Probes

CHT Type J – Type J sensors are usually identified by yellow (-) and black (+) wires. A small number of manufacturers use red (-) and white (+) or red (-) and black (+), but yellow and black is considered the industry standard. Type J thermocouples are made of iron and constantan metals. Type J thermocouples are more accurate in lower heat range and are used primarily for CHT instruments.

CHT/EGT/TIT Type K – Type K thermocouples are identified by red (-) and yellow (+) wires. Type K thermocouples are made of alumel (red) and chromel (yellow) metals. Type K is the industry standard for EGT/TIT, but some manufacturers spec Type K for use in digital and/or amplified CHT indicators.

EGT Type E – Type E thermocouples are constructed with red (-) and brown (+) wires. Type E thermocouples are made of chromel and constantan metals. Type E thermocouples are of an older technology and produce twice the millivolts of a Type K system.

Important: Type E and Type K components should not be mixed. Choose based on the type of indicator and leads installed in the aircraft.

EGT Type E thermocouples are no longer available. The information contained on this website for Type E thermocouples is for reference only.

Ungrounded Thermocouples – In an ungrounded thermocouple, wires in the element are welded to each other, but not to the shaft. The thermocouple wire junction is isolated from the rest of the outer sheath and the wires must maintain a certain insulation resistance value to work correctly. This is also referred to as an isolated tip. Therefore, there is no continuity in an ungrounded thermocouple. Alcor offers a one-year warranty on ungrounded thermocouples.

Clamp Style: Clamp style thermocouples are the most common type of EGT/TIT probe and are available in Type K and Type E. These thermocouples can also be found as grounded and ungrounded options.

Screw-In Style: Screw-in style thermocouples are available for EGT/TIT probes and are available in Type K and Type E. These thermocouples can also be found as grounded and ungrounded options. Alcor screw-in thermocouples are available in 7/16”-20 thread size (common on Continentals) or 1/4” NPT (common on Lycoming’s).

Bayonet Style: Bayonet style thermocouples are available for CHT in Type K and Type J. These style thermocouples twist and lock into a screw-in adapter (28202). Bayonet style thermocouples are most commonly used on engine models equipped with threaded receptor and/or bayonet adapter installed in cylinders.

Gasket Style: Gasket style thermocouples are available for CHT in Type J and no adapter is required. The 18mm adapter fits on all standard aviation spark plugs offered from Tempest and others. Gasket style thermocouples are primarily used on engines not equipped with threaded receptor and/or bayonet adapter in the cylinders.

RTD (Resistance Thermistor Device): An RTD is a different type of sensor that measures resistance, as opposed to millivolts, and acts more like an ohm meter. Alcor manufactures RTD P/N AA86146, which has identical specifications to AN5546-1.