[sdiy] Trying to establish confidence in my test equipment

[Harry Bissell Jr]

Right you are...  ;^P
  
  The National website suggests the LM4050 which has 50ppm
  max tempco.  (if you are that worried about it :^)
  
  OK its an SMT package so its harder to solder...
  
  The metal film resistors ~most~ of us are using in our designs are
  100ppm or 50ppm. Trimpots and caps are usually MUCH higher than
  this. 
  
  The tempcos are 3300ppm.  Residual drifts, from those list members
  who are measuring this for their VCOs... is probably in the 100-150ppm
  best case, with careful trimming by hand.
  
  So I'm suggesting that a 100ppm (or 50ppm) percision reference is really
  pretty good, compared to the levels of precision that everythign else has...
  
  Now without getting too silly...we could buy a simple thermometer and
  measure the temperature of the lab...  We might expect it to be 25C +/-
  a few degrees...  (except in Jim Patchell's lab where I hear its 50F, he needs
  the furnace fixed iirc).
  
  The measurements would NOT be precise over wide temperature ranges...
  but even a CHEAP thermometer would tell us that the temperature was
  reasonably the same (or that it is not).
  
  We would NOT know that the temperature was really 25C... it might be 22C
  or 28C... but again we expect that it would read the same on consecutive
  days.  Again, its a repeatability question, not an accuracy question.
  
  I'm not saying that its BAD to have expensive test equipment...
  just that their is no reason for a newbie to wait ten years until
  he can GET the good equipment.
  
  H^) harry

Samppa Tolvanen <samppa.tolvanen at gmail.com> wrote:  On 3/8/06, Chris Manders  wrote:
> Hi Harry and everyone
>
> Now they are useful! Many thanks for the pointer.
>
Hi Chris and especially H^) harry ;)

> 5.000V and 10.000V exact references.

Did You notice 100ppm/Celsius degree temperature cofficient? Now we
have the problem of scaling being off because reference voltages are
not in the same temperature as the circuit measured - Don't we?

Samppa


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