There are two types of pyrometers: optical (monochromatic or narrowband) and radiation (total radiation or broadband) pyrometers.
The last devices originally were called radiation pyrometers, then radiation thermometers, and more recently infrared thermometers. However, the first their name (radiation pyrometers) is still widely used at present. These devices have high accuracy of ±0.01 °C as a standard instruments, and from ±0.5 to ±1% for industrial purposes.