); SAEximRunCond expanded to false Errors-To: [EMAIL PROTECTED] RETRY On Tue, 06 Nov 2007 11:57:27 +0000, Joe McElvenney <[EMAIL PROTECTED]> 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! _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
