Electronics > Metrology

LT1021 plastic

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im going cheap, as usual ... :)

a while ago i did 16 plastic LT1021, paralleling together over some balancing resistors, with adjustment  and inside a thermostat.
As the thermostat itself are good, all this construction became a bit better than disaster, an output swing at non predicted level, randomly going up and down.

Im goin to the next loop of cheap :)

so i pick random used LT1021-10 PDIP8 ,  add basic china multiturn resistor, 1N4148 as compensation, from +20C to +40C , i got negative swing of 4 microvolts. basically lucky. tossed in plastic container,  add 2 5W resistors, container filled by oil ,  everything in a thermos.   basic 12V regulator

it run it some period on March, (let say 500 hours) ; and on april I sporadically did a measurement , just to see a tendency ..  ; measurement device 34401a , with positive tempco, and room temp usually +18, and was +20  during mid April heatwave.

im guesin - 4 (or 6) such modules ,  adjusted to min tempco ,  a bit running a couple month ,then adjusted to the same output , (avoiding balancing resistors) probably make sense. 

attached file of sporadic measurement, and guessing Temp inside of oil bottle as thermistor not calibrated. 34401a I think +0.8PPM

Interesting.. Mind the measurement with 34401A is tricky, from my experience.. It needs 8-12h to fully stabilize and its TC depends on elapsed time after the power-on. A measurement here takes a day..
I collected around 40pcs of epoxy 1021-10 and -5, their TC -1 to +4ppm (simple finger method). The idea with the oil is interesting. Perhaps I would dry the epoxy first and then put the package(s) into the oil, the oil should not be hygroscopic.
Why do your temperature in the thermos flask vary so much (3C)?

multimeter are constantly on , 2 years maybe ... switching display off . had some fun with insulate LM , add some shields, maximum possible filter caps, add some poly on top of tantalum. switch back\frond - soldered ;  kinda modding does it helps no idea.

the temperature not stabilized,  just 2 resistors ,  so it depend on ext. temp. and i think i stacked something on top , so temp dissipation does lower and temp, increased.
the lowest air room temp around +17 highest maybe 20-21 , in a month period.  I'm really have no idea why i add non stabilized heater,  guess it was assumption it smooth deviation, it probably can ,  but need carefully build a carrying case so excess power dissipation need more less constant.

im quite satisfied , had assumption it would much worse. LT1021 I actually pick with really high tempco like 20ppm ,  so ruthlessly fire it up , but it works,  I add 5 diodes to compensate tempco .  I have an idea to add diodes till temco change sign,  then add something ( potentiometer , something else)  to the last diode for adjusting the level how this diode will affect tempco.

20230502 9.999843
20230806 9.999750

Yep, I still wonder how it is possible people so often report "great" results from their cheapo 1021 based calibrators..
Afaik Andreas and dietert1 reported good results when keeping the 1021 at elevated temperatures - like 50C and 42C, and 24x7 powered on.


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