The offset self-calibration command corrects internal ADC1 offset error. Program the ADC1 input multiplexer register (INPMUX) to FFh to force open all input connections before sending the command. When the SFOCAL1 self-calibration command is sent, the ADC shorts together the internal PGA inputs, then averages 16 readings to reduce the conversion noise for an accurate calibration. When calibration is complete, the calibration result is written to the 24-bit offset calibration register (OFCAL[2:0]). After calibration, set the input multiplexer to the desired measurement channel. The offset calibration register is disabled in chop mode.