Magnetic Surface Thermometer (NIST/ISO Certification Optional)PTC 315C Magnetic Surface Thermometer 15 to 65C The top bimetal surface thermometer on the market for over sixty years. PTCs surface thermometers are unrivaled for their combination of accuracy, quality, versatility, and economy. Manufactured from the finest materials, these instruments will continue to give accurate readings for many years. Features: Accuracy + 2% Every unit individually calibrated Time constant from 0. 06 to 1 minute Division 1