Fluke Ti20 User Manual download pdf (Page 58)

Ti20

Users Manual

B-2

0.1 A 1 A 1 UA 100 A

0.6 0.8 1 1.5 2 3 4 6 8 10 15 20 300.4

1 µ 10 µ 100 µ 0.1 cm 1 cm 10 cm 1 m 10 m 100 m 1 km 10 km 100 km

Wavelength

Visible

Wavelength µm

Gamma

Rays

X-Rays Ultraviolet Infrared

Infrared Measurement Region

Radio

EHF SHF UHF VHF HF MF LF VLF

0.1 µ

dag011f.eps

Figure B-1. Infrared Measurement Region

Q. How to assure accurate temperature measurement?

A. A solid understanding of infrared technology and its principles lies behind accurate

temperature measurement. When the temperature is measured by a non-contact device the

IR energy emitted from the measured object passes through the optical system of the

thermometer or thermal imager and is converted to an electrical signal at the detector.

This signal is then displayed as a temperature reading and/ or thermal image. There are

several important factors that determine accurate measurement. The most important

factors are emissivity, distance to spot ratio, and field- of-view.

Q. What is emissivity?

A. All objects reflect, transmit and emit energy. Only the emitted energy indicates the

temperature of the object. When IR thermometers or thermal imagers measure the surface

temperature they sense all three kinds of energy, therefore all thermometers have to be

adjusted to read emitted energy only. Measuring errors are often caused by IR energy

being reflected by light sources.

Some IR thermometers and thermal imagers allow you to change the emissivity in the

unit. The value of emissivity for various materials can be looked up in published

emissivity tables.

Other units have a fixed, pre-set emissivity of 0.95, which is the emissivity value for most

organic materials and painted or oxidized surfaces. If you are using a thermometer or

thermal imager with a fixed emissivity to measure the surface temperature of a shiny

object you can compensate by covering the surface to be measured with masking tape or

flat black paint. Allow time for the tape or paint to reach the same temperature as the

material underneath. Measure the temperature of the taped or painted surface. That is the

true temperature.

1 2 ... 53 54 55 56 57 58 59 60 61 62 63 ... 67 68

No comments

Fluke Ti20 User Manual Page 58