current measurement on LCD

Discussion in 'The Projects Forum' started by vectravanman, Mar 14, 2012.

  1. vectravanman

    Thread Starter Member

    Mar 2, 2012
    Hello all

    I have been tasked with measuring high side current measurement through an ADC. The ADC i am using will be incorporated in a PIC18F25K22 chip. Does anyone have any ideas on how i can manage this? I have managed to measure voltage using the ADC, is there a way use this output to get a current?

    The circuit is a 9V PP3 to the PIC, with voltage and current measurement going to the ADC of the PIC and the output of the PIC going to a 20x4 characted LCD Display
    Last edited: Mar 14, 2012
  2. wayneh


    Sep 9, 2010
    A picture (schematic) would be worth a thousand words here. But I'll ask the stupid question: Is there a reason not to just use a $5 multimeter set to its ammeter setting? Mine is good to 200mA and I suspect that would be enough for your device.
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    His teacher perhaps ;)
    But back to the topic. Current measuremnts are most often done using a small resistor on series with the load. Then measuring the voltage drop over this resistor. I think also Maxim have series of hi-side current sensors. If you use opamps. Check common mode range and max input voltage in respect to the supply voltage
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    Use a current shunt (basically a precision resistor) in series or even a hall effect sensor (provides additional electrical isolation if required) to measure the current. Many hall effect sensors have built in scaling to output directly to a ADC/micro. (commonly 0-5V scale)