Omega-engineering OMEGASCOPE OS533 User Manual download pdf (Page 70)

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Appendix: Determining an Unknown Emissivity

In Appendix A, we showed how emissivity is an important

parameter in calculating the temperature of an object via infrared

means. In this section we discuss how to determine a specific

emissivity value. If you know the material of the object, use Table B-

1 in Appendix B to look up its approximate emissivity. Most organic

materials such as plastics, cloth, or wood have an emissivity of

about 0.95. For this reason, we use 0.95 as the default emissivity

setting in the OS530 Series Thermometer.

For objects of unknown material or for very precise measurements,

use one of the following methods to determine a specific emissivity

value.

Method 1

1. Measure and record the temperature of the object using a contact

temperature probe such as a thermocouple or RTD.

2. Aim the thermometer at the object.

3. Adjust the emissivity until the temperature reading of the

thermometer equals the temperature measured in Step 1.

Method 2

1. Heat the object (or at least a sample of the object material) on top

of a heating plate to a known temperature. Make sure the

thermometer and the air surrounding the heating plate are at the

same temperature.

2. Measure the temperature of the object material with the

thermometer. Make sure that the object fills the FOV of the

thermometer.

3. Adjust the emissivity until the temperature reading of the

thermometer equals the known temperature of Step 1.

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Omega-engineering OMEGASCOPE OS533 User Manual Page 70