On Wed, Aug 5, 2009 at 12:56 PM, Pang<mailtopang@yahoo.com> wrote:
> Sorry, still in digest mode. So the reply is somewhat in digest mode too...hehe
>
> Hi Peter, Yea, did that.
>
> Hi Mike, they are all within the supply voltage. But the 4-20mA are
> independently powered.
>
> Hi XiaoFan, attaching the schematic.
>

If you really want to use differential mode, then you'd better use
a differential amplifier, something like AD629 which can withstand
high common mode voltage

As Mike mentioned, you have to be careful of the maximum common mode
voltage, which is often 1.5V below Vdd with the internal buffer is on.

-- 
Xiaofan http://mcuee.blogspot.com
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist