Exhaust Thermocouple Design
Exhaust gas temperature sensors are usually thermocouples due to the very high temperatures involved. Often 800°C or more can be achieved.
High Vibration Environment, Fast Response, Corrosion Resistance
The primary requirement of an Exhaust Gas Thermocouple is to be robust enough to survive a high vibration environment. After that it must be small enough to respond quickly and not disrupt gas flows. The exhaust thermocouple needs a gas seal and sheath to protect it from the corrosive combustion products.
Making probes robust enough usually means building them from mineral insulated cable. This is a very tough product. The cable can go directly into the gas stream, or can have a secondary stainless sheath to toughen it up even more. Mineral Insulated cable can be easily bent to suit the required route around the engine.
Protection sheaths are usually a high chrome stainless. Something like 446SS or 310SS are often suited. Applications below 800°C may use cheaper grades.
Gas seals are either threads welded to protection sheaths or compression fittings, which screw into the manifold.
Exhaust Thermocouple Projects
We supply custom made exhaust gas temperature sensors for engines, sports cars, trucks and buses. Our sensors are an integral part of systems used to reduce large vehicle exhaust pollutants which then allows them to enter low pollution areas such as London’s LEZ – Low Emmission Zone.
Example Exhaust Gas Thermocouple
The exhaust gas thermocouple below includes some signal conditioning electronics to produce a linear mV output at a much higher voltage than would normally be expected of a thermocouple. The temperature sensor is used with a compression fitting to form a gas seal.