振动分析和仪器的艺术达芬奇.pptVIP

Communications Area of Greatest Technology Progress Email, FTP, Internet (High Speed) Industrial Ethernet Wireless Phone, Modem, Ethernet Satellite Digital Revolution! (Remote Desktop) Communications Analysis and Diagnostics Area of LEAST Progress Not Fundamentally Changed in 20 years Personnel Downsizing – not going to come back, either What is a Vibration Analyst’s Career Path? In-house are becoming contracted services Constant re-training to solve yesterday’s problems! Analysis and Diagnostics Will Technology come to the Rescue? Remote, centralized Diagnostics Rapid Service Company Growth Rapid Growth in Wireless Sensor Technology has Cooled Power Supply Problem Spawned new VC-backed Research Companies Anti-Aliasing Filters What are they and why do I need them? Because “false Frequencies” are displayed when Aliasing is present in a system. The maximum frequency component a sampled data system can accurately handle is its Nyquist limit. The sample rate must be greater than or equal to two times the highest frequency component in the input signal. When this rule is violated, unwanted or undesirable signals appear in the frequency band of interest. Aliased Signals In old western movies, as a wagon accelerates, the wheel picks up speed as expected, and then the wheel seems to slow, then stop. As the wagon further accelerates, the wheel appears to turn backwards! In reality, we know the wheel hasnt reversed because the rest of the movie action is still taking place. What causes this phenomenon? The answer is that the shutter frame rate is not high enough to accurately capture the spinning of the wheel.  Aliased Signals False low-frequency sin wave… Caused by sampling too slowly Violated the Nyquist Criterion Anti-Aliasing Filters What are they and why do I need them? Generally they are low-pass filters that do not pass frequencies above the ADC’s range. Here is a representation of an IDEAL filter… Real Anti-Aliasing Filters Trade-offs: Elliptic, Chebyshev, Butt