How can i use ADC to measure Current?

[smuscat]

I need please ideas how to use DAC to measure current.Currently I have built DAC to measure voltage, the type i built is the STAIRSTEP RAMP the 8 bit one.

 

[mgb_phys]

An ADC measures an analogue voltage a DAC generates one.
Since it measures voltage you have to convert the current into a voltage.
The normal way to do this, eg in a digital multimeter - is to connect a small resistor in series and measure the voltage across the resistor, then use ohm's law to calculate the current. With AC it's a little more complicated - you will have to measure the voltage at many points in the AC cycle and calculate the RMS.


What sort of current / voltage are you looking at?
If you are doing this with very high currents (eg car battery) or high voltages (eg household wiring) you probably want to learn a little more before you try.

 

[Topher925]

is to connect a small resistor in series and measure the voltage across the resistor

These are known as current shunts and are used everywhere in industry. You can buy them for less than $50 from a lot of industrial suppliers and they usually come pre-calibrated. Most shunts available are 50/50 shunts which basically means 50 amps = 50 millivolts so all you have to do is just shift your decimal point.

http://www.rc-electronics-usa.com/current-shunt.html

 

[smuscat]

DC current i need to measure.I have a problem because it reads a resolution of 5V/256 0.02Volts the voltage is too large i think.Beause the voltage generated by the shunt is too small i think.

 

[mgb_phys]

For a real world application you will need an amplifier before the ADC.
In order to get a larger voltage, you would need a larger shunt resistance which will waste energy and reduce the voltage in the circuit.

For somethign like a simple science fair experiment or just to roughly monitor a voltage in a low current application you could use a large eg 1 Ohm resistor.

 

[smuscat]

Thanks an amplifier like a non inverting one fits well in my circuit.