I am try to get a thermocouple by AD7124-4 application again.

Hello

I met AD7124 IC two years ago.

I knew great works well. I made 10 boards on same circuit as bellow.

when I turn on the board and check a coldjunction temperature(RT1), the 5 borads temperature is different.

the 5 boards are about 24 degree and the other boards are 30 degree. the part is used same.

what do i do wrong? 

my code is like this:

1) reset data send ( 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff)

2) channel-0 setting ( 0x09, 0x10, 0xA6)      // AINP=AIN5,     AINM= AIN6

3) config-0 setting ( 0x19, 0x01, 0xEF)      // unipolar, ref_bufp

4) filter-0 setting ( 0x21, 0xE6, 0x07, 0xFF)

5) IOUT setting (0x03, 0x00, 0x12, 0x0B)

6) when i read, (0x01, 0x01, 0x84); // ADC controll setting

                         (0x42, 0x00, 0x00, 0x00, 0x00) // read

 i send number 6) messages on period.

please, check my setting codes and help me.

thanks for reading.