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Millivolt Power Source?

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bobair8(at)msn.com
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Posted: Sat Jun 21, 2008 11:36 am Post subject: Millivolt Power Source?

<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Is there a reasonably easy way to fabricate a millivolt source to calibrate  an engine gauge?  I need something in the range of 10 - 100 mVDC, say  in increments of 10 mV.  I've got a bunch of resistors.  Can is just  start linking them together and checking with my voltmeter until I get what I  need?  

  

 I presume that once I get the right voltage, I won't have to worry about  blowing the instrument -- that it won't draw any more current than it is capable  of handling.  Correct?

  

 Thanks.

  

 Bob

   [quote][b]

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jetboy

Joined: 22 Jul 2006
Posts: 233

Posted: Sat Jun 21, 2008 2:09 pm Post subject: Re: Millivolt Power Source?

Instrumentation people use a purpose made calibration source for this,  what you suggest should be adequate for your task.



May I suggest obtaining a 10-turn trimmer in the order of 100 ohms and feeding that from 12v via a resistor around 5K ohms. that will give you as fine an adjustment you will need with the digital voltmeter across the output (middle connection of the trimmer) No need to limit the output as the 5K resistor will do that. If you have other than a 100 or 200 ohm adjustable pot, just fit a 100 ohm resistor across it.

Ralph

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Ralph - CH701 / 2200a

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Sun Jun 22, 2008 1:53 pm Post subject: Re: Millivolt Power Source?

Guys...



See: http://www.5bears.com/circuits.htm#Circuit%2001



One op amp and a couple resistors is the right way to do the job. Anything less leaves you at the mercy of....well I shouldn't tell you...you might be scared.

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