Each of the eight channels has a diagnostic multiplexer in front. So, it can be enabled in order to monitor an internal node instead of the analog input signal (Vx+ - Vx-).
This can be enabled, when in software mode and +/-10V selected, by accessing the corresponding register (Address 0x28 to Address 0x2B) and selecting the temperature sensor.
Once selected, subsequent conversion will report back as ADC result the measure from the temperature sensor.
For example, if only address 0x2B above is overwritten with the value 0x03, the next conversion trigger will report back the temperature in volts, and needs to be translated into voltage (with the +10V range transfer function) and then to degreesC with the formula below:
Note the most accurate channel for diagnostics is channel 8, but none of them are a precision channel. Diagnostics mux is only for monitoring.
Note the transfer function above is for 18-bit AD7606C-18 generic. For AD7606C-16, replace 131072 by 32768