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Author Topic: Arduino Due Analog Pin Impedance  (Read 462 times)
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Ohio
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Does anyone know what the impedance is on the analog pins on the Arduino Due?

I've got a sensor that's resistance ranges from 25 to 375kohms and need to know this to see if its going to work or not.

Thanks.
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nr Bundaberg, Australia
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AFAIK it varies with the speed you run the ADC, table 46-35 shows the "Source impedance values" and they range from

10k with ADC clock of 20MHz
to
274k with ADC clock of 1MHz

It takes 20 clock cycles to take a reading so you can do the maths as to the sample rate. As for what rate is set by the Arduino init code I have no idea but I would assume they went for the fastest.

In other words the faster you want to sample the lower the source Z has to be.

This is for 12 bits, for 10 bits the Z can be slightly higher, ie 14k and 353k for the above speeds.

______
Rob
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Rob Gray aka the GRAYnomad www.robgray.com

Ohio
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Got it.  I understand.

I read the table you are speaking of a wasn't sure if that was what I was looking for or not before posting.
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