Current measurement

[exodia505]

Hello!
what's the best way to measure current with pic ?
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NOway!!

[asmboy]

it all depends on:
1- AC?
2-DC?
3-the RANGE ?( 1 ua is very different from 100A )
4- and if AC - the FREQUENCY range

[exodia505]

i meant DC current (0-5A)
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NOway!!

[asmboy]

Hi side or low side sensing -or floating?

Whats the CIRCUIT you intend to use this with ??

Even with an optimum circuit,
keep in mind that with a 10 bit A/d pic
you can only resolve to 7.8 ma increments and 1.95 ma with a 12 bit PIC.

The circuit you will need depends on the answer you give to the first line of this message.

BTW: for real product - or school project??

[gpsmikey]

Contact or non-contact (can you insert a sense resistor in-line with the load or do you have to not modify the wiring) ? What kind of frequency response do you need ? (there is DC then there is "fluctuating DC" where you are monitoring a load for example). What kind of voltage drop can you tolerate across the sensor ? To "measure current" you first have to define the requirements of what sort of "intrusion" into the circuit you want to measure can be tolerated.

mikey
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mikey
-- you can't have too many gadgets or too much disk space !
old engineering saying: 1+1 = 3 for sufficiently large values of 1 or small values of 3

[SherpaDoug]

Look at these chips for high side current sensing:

http://datasheets.maxim-ic.com/en/ds/MAX4373-MAX4375.pdf
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The search for better is endless. Instead simply find very good and get the job done.

[Mike Walne]

Is your current unipolar?

You said 0-5A, but could the current change direction? (i.e. -5A - 0 - +5A)

Where abouts in your circuit are you wanting to measure? (0V lead, above VDD, below VSS, floating)

Do you need a Hall effect probe?

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And on and on .........

Mike