I have been playing with the Digilent DMM shield and trying to understand how the shield and the ic hy3131 work. My question is about the multiplication factors which are used for converting the adc value to real value.
For example, the multiplication factor in the library for 5V DC range is: 125e-1/1.8/8388608
If I'm correct, in 5V DC range the input signal is divided by 10 and fed into the adc whose reference voltage is 1.2V, so my question is why we multiply the value by 12.5? Shouldn't it be 12.0 instead because the reference voltage is 1.2V?