read 1 sensor with 2 PICs?

[Acetronics2]

Hi, Picn' ...

QUOTE [ and I'm using a 100 Ohm resistor between the input pin and Vcc on each PIC. ]

Wonder if there is really ONE resistor for EACH Pic ...

Logically, there must be only ONE resistor in series with your probe ... so, the second PIC input must NOT have a 100 Ohms resistor from +5v ...

I'm not sure ... but that can be a very good reason for misrunning ...

Alain

[PICn_n_grinnin]

Hello Alain,
Thanks for your reply. I think we tried the setup with only one resistor, but now I can't remember for sure... I'll be going to the lab later today and will try that. Do you think there should not be a problem with having the two PIC's A/D pins tied together?

[Acetronics2]

Hi,

For the supply, if the two PICS have a COMMON GROUND and BOTH a very close to 5 v supply ( do not forget PIC protection diodes on the inputs ...), I don't see any problem ... as your sensor impedance is low enough.

For common Ground ... keep in mind there should be only 1 common ground connection point to avoid "ground loops" ...

Alain

a scheme of each of your ADCs inputs could help greatly too ...

[PICn_n_grinnin]

Alain,
The two PICs are on seperate circuit boards, each with its own 5V. switching regulator, and there is a common ground between the boards. I'm a little unclear as to what you mean by the protection diodes. What type of diode and where should they be placed?
Thanks,
Pete

[Acetronics2]

These are INTERNAL Pic protection diodes ... If supply voltage of the 2 Pics were differents, that could create problems, so we must not forget them in such situations !!!

One more point, is your sensor connected to ground on one of its sides ???

Alain

[PICn_n_grinnin]

Alain,
OK, my face is sufficiently red! I forgot to take my smart pill this morning. As I mentioned, I will try the single resistor and will let you know the results.
Pete