Heat Spy Temperature Sensor Gun is a low-cost electronic device used for verifying and monitoring dryer temperature. Use it to locate and control heat build up in the substrate, potential electronic system failures or possible over heating. Excellent for use in critical heat sensitive applications, such as textile and UV curing, or anywhere where maintaining temperature is important. Powered by a universal 9 volt battery an measures from 0 to780 f (or 18 to 400 C)