J.C. Whitney AFR meter

[Randall]

Rex Weatherford wrote :
>
> I was looking at the schematic for Dave's meter and had a few
> questions.
>
> What is the LM3914?

It's an integrated circuit made by National Semiconductor, designed to
create a bar graph display with a minimum of external components.
National's data sheet is at http://www.national.com/pf/LM/LM3914.html .  The
part should be available from most full-line electronics supply houses
(which leaves out Radio Shaft).
>
> It says I can buy a meter like this from JC whitney for $20?  Is that
> true?

Not quite.  Current price is $36.  See
http://www.jcwhitney.com/product.jhtml?CATID=4571 .
>
> How are these used...  I know that my ECM looks for values
> between .100v
> and 1.1v.  And that my EGO sensor has to warm up before this means
> anything.  Correct?

Basically.  The LM3914 uses 1.2v as the reference (full scale), I assume the
Whitney meter does the same.  I believe the EGO sensor output is basically
meaningless above about 0.9v.

Randall

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