ComputerVoltageSources

I think you're on the right track.  Use a voltage reference chip, not your
power supply.  Feed this to a high accuracy low voltage offset differential
amplifier with high gain.  Your + and - input resistors are the ones to be
matched.  If both are attached to the voltage reference then the output is
only the difference between the two and the op amp offsets.

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com


> -----Original Message-----
> From: ComputerVoltageSources@yahoogroups.com
> [mailto:ComputerVoltageSources@yahoogroups.com] On Behalf Of John Mahoney
> Sent: Friday, March 24, 2006 8:03 PM
> To: ComputerVoltageSources@yahoogroups.com
> Subject: [ComputerVoltageSources] resistor matching, was RE: Calibrated
> Inputs
> 
> Re: matching resistors, will the following procedure work?
> 
> Ingredients:
> 	1 precision voltage reference
> 	1 amplifier
> 	1 voltmeter
> 	Resistors to be matched (RTBM)
> 
> Feed a small, precisely regulated signal through a voltage divider
> made from an RTBM and some other resistor (the "constant"). Feed the
> divider's output through the amplifier. Measure the output. Repeat as
> needed.
> 
> The idea, obviously, is to amplify the differences between the RTBM
> so that the voltmeter can register those differences. Concerns would
> include temperature stability, power supply stability, etc...
> 
> So, this may not be good enough for a NASA guidance system, but will
> it suffice for this DIY project? As John Lofflink said, we need only
> be concerned with relative accuracy.
> --
> john
> 
> 
> 
> 
> Yahoo! Groups Links
> 
> 
> 
>