| 摘要 |
1,221,747. Frequency response plotter. B. R. COLEMAN. 28 March, 1969 [29 March, 1968], No. 16346/69. Heading B6P. [Also in Division G4] A device for calculating the overall frequency response curve of a control system for either amplitude ratio or phase shift comprises a sheet of graph paper 13 on which frequency response curves W, X and Y for the components are plotted using templates and a three-part slider 14 by which the values of curves W, X, Y may be added algebraically to plot the overall frequency response of the system. The frequency is plotted logarithmically on the base axis, amplitude ratio in decibels on the left-hand axis, and phase shift on the right. A conversion scale 42, with a transparent cursor 43, converts the ratio in decibels to normal amplitude ratio. To plot the individual curves for the components, the slider 14 is removed and a straight edge (not shown) pinned to the bottom edge of the base 11. A template, representing the transfer function of the appropriate component, is positioned on the paper 13 with a reference edge against the straight edge and a curve drawn. In another template (Fig. 5, not shown) a vertical line is aligned with the corner frequency (i.e. frequency of maximum amplitude ratio and/or phase shift), a left end aligned with the zero decibel line, and the curve drawn from the template edge. The template can be rotated through 180 degrees to reverse the polarity of the curve. The curves W, X, Y for amplitude ratio and/or phase shift are plotted using the appropriate templates then the straight edge is removed and the slider 14 placed on base 13. The slider comprises a first frequency slide 15 having spring-loaded bars 18, 19 gripping the edge of the base. A second totalizer slide 24 is mounted on rails 17 on the first slide so that it can move with respect to slide 15 and includes a spring-loaded adjustable index mark 28. A third adder slide 31 is slidably mounted on the slide 24 against the action of a spring 35. The slide 31 has a spring-mounted upper part 36 including an inkwell 37 and a pen 39 so that the graph paper can be marked by pressing part 36 down against its spring. To plot the overall response, slide 15 is adjusted so that pen 39 is over the desired frequency then slide 24 is moved till index 28 is over the zero decibel line for amplitude ratio. Adder slide 31 is moved, keeping the other slides still, till the pen intersects one curve. Then slide 24 is moved till the pen 39 intersects the zero decibel line (slides 24 and 31 not being relatively moved). Then the adder slide 31 is moved up to the next curve and the process repeated for all the curves until the last one when the index 28 is aligned with the zero decibel line and the final position of pen 39 marked on the paper. This process is repeated for the other frequencies to get the overall frequency response curve Z. The templates and other components are made of a transparent plastics material. |
