Alberta Boilers Safety Association (ABSA) Practice Test

In an optical pyrometer, what type of comparison is made to measure temperature?

1. Radiation

2. Contrast

3. Brightness

4. Voltage

The correct answer is: Brightness

An optical pyrometer measures temperature by comparing the brightness of the object being measured to the brightness of a reference light source. This principle is based on the fact that an object's brightness increases with its temperature, allowing for a direct correlation between the two. The device typically has an adjustable visual reference that can be adjusted to match the observed brightness of the target object, enabling the user to estimate the object's temperature. While the other factors such as radiation, contrast, and voltage may play roles in different instruments or contexts, the core function of an optical pyrometer specifically revolves around the concept of comparing brightness levels. This is fundamental to its design and operation, making it effective for non-contact temperature measurement, especially at high temperatures where traditional thermometric methods may be less viable.