Current monitor panel

Can any one please guide me i want to design a current monitor numeric LCD display with the help of C.T 20/5A , 89c51 micro controller, and ADC 0804 now problem is i have 20 A load and want calculate shunt resistor to convert it into voltages level..

kindly guide me how i can..

Perhaps better to use a hall effect current sensor:

* http://scienceshareware.com/how-to-measure-AC-DC-current-with-a-hall-effect-clamp-.htm
* http://www.nktechnologies.com/current-sensing.html
* http://www.digikey.com/product-detail/en/HTB 50-TP/398-1075-ND/1701118
* http://www.automationdirect.com/adc/Overview/...C)/Current_Transducers/DC_Current_Transducers

I've never used one, but they look like a "better" solution than using a shunt resistor (actually, do you mean a "current sense resistor" or are you talking about a shunt for a current meter?) Either way, using a hall-effect sensor does not impinge on the circuit the way an in-circuit approach does (e.g. series resistance or series ammeter).

Try Googling for subsets of your design:
* Search for LCD display circuits
* Search for ADC 0804 circuits
* Search for applicable 89c51/ADC 0804 application notes.