 hz or better.  Driving the
> coil of the relay with stepped-down line voltage is a good solution.
> 
> You probably know this already but I'll mention it anyway.  You can't draw any
> appreciable current from that weston cell and it remain within specs.  Even a 1 meg
> scope probe is too much.  I'd use a DC power supply or battery and a quality DVM
> (which is probably more accurate than the standard cell) instead.
> 
> I started in metrology in the time when the standard cell was the best there was.
> Boy, am I glad that era is gone.  I still have one just to stimulate old memories but
> my lab standard is a precision 10 volt reference IC.  I don't recall the part number
> but both National and Burr-Brown make 'em.  Untrimmed accuracy is something like
> 0.01%.  That's better than my boat anchor Fluke meter calibrator!
> 
> John
> --
> John De Armond
> See my website for my current email address
> http://www.neon-john.com
> http://www.johndearmond.com <-- best little blog on the net!
> Tellico Plains, Occupied TN
> Save the whales, collect the whole set!
> 
> 
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