I am needing to build a unit that switches off an element between 300 to 400 degrees. The LM35 has a max of 150°. Is there another sensor available

 

You cannot use a semiconductor chip at those temperatures. You will likely need a thermocouple.

 

Hello,

You could also measure the temperature using a PT100:
http://www.ni.com/white-paper/3643/en

Bertus

 

I had no I idea RTDs had such a range.