Pyrometers are used to measure the exhaust gas temperature, or EGT, of a diesel engine. Diesel vehicles are generally not equipped with pyrometers and thus must be installed separately.
Extremely high temperatures can cause damage to an engine, and the pyrometer helps the motorist to monitor the exhaust gas temperature. Pyrometers are able to measure temperatures much higher than normal thermometers, and generally display in degrees Fahrenheit.
A pyrometer is composed of thermocouple, which is a probe that is of particular importance because it is the instrument used to measure the temperatures. The probe does not actually touch the area intended to be measured, but rather it is mounted on a location of proximity, from where it measures the exhaust gas temperature. If the combustion through the cylinders is too hot, it creates what is called afterburning and can be damaging to the vehicle. Additionally, airflow can be restricted, which then causes problems with the amount of oxygen that is able to pass through the cylinders. The pyrometer can alert the vehicle operator of impending problems, and thus can save the engine from serious damage. Lastly, normal EGTs depend on the type of diesel vehicle. They may range from 1,000 to 1,300 degrees Fahrenheit; temperatures below these indicate the efficiency of the engine.