Electronics > Metrology

TL431

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GigaJoe:
to be precise AZ431AZ-ATRE1 , Diodes Inc.

3 in parallel , current source on the same 431,  with 50ppm resistors , 10mA  for all 3 ; OP77 as averaging.
it in cardboard box, somewhere tossed far away ....  and occasional measurement

seems after 1 year result kinda acceptable,


result:

Month   Day  Voltage (Temp in C , approx)

++++++++++++++++YEAR 2022:
05 20 START UP

07 05 2.49237
07 06 2.49219
07 07 2.49207
07 11 2.49188
07 13 2.49173
07 15 2.49160
07 16 2.49155
07 17 2.49168 (21)
07 23 2.49171 (20)
07 26 2.49166 (22)

09 06 2.49345
09 27 2.50434

++++++++++++++++ YEAR 2023:
08 15 2.49612 (23)
08 18 2.49610
08 24 2.49611
08 27 2.49611
08 29 2.49609
09 04 2.49610
09 08 2.49613 (23)
09 20 2.49620 (19)

(last result , colder dry weather , vs hot raining days )

armandine2:
I was playing with a TL431C last weekend --- beginner's stuff from H&H 3rd edition, the overvoltage crowbar with a triac

... did the rough Vref calculation using the values of the potential divider resistors and the Vin at the overvoltage point.

Came out as ~2.5V

which was surprising to me as I saw in H&H 2nd edition a Vref value of 2.75V  :palm:

EC8010:
Typo. We all know that TL431 reference voltage is 2.5V. And I'm sure H&H do, too. You'd be amazed how easily typos creep in. TL431 is quite a useful part.

armandine2:
they were consistent with this one

EC8010:
Consistent error noted. I briefly wondered if TL431 reference voltage had changed through lifetime, but I've replaced a TL431 on an ancient piece of kit (late 80s) with a new one without needing major changes. Looks like an author error rather than typesetting. Easily done. I remember stating "Two squared is nine" at the whiteboard of my first lecture and it was only on the third instance of saying so realised what was causing the error in my calculations. Moral: At the whiteboard, simple arithmetic encounters quantum uncertainty, and students will swallow anything if it's spoken with enough conviction.

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