Can I use the thermocouple simulator for MCP9600?
No, the thermocouple simulator has a source impedance that loads the MCP9600 inputs. The thermocouple transfer function polynomial is hardcoded and absolute. If the front end ADC is outputting binary that corresponds to thermocouple voltage at 1600°C, then the hardcoded equation will convert the voltage to °C with the precision shown in the device datasheet.
The simulator source impedance is not the same as the actual thermocouple impedance. The MCP9600 is production calibrated to meet the +/-0.5°C accuracy when connected to a thermocouple. Please refer to the specification stated in the device datasheet. Please not that there is no accuracy specification for thermocouple simulators.