current measurement on LCD

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

  1. vectravanman

    Thread Starter New Member

    Mar 2, 2012
    12
    0
    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

    Expert

    Sep 9, 2010
    12,101
    3,033
    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
    5,939
    1,222
    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
    4,769
    969
    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)
     
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