Olin Lathrop wrote:

>> 12V -----+----------+-----------+
>>          |          |           |
>>          R3         R5          R1
>>          |          |           |
>>          +-Vref+    +-Vref-     +-ADCin
>>          |          |           |
>>          R4         R6          R2
>>          |          |           |
>> Gnd -----+----------+-----------+
>=20
> I don't see any reason Vref- shouldn't just be tied to ground.  All sig=
nals
> are ground-referenced.  This also leaves a larger range for Vref+ and i=
s
> less complex.

The effective ADC resolution is a bit higher. Not much in this case thoug=
h
(around 10% increase). I don't see how this would affect Vref+ at all, an=
d
the increase in complexity is only two resistors.

With the values given (R1=3D1270 =D9..13632 =D9), R2 could be something l=
ike 500
=D9. That gives for ADCin a range of roughly 0.6 V..4.5 V @ 16V (assumed
highest voltage) or 0.4 V..3.4V @ 12V. There's not much of a point in bei=
ng
able to measure voltages below the lower limit, so Vref- could be set to
that voltage (or of course a bit below), with a small gain in resolution =
--
which probably is not really relevant in this case. But I don't see how i=
t
could hurt.

Gerhard

--=20
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