Hello to all, well i had a nice expirance of submitting the post, on the help of lcd interfacing.... well now i the problem is little bit different...
My problem is that i want to measure the Current (instead of Voltage) using ADC but the problem is that my ADC (or even all the ADCs) are capable of measuring the voltage (0-5v) but i want to measure the current ... so any one have idea how to measure the current...
Well i am working on project in which the current will be displayed on the Computer (in every instance of time) i might be using MAX232 with additional ADC with my 8051 MCU...(using UART) but the main problem is that how do i measure the current :-(
If the measurement circuit doesn't contain a known resistance, you will have to insert an extra resistor of known value into the circuit. The extra resistor will of course have to have a low resistance compared to the normal load, to not adversely affect the current.
The maximum quality of your measurements will greatly depend on how large percentage of voltage drop the extra resistor vill introduce.
If measuring AC current, the current is often measured using magnetic fields instead by the use of a transformer, where the load current is sent through one winding of the transformer, and the resulting voltage is measured on another winding. The problem with transformers is that they have a limited frequency response, so they don't work for DC or for very high frequencies.
"If measuring AC current, the current is often measured using magnetic fields instead by the use of a transformer"
There are also devices available using Hall-effect, and other techniques.
These have already been explained to you in your original thread on 8052.com: " href= "http://www.8052.com/forum/read.phtml?id=133674">www.8052.com/.../read.phtml
Again, you are wasting people's time as they are just repeating stuff that has already been given to you!
"There are also devices available using Hall-effect, and other techniques"
Since the goal seems to be measurement or integration of AC Power, there is a very elegant approach using analog Hall effect devices: measure the magnetic field with the Hall effect device whilst driving the Hall plates with an AC voltage sampled off the AC line.
That turns the Hall effect device into an analog multiplier, and in effect yields k*ei, or the AC power product.
I have designed a Hall probe that does exactly that, and the results are very accurate.