Hi Didier, Thanks for the idea. I haven't done any 8051 programming, but the price is great and you list other advantages on your web site. I appreciate the recommendation.
Kevin > A cheap way to measure temperature that will also be a good learning exercise > would be to use a Silabs Toolstick. Most of their chips have a built in > temperature sensor and a demo ADC program that spits out the temperature over > the serial port emulated USB interface. > > The toolsticks are all about $10 and you need a Base Adapter that is $15 I > believe. The tools are free (demo, size limited Keil compiler, or the free > unlimited SDCC) > > More info on my web site in the Wiki > > http://www.ko4bb.com > > Alternately, you can buy a USB temperature sensor on eBay for about $10 I > believe, but you won't learn much by using it... > > Didier KO4BB > > Sent from my BlackBerry Wireless thingy while I do other things... > > -----Original Message----- > From: Kevin Rosenberg <ke...@rosenberg.net> > Sender: time-nuts-boun...@febo.com > Date: Tue, 4 Oct 2011 09:03:56 > To: Discussion of precise time and frequency measurement<time-nuts@febo.com> > Reply-To: Discussion of precise time and frequency measurement > <time-nuts@febo.com> > Subject: Re: [time-nuts] [Solved] Looking for multiple PPS timestamp logging > > On Oct 4, 2011, at 4:36 AM, Hal Murray wrote: >> In California, the diurnal temperature swings are big enough to be useful. :) > > Here in New Mexico as well, useful or ruinous depending upon your application. > Hence, I believe, your smiley face above ;) > >> The swing would be much bigger outside, especially with an open sky. > > We thought about an outdoor light and temperature sensor when my son > considered measuring the stability of the PPS signal from a NetClock/2 > WWVB receiver. But, we'll be measuring the temperature near the indoor XO. > >> I was thinking of keeping track of when you expected each pulse to arrive >> next and sleeping until a little before you expected the soonest one. >> (Adjust "a little" by trial and error.) > > Sure, and the solution becomes more interesting the more pulse lines that > are being polled. > >> I agree that Tom's picPET will be a fine way to do it. I was just playing >> with how to do it with the parallel port. > > I lot of fine ideas come from thought experiments. > >> It's still an interesting question of how accurate you need to measure the >> time. That's probably a good one to work through with your son on the back >> of an envelope. > > I think so, too. So, my son will be learning more about stability, Allan > deviations, modified Allan deviations (which should be more useful for > the number of averaging points over a month), and improving his exponent > skills. > > Another statistic he'll be learning is the Pearson correlation coefficient > to compare temperature (probably in Kelvin) to the XO frequency. The more > precisely those are measured, the more likely the Pearson will reflect the > true correlation. > >> How are you measuring temperature? > > Good question, because we haven't completely solved that. We'll be using > a LM35CAH mounted next to the 32768 crystal and measuring the > voltage once a second. > > What I haven't decided is whether to have my son use the 34401A and GPIB > polling via a Prologix adapter versus a simple MCU firmware using a 2.5V > reference voltage and a 10-12 bit ADC and outputs the ADC result either > once a second, or in response to a pulse (probably from the PPS of the XO). > The first has merits of accuracy and simplicity, but I prefer he use > more affordable devices than the 34401A in his experiment to even his > project compared with other students. The latter has the advantage of > price, but the disadvantage of me writing the firmware (though, the > firmware is almost trivial). But again, I'd like him to be as > independent as possible. > > So, if you know of any simple ADC to UART firmwares available, that'd > be great so he can just reference someone else's code. The picPET > is a perfect device at the perfect time. But, we can't rely on tvb > to come up with a 'picADC' at a similarly serendipitous time. > > Kevin > > > _______________________________________________ > 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. > _______________________________________________ > 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. _______________________________________________ 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.