> >2) add an
> > adjustable regulator to the main power supply and provide a new
> > regulated voltage to the input side of the thermistors to bring
them
> > into range or
>
> I'd need to know a little more about the thermistor you are using,
> some have a required voltage operating range. I would suspect this
as
> it was using a 7-8V input (I assume regulated, and thats a lot of
> trouble if 5V which was readily available was not used).
>
> Why not just a divide by 2 resistor divider?
>
> If you use an op-amp you really want to use it to generate a
> difference voltage from a fixed voltage. Which can be done with a
> resistor divider on the thermistor, and 2 resistors to set the gain
> from the reference voltage.
>
On the schematic for the 5V power supply there is a line voltage
output labelled ALG12. It is not a highly regulated output like the
+5V part of the supply. This voltage is used all over the board so I
don't think this was special for the thermistors. The 5V is regulated
using a LAS6330 and is only used to power the chips and provide high
state logic. Various other circuit are powered from this feed.
What would a divide by 2 divider network look like and what values
for the resistors ?