Fundamentals of Measurement Technology (13) Prof Wang Boxiong
Fundamentals of Measurement Technology (13) Prof. Wang Boxiong
5.4.3 Types of filters 1. Low-pass filters e C (a) Electrical K (b) Mechanical /se k psI/in n psI ARA (c)Hydraulic Fig. 5.40 Low-pass filters
5.4.3 Types of filters 1. Low-pass filters Fig. 5.40 Low-pass filters
5.4.3 Types offilters · RC lower- pass filter de Rc-o+e =e dt (5.63) H +1 (5.64) where the frequency f=_1 2TRO corresponds to the point of amplitude attenuation of -3dB, and is the upper cut-off frequency
5.4.3 Types of filters • RC lower-pass filter o i o e e dt de RC + = ( ) 1 1 ( ) + = = s s e e H s i o (5.63) (5.64) where the frequency RC f 2 1 = corresponds to the point of amplitude attenuation of –3dB, and is the upper cut-off frequency
5.4.3 Types offilters H(f) For simple first-order systems, the attenuation √2 is quite gradual with frequency 6dB/octave 1/2πr By adding more"stages P(f) 1/2xr 0 (see Fig. 5.42(a)the 45 sharpness of cutoff may be increased. But the 0)° disadvantage: loading effects should be take Fig. 5.41 Amplitude and phase characteristics of the first-order Into account low-pass filters
5.4.3 Types of filters For simple first-order systems, the attenuation is quite gradual with frequency,6dB/octave. By adding more “stages” (see Fig.5.42(a))the sharpness of cutoff may be increased. But the disadvantage: loading effects should be take into account. Fig. 5.41 Amplitude and phase characteristics of the first-order low-pass filters
5.4.3 Types offilters Many electrical filters are active devices based on op-amp technology. Passive filters have very low noise, require no power supplies, and have a wide dynamic range: Active filters are much more adjustable and versatile, can cover very wide frequency ranges, have very high input and very low output impedances, and can be configured for simple switching from low-pass to high-pass and combination for band-pass or band-reject behavior
5.4.3 Types of filters Many electrical filters are active devices based on op-amp technology. Passive filters have very low noise, require no power supplies, and have a wide dynamic range; Active filters are much more adjustable and versatile, can cover very wide frequency ranges, have very high input and very low output impedances, and can be configured for simple switching from low-pass to high-pass and combination for band-pass or band-reject behavior