[volt-nuts] Best reference after LTZ1000

Marvin E. Gozum marvin.gozum at jefferson.edu
Sun Aug 15 19:34:29 UTC 2010

What do you think of Geller's work?  He uses the AD587 as a voltage 
reference, and writes of results > = the AD specs.

Your need seems close to the principle used in his thermal 
anemometer,  which he patented.  IIRC, it measures temperature change 
as changes in the stable voltage response of a reference, which is 
then proportionate to air current.


 From the link, and use his patent number to describe the process better.

PS: This is my first post.  Thank you all for the good information.

At 06:03 PM 8/14/2010, Andrea Baldoni wrote:
>On Sun, Aug 15, 2010 at 08:47:03AM +1200, Bruce Griffiths wrote:
> > The internal current source is derived from the internal reference via a
> > few opamps and resistors plus some JFETS etc.
> > To a first approximation its value only depends on the value of a
> > resistor and some resistor ratios.
> > Thus the current tends to track drift in the internal reference.
>Maybe I start to understand.
>I may use the 4W ohm measurement, derive a Vref from the force connection
>using a stable resistor, for instance 1V from 1K; use a good 
>operational+MOS to
>make a current source from this Vref, say 10uA using 100K; measure 
>the drop over
>the RTD with the sense connection and voila', the reading directly 
>in ohm x100.
>This way, no need for an external source at all and also the meter could read
>at full speed because it has not to multiplex between the two inputs like in
>ratio VDC:VDC.
>Very nice!
>As soon as I receive the OP177s I'll try it. I have just to pay attention to
>track the heating of the 1K resistor with the 100K, because 1mW is not to
>The same could be done in reverse, to make a microohmeter out of the 34401A.
>Best regards,
>Andrea Baldoni


Marv Gozum
Philadelphia, PA 

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