[sdiy] Trying to establish confidence in my test equipment

[Harry Bissell Jr]

Or just use a 1.2V battery... its only off by 20% right :^P
  
  Suppose you have a crapy meter....
  
  You can't measure resistance with any precision... BUT even a cheap
  meter will usually repeat a measurement with very good repeatability.
  
  So you could match resistors pretty well with a crap meter. You would not
  know if they were 1K, or 1.2K, or .90K...   but you could say with some
  "confidence" (is it ?) that they were equal in value.
  
  Or get just TWO precision resistors, build a Wheatstone bridge, and use  your crappy meter to find the null voltage.  It may be .2V or  .02V... but you can usually
  have "confidence" that the meter is monotonic at least.  You can match
  resistors to very good precision.
  
  Or go to Mouser.com and BUY the 0.1% resistors... they are about $1.00
  each.  I'd buy the bag of 200 1% parts and match them using the crude
  methods I've described.
  
  Now the voltage reference is the ONE part you cannot easily verify with cheap
  equipment... but as was pointed out in the "oven controlled reference" post
  yesterday... a $5 surplus part might give you all you need and a $20 calibration
  with a known accurate meter would finish the job.
  
  I made these little calibration aids for myself so that I can quickly verify
  VCO operation. If you do that very often, maybe you can afford the very
  expensive meter.
  
  I prefer to spend the money on synths...
  
  Samppa wrote:
  Let's try this other way: Make a precision voltage reference. Then
take Your good old bag of 5% tolerance resistors, match a batch (I say
stick 'em to styrofloam, let them reach the room temperature ect.)
with Your badly or non-calibrated meter and build a resistive divider
from Your precision voltage reference down to GND.

Then look at the results with the "Pro precision gear" - How badly
voltages were off?
  If  you were "MOTM" this would never work.  If you were "EFM" it is  precisely how you would do it.  Suppose that PAiA required this kind of
    test equipment, would they remain in business ???
      
    Sometimes cheap and dirty really HAS merit. Its not the ideal way to go, but
  with careful planning you can do far better than the accuracy of your equipment seems to allow.
  
  H^) harry
  
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