Hi, Wrote:No, the temperature is not stable, not even close.
Wrote:Given that the TL431 is quite good at measuring temperature, that makes itunsuitable in this case. Wrote:There is a LOT more to making a good temperature-controlled >environmentthan hacking together a DIY oven. Thatmay be fine for stability of tenths of a percent (10e-3), but when stability of >10e-13is at issue it doesn't pay to start with 50ppm parts and put them in a >DIYoven. You need to start with low-tempcoparts. Waita second good people! We have a bit of confusion about what I wrote. Anamplification of what I wrote: TheTL 431 is listed as a low noise shunt regulator. It doesn’t measure temperature at all. Theonly noise spec I could find is about 7 uV. A LM723 data sheet specified 2.5 uV noise. The REF 012A specifies 5 uVnoise. The first two are around 50 cents from Mouser. The REF102A is about 10X more. I’mnot sure the original reference diode had that low noise but that’s a guess onmy part. Thetemperature circuit I referenced uses a 220 ohm load resistor in series withthe positive output of the regulator and Vcc. The temperature is regulated by a resistor from Vcc to the programminglead. Then there is a thermistor going from the programming lead to ground. Usingthe formula given in the data sheet. One can then calculate the desired voltageratio and then with a series control pot set the temp to the desired value. Thisis a simple circuit and with 1% 100ppm vishey metal film resistors it would begood for .1 degree stability. That should suffice for Paul’s application Charlesis correct that if one is getting into the TN class of .01 or .001 degreestability a far more elaborate circuit is required. Goingback to my original post, this was only a suggestion for an inexpensivesolution for the problem. Since I don’t have a 5065A, I can’t prove or disproveif it would give the desired results. WhenI get them set up, my demon to solve is how to get my 5370B’s to be cool andquiet. There has to be a better solution to the PS heat. Regards, Perrier _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
