Re: [ts-7000] Re: Bad distortions on MAX197 readings (via adc_logger)

[Jim Jackson <>]

On Sun, 24 Feb 2008, j.chitte wrote:
>> On my 7250 I have an R2R network DAC running of 4 bits of portA .
>> This is far more linear than I expected from such a simple circuit.
>> An on screen plot looks as straight as a die.
>>
>> However , I am monitoring it with one channel of the MAX ADC
>> and there is some very bad distortion of the values it returns.
.....
>
> Anyone have any idea what this gross distortion is about?
>
> If I run this on range 3 (0-5V) it bigger and uglier and right in the
> area where I need results.

If memory serves, the input impedance of the MAX197 is about 17K.
What resistors are you using for your R2R ladder? Do you have a buffer 
between the ladder and the max197 input?


 
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