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AD7190 problems

Question asked by anupmathew on Jun 1, 2013
Latest reply on Jun 5, 2013 by ChrisD.Rama

Hi,

     we have planed for using the AD7190 ADC  for weighing. while testing we have face some problems. we are choosing 100/200hz data rate,gain=8,sinc4 filter. we are using SPI of  PIC16F877A microcontroller.

We have done the following settings in our program

 

reset adc by sending 40 consecutive 1s

 

 

1. set configuration register values 0x000103  (hex-values) . 

             a)  For disabling chopper,

             b)  External reference applied between REFIN1(+) and REFIN1(−),

             c)  channel 1(ie between AIN1 and AIN2) 

             d)  disable buffer

             e)  Bipolar mode

              f)  gain 8

 

2.set mode register  value as 0x880430 (hex-values)

            a)  Internal zero-scale calibration.

            b)  Internal 4.92 MHz clock.

            c)  enables a notch at 60 Hz

            d)  sinc4 filter

            e)  FS=48 for 100HZ output data rate

 

3.set mode register  value as 0x080430 (hex-values)

 

            a)  continuous convertion

            b)  Internal 4.92 MHz clock.

            c)  enables a notch at 60 Hz

            d)  sinc4 filter

            e)  FS=48 for 100HZ output data rate

 

In this settings we get 16 bit stable value. but while changing the settings we face some problems

1.when we enable the buffer only zeros are get as output.

2.when the mode is change to unipolar only zeros as out put

3.when we enable the chopper the values are not stable

4.while enabling both chopper and buffer at the same time then also zeros are ouputs

 

The output values according to different settings are attached below. we use 5volt and 6volt power supply.And for data transfer we use SPI of PIC16F877A. And the reference voltage in the ciruit is 4.8volt.This is our program and schematic

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