didgital nano and pico ampere meter

[lats]

nano ampere meter

dear friends
i want to design an digital ampere meter with following specification:

digital nano ammeter ( 1 - 999 nA)
pico Ammeter (1-999 pA),


i will be using lcd display and 89c51 microcontroller.
please any body help me out for how to design it.

byee
lats

 

[VVV]

pico ampere meter

I think you should use an analog front-end, followed by and A/D.
Take a look at appnote AN-242 from National.
You can probably adapt circuits of figures 11, 12, or 14. Use their output to drive the A/D.

www.national.com/an/AN/AN-242.pdf#page=6