I have understood how auto-ranging is typically achieved on a digital multimeter, but I'm having trouble finding an example of how (DC) polarity is handled. How does the meter know if a voltage is negative (to show a '-') and not fail from having a negative voltage on the ADC?
I figured it could possibly be done by having ground be in the middle of the ADCs range? (eg by having values: 0 @-2v, 1024 @0v, 2048 @+2v)
So: How is polarity measured/detected in DMMs? (pros and cons of different methods would be useful)