Reg doubt on ADS1230 gain

Hi Aravind,

After looking through the supplied document, I see a number of issues and contradictions.  Based on the code snippet the data is collected and converted from a binary 2's complement to an offset binary format.  This data is returned as 32-bit value from the function with 20 bits read from the ADS1230.  In the tables, the data is shown with values of 16-bit.  I've determined this based on the comments in the document stating that the value is neglecting the 4 LSBs.  The table also supports this as 0 volt input would be around 32768 (2^15 which is 1/2 of full-scale).  This is true for both sample 1 and sample 2 tables.  In each case the difference is about 1734 codes for each step, but below table 2 the average value shown is 10 times greater.

As to the calculation, the 16-bit data is being compared to 20-bit data.  The resolution voltage should be set to 16-bit, which is about 590nV per LSB.  This results in a code value near 1700 codes per 1mV.

For the gain calculation, this is also incorrect.  You need to either use 16-bit values for both or 20-bit values for both calculations and should not be mixing the them.  Also, if the actual reference voltage is lower, you cannot then use the theoretical to determine gain.  Another consideration is that in the calculation you are assuming there is no offset.

Best regards,

Bob B