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AD7705 data channels problem

Question asked by andrei799 on Jan 24, 2012
Latest reply on Jan 26, 2012 by andrei799

Hello,

 

I'm using AD7705 to measure 2 voltage levels. Circuit settings are: update rate 500 Hz, unipolar operation, gain 1, external clock oscillator 2.4576 MHz, SPI interface runs at 2 MHz, self-calibration was performed for each channel.

 

My problem is that when I read data from the first channel I receive data from the second channel and reverse (read channel 2 and receive data from channel 1) but if I read channel X (does not matter if it is channel 1 or 2) the first data is from the other channel and then if I read again channel X I receive the appropriate data. Which could be the reason for this?

As a backup solution I can do 2 consecutive readings and only the last data is correct but this take a lot of time, 2.2ms instead of 254us.

 

 

Voltage input for channel 1 is 6mV and for channel 2 is 2.16V

I attached a plot in that channel 1 is read but received data are from channel 2.

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