I have installed a number of these compasses on identical boards, and I've found that not only do their measurements differ, but also even the range of values.
at the same position and direction, they give significantly different values for +/-. This is a slight annoyance having over 50 boards to go in the firmware and adjust the offsets before calculating the direction, but is this a common thing?
Lastly and more worrying is the difference in ranges that the values give when i read from them in all 360 degrees with maybe 16 increments. For example, one compass may give a maximum value for + of say 2 volts and a minimum of 1 volt, with the same for the -. Another may give a range for + of 1.5 volts to 1.7 volts, and the - may give 1 volt to 2 volts. And another will have .8 volts to 2.5 volts for + and 1.1 to 1.15 volts for -. Are these common issues? they are all implemented on identical boards.