Product Details
Product Description
Product Description
Focus on DCS, PLC, robot control system and large servo system.
Main products: various modules / cards, controllers, touch screens, servo drivers.
Advantages: supply of imported original products, professional production parts,
Fast delivery, accurate delivery time,
The main brands include ABB Bailey, Ge / fuanc, Foxboro, Invensys Triconex, Bently, A-B Rockwell, Emerson, ovation, Motorola, xyvom, Honeywell, Rexroth, KUKA, Ni, Deif, Yokogawa, Woodward, Ryan, Schneider, Yaskawa, Moog, prosoft and other brands
You can set the cutoff frequencies of filters in the SCXI-1141/1142/1143 module by using the external clock input in applications that require external control of the cutoff frequency or that require finer resolution than the module provides internally. The cutoff frequency for each filter using the external clock as a base is: fext/(100 × n) where fext is the frequency of the external clock and n is an integer you select such that 2 ≤ n ≤ 216. When the frequency of the external clock changes, the cutoff frequency changes proportionally. An external clock can control the SCXI-1141/1142/1143 module filters because they use a switched-capacitor architecture, which uses analog sampling. However, this technique is also susceptible to aliasing in much the same way as the digital sampling of a DAQ device (with a Nyquist frequency of one-half the external clock frequency). Analog sampling also creates high-frequency images of the signal because the output waveform has a staircase shape. The SCXI-1141/1142/1143 module prevents these errors by using sets of prefilters and postfilters that do not sample the signal. A different set of prefilters and postfilters is used for each of 12 ranges of input frequencies. The prefilters reduce signals that can alias into a lower frequency by at least 40 dB, and the postfilters reconstruct the output waveform, reducing high-frequency images to at least –80 dB. NI software automatically chooses the correct set of prefilters and postfilters when you specify a cutoff frequency. However, when the external clock input is used to set the cutoff frequency of a filter, you must still supply an approximate cutoff frequency so that the software can determine the appropriate set of prefilters and postfilters. Table 4-1 gives the ranges of cutoff frequencies that the prefilters and postfilters use.