Mặc dù tần số là một phần rất quan trọng của thông tin liên quan đến trục trặc máy móc thiết bị cô lập, nó chỉ là một phần của bức tranh tổng thể. Nó là cần thiết để đánh giá tất cả các dữ liệu trước khi đến một kết luận. Biên độ Biên độ đề cập đến giá trị tối đa của một chuyển động hoặc rung động. | 176 An Introduction to Predictive Maintenance Figure 8-4 Electromagnetic spectrum. Basic Infrared Theory Infrared energy is light that functions outside the dynamic range of the human eye. Infrared imagers were developed to see and measure this heat. These data are transformed into digital data and processed into video images called thermograms. Each pixel of a thermogram has a temperature value and the image s contrast is derived from the differences in surface temperature. An infrared inspection is a nondestructive technique for detecting thermal differences that indicate problems with equipment. Infrared surveys are conducted with the plant equipment in operation so production need not be interrupted. The comprehensive information can then be used to prepare repair time cost estimates evaluate the scope of the problem plan to have repair materials available and perform repairs effectively. Electromagnetic Spectrum All objects emit electromagnetic energy when heated. The amount of energy is related to the temperature. The higher the temperature the more electromagnetic energy it emits. The electromagnetic spectrum contains various forms of radiated energy including X-ray ultraviolet infrared and radio. Infrared energy covers the spectrum of micron to 100 microns. The electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength. A wave has several characteristics Figure 8-5 . The highest point in the wave is called the crest. The lowest point in the wave is referred to as the trough. The distance from wavecrest to wavecrest is called a wavelength. Frequency is the number of wavecrests passing a given point per second. As the wave frequency increases the wavelength decreases. The shorter the wavelength the more energy contained the longer the wavelength the less energy. For example a steel slab exiting the furnace at the hot strip will have short wavelengths. You can feel the heat and see the red
