Fieldpiece ATH4 Dual-Temperature Accessory Head Designed for HVAC/R, the Dual-Temperature Accessory, model ATH4, measures two temperatures and calculates the difference in English or metric units Field calibration for 1-Degree F accuracy Displays -Degree F directly at 01-Degree F resolution on DMM with 01mVDC resolution Select Degree F or Degree C Converts from -50-Degree F to 1800-Degree F (optional thermocouple required for 1800-Degree F)