The Honeywell 394530 Thermocouple Tester is a compact, reliable tool designed for testing thermocouples quickly and efficiently. It helps diagnose issues in thermocouples by measuring the millivolt output to ensure proper functioning. This tester is ideal for HVAC technicians working with gas furnaces, water heaters, or other appliances using thermocouples. https://www.partshnc.com/394530-resideo-thermocouple-tester