[Diy_efi] Question relating to old posts.....cheap

[Mr Motor]

ok, bare with me here.....i'm no electrical guru. I now
understand how the IAT functions. I get THAT PART.

Now, all this resistor stuff is where i dont know what you are
talking about. Are you telling me that i can wire up the IAT
sensor with some resistors to give it a constant 5v power supply
and then it will work with the dataq 194?

Thank you for your patience

jim




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---- On Sat, 7 Jun 2003, Perry Harrington (pedward at apsoft.com)
wrote:

> IAT sensors are thermistors.  Their resistance is a negative
logarithic function.
> At low temps they are high resistance, at high temps they are
low resistance.
> 
> To sample an IAT you need a bias resistor to provide a pullup
to +5v,  ECUs have
> these internally. If you want to use an IAT by itself, you'll
need to wire it up
> with a bias resistor.
> 
> Basically, you'll need a regulated 5v power supply, an LM7805
is sufficient.  You'll
> need an appropriate bias resistor.
> 
> There are only 3 *major* values of thermistor out there.  GM,
Ford, and Bosch/Nippon
> Denso.  For GM, use a 2.49k bias resistor, for Ford, use a 27k
bias resistor, and for
> Bosch/Nippon Denso, use a 2.2k resistor.  At 81 degrees
fahrenheit the thermistor's
> resistance will equal the bias resistor's value.  You can use
a voltage vs temp curve
> for a GM sensor if you use the above bias values.
> 
> The sensor is tied between ground and the bias resistor, you
read the output from this.
> The bias resistor's other leg is tied to +5v.
> 
> That's the short and sweet of how you read an IAT sensor
without an ECU.
> 
> --Perry
> 
> On Sat, Jun 07, 2003 at 07:35:01PM -0500, Tim Drinkwater
wrote:
> > I wouldn't be the one to ask I'm more or less just a lurker.
 I only 
> > more or less know the general principles of EFI.  Hopefully
someone else 
> > can help you out.
> > 
> > Tim Drinkwater
> > Mr Motor wrote:
> > > Yup, that is what i was looking for thanks. :)
> > > 
> > > one thing i'm not sure about is if this is going to work
for
> > > what i want it to do. Do you know how IAT sensors actually
work?
> > > electrically? 
> > > 
> > > it says in this link that "Examples of low level signals
that
> > > are not suitable are directly connected thermocouples,
> > > thermistors, RTDs, strain gages or strain gage-based
> > > transducers." 
> > > 
> > > Do you know if i can datalog IAT temps using this
software
> > > setup? Thanks
> 
> -- 
> Perry Harrington			Data Acquisition & Instrumentation, Inc	
> perry at dainst dot com					 http://www.dainst.com/
> 
> Those who would give up essential liberty to purchase a little
temporary safety
> deserve neither liberty or safety. Nor, are they likely to end
up with either.
>                              -- Benjamin Franklin
> 
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> 
> 


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