The serial prints are separated because the multiplexer can read up to 8 channels, so loop through them. At the moment I just have one thermocouple connected, but once it is deployed I will be logging several using this one unit. I have to admit my understanding of the multiplexer code is very limited. The code is an example from ocean controls which can be found here... http://oceancontrols.com.au/KTA-259V3.html This code prints the temperature readings to a serial monitor. I am trying to adapt this code to write to the SD logger. I have tested moving around the point where I log the data, and tested this with additional serial prints which confirm the value is not 0.00 at those valid points.