Maybe I should not be posting this on the VN list, as it is only indirectly related to volts.
Still; I have been getting some messages and feedback, with no disrespect to me, asking, if I know what I am doing. With no disrespect to the people who replied, of or on list (on the contrary, I'm grateful for feedback!): My background: I have been working for 15 years with thermal engineering and measurement techniques. I have calibrated in liquid baths, ovens, against reference probes. I have calibrated reference probes in water triple cells, and gallium melting pots, (both are ITS-90 temperature scale reference points) calibrated reference probes etc. I know it its hard to do measurements with 0.1C accuracy in real life, sometimes even 100C is very difficult, ie at very high temperatures. Absolute uncertainties at mC are beyond all but very qualified calibration labs.I also know that measuring temperature differences in time and space CAN be very accurate, if conditions are optimal. I frequently measured in stirred water baths that had a stability of around 0.005Crms overnight (checked with PT100 reference probes, and actually measured with 0.001 resolution, but with nothing near the same temperature uncertainty) with thermocouples. The reference points where huge water-ice slurry Dewars, the thermocouple measurements where done with Keithley Nanovolt meters and the PT100 where measured with a reference bridge). I am not an electrical engineer, but come from mechanics and thermal engineering. My PID / control loop maths are now a bit rusty but I have developed amplifiers for highly capacitive loads before. By searching new methods and ways, I have also more than once developed practically usable measurement techniques that people in advance told me where almost impossible ;-) The circuit I am working with, ONLY shows temperature of a sensor, heated by resistors, taped together, under a shield. I am aware that this is a serious limitation. Adding any mass to the circuit thermal feedback loop will be seen as an increased capacitive load to the circuit, so it will of course be harder to stabilize. Air convection, in and around the final solution is unpredictable and can dramatically change the heat transfer and temperature. I am mainly thinking of a heater that can keep a small circuit at a decently stable temperature, by which I mean in the order of 0.1C-0.01C. I am not really aiming for mC stability in a real life application, it was something I got, a bit to my surprise, for this circuit which is still on a breadboard level. But I think that a first board / circuit stable to the mC level is a decent start and I do think that kind of stability is possible in a very small scale. I think I will not be posting more on this until I have a complete working solution which may take a month or four... _______________________________________________ volt-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts and follow the instructions there.
