The AP1 Carbon Probe is a consumable item, like a thermocouple, which is mounted with its tip in contact with the furnace atmosphere, ideally close to the working zone. The probe produces an output voltage which, in conjunction with the process temperature and atmosphere, can be interpreted in terms of the atmosphere carbon potential of the furnace. The probe is designed to be used with controllers with a high impedance input. The Eurotherm AirRef enclosure provides a continuous reference air supply to support the standard operation of the probe.