Sort of to do with EFI (more electronics)

[Jeffrey Engel]

Sorry, I didn't write what I meant to communicate.  By invert I meant 
that you can take a signal goes from 0 - 5 v and make it go from 
5 - 0 v instead.  That shouldn't require the negative power supply.

> From:          Orin Eman <orin at wolfenet.com>
> Subject:       Re: Sort of to do with EFI (more electronics)
> To:            diy_efi at coulomb.eng.ohio-state.edu
> Date:          Fri, 24 Oct 1997 18:45:16 -0700 (PDT)
> Reply-to:      diy_efi at coulomb.eng.ohio-state.edu

> 
> > << Op-amps.  You can scale and invert, even deal with shifted grounds 
> >  and stuff like that. >>
> 
> 
> > But you need to get -12/+12 volts for the inversion, a bit tricky on +12 volt
> > only system.  (Learded this the hard way).
> 
> True if you really want a -ve output... but often you want to use
> an inverting configuration to sum some inputs.  In this case, you can
> reference the signals to some other voltage, say half the supply voltage.
> Follow with a second 'inverting' stage referenced to the same voltage
> and it all works out nicely.
> 
> Remember that when you do use split supplies, there is no direct
> connection of ground to the op-amp, it doesn't know or care...
> It sees +/- 6V supplies with its non-inverting input connected to
> ground the same as a 12V supply with its non-inverting input
> connected to 6V as long as the 6V point is of low impedance relative
> to the input impedance of the op-amp.
> 
> BTW, the O2 sensor on my car is only sampled 100 times per second
> and 10Hz for the period of the rich/lean swings sounds correct...
> an op-amp is more than capable of following this.
> 
> Orin.
> 
> 
je
jengel at fastlane.net

     "I can resist anything but temptation"
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