The Frequency Response of Pneumatic Lines

Abstract

The amplitude frequency response (transfer gain curve) of 0.170-in-ID blocked pneumatic lines of the type used in fluidic systems was experimentally determined. Several lengths (20 ft and less) of tubing at several mean pressures (10 to 40 psig) were studied over the frequency range of 1-1000 cps. The electric-pneumatic analogy was used to develop theoretical predictions of the gain curves. Correlation with experiment showed that a frequency-dependent resistance and a frequency-dependent conductance were required in the analogy when the signal frequency was somewhat greater than a characteristic frequency of the line. A high-frequency model, based on the work of Nichols, was developed; it predicted the resonant gains within 2 db and the resonant frequencies within 10 percent.