req:8051 based volet and ampage meter

From your questions it is obvious that you should park your project, and spend some time on genereral electronics.

You can not build a multimeter unless you either find a complete schematics + software + PCB or you aquire the knowledge about how they work.

You can't send any current into a processor pin. You use shunt resistors for that. Standard electronics knowledge tells how to compute resistances and required power specification - and how much the shunt resistor will heat up when measuring.

The data sheet for the processor specifies the voltage range for an ADC input, and if the processor has programmable gain and if it supports alternative voltage references.

I don't know what 1mf is. m = milli = 0,001. f = femto = 1E-15. Did you mean mF as in milli-farad? That is a capacitor and is only needed if filtering AC. Once more, computing low-pass filters requires electronics skills.

No normal ADC (any at all?) return any current or voltage as a float. They are linear or logarithmic and returns the measurement in a number of bits. You have to use basic programming skills to convert from the ADC value to the display value, taking into account the voltage reference, the full-range measurement value, any programmed gain, etc.

You use multiple processor pins if you want to measure multiple channels. But you don't use more pins to get a larger measurement range.

In short: Pick up a basic electronics handbook. Start studying. Only you can do the work needed for you to learn what to do, and why and how.

From your questions it is obvious that you should park your project, and spend some time on genereral electronics.

You can not build a multimeter unless you either find a complete schematics + software + PCB or you aquire the knowledge about how they work.

You can't send any current into a processor pin. You use shunt resistors for that. Standard electronics knowledge tells how to compute resistances and required power specification - and how much the shunt resistor will heat up when measuring.

The data sheet for the processor specifies the voltage range for an ADC input, and if the processor has programmable gain and if it supports alternative voltage references.

I don't know what 1mf is. m = milli = 0,001. f = femto = 1E-15. Did you mean mF as in milli-farad? That is a capacitor and is only needed if filtering AC. Once more, computing low-pass filters requires electronics skills.

No normal ADC (any at all?) return any current or voltage as a float. They are linear or logarithmic and returns the measurement in a number of bits. You have to use basic programming skills to convert from the ADC value to the display value, taking into account the voltage reference, the full-range measurement value, any programmed gain, etc.

You use multiple processor pins if you want to measure multiple channels. But you don't use more pins to get a larger measurement range.

In short: Pick up a basic electronics handbook. Start studying. Only you can do the work needed for you to learn what to do, and why and how.