Sort of to do with EFI (more electronics)

[Clare Snyder]

dzorde wrote:
> 
> My understanding is that the sensor (in most cases) is just used to make up
> a voltage divider, scale the other resistor correctly and you could
> technically connect directly to the ADC.  Although I'd suggest a bit of
> filtering and probably an op-amp before the ADC.
> 
> Dan     dzorde at geocities.com
> 
> >Hi,
> >The following email is about A-D conversion of inputs from various
> >sensors. It's not really about EFI (sorry) but as some of
> >you may know the answer, I post it here :o)
> >
> >I am in the process of making a digital data-logger which uses an 8051
> >(similar) with 6 channel A-D conversion on chip. All seems to be ok. I
> >have the LCD, a PIC 16C55 controller board interfacing to RS232 that all
> >works ok. Now, the quest is to interface it to the real world. In
> >researching this, I have decided to use 80C550 or 87C748. There is no
> >reqirement in the design to use a serial link, so they should be ok.
> >The questions I have are;
> >    The oil temperature, water temperature, oil pressure sensors use
> >what range of voltage? It is my understanding that they ground a "12V"
> >signal and the resulting current flow is used as the measure of sensor
> >range. Is this true for all the sensors?
> >If you know about A-D conversion, I am stuck at this point not being
> >able to interface the 8051 family A-D converter to the real world. ( I
> >am a computer engineer, I know a little about digital electronics, but
> >obviously lack quite a bit in this area )
> >    I found a great site www.8052.com that gives many details about the
> >chip, interfacing and programming. At the moment, everything to do with
> >the 8051 seems to be sorted out except for the Analogue part!
> >
> >I would appreciate any help or suggestions, if you are interested in the
> >project, it is no top secret, so I would be pleased to share more
> >details with you.
> >
> >Thanks in advance
> >Tim Freeburn
> >
> >
> >
> >
In FI applications the voltage devider is complete in the sensor, but
oil pressure, engine temp, etc sensors for standard automotive
instrumentation are not that sophisticated. They are simple variable
resistors - and will make a non-linear voltage devider when coupled to a
fixed resistor. Some oil pressure sensors give a pulse instead of a
resistance - so beware - some will not work at all as voltage deviders.
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