A Frequency Modulation Pressure Recording System

Abstract

A simple frequency‐modulated pressure gauge employing a variable capacity pick‐up element has been devised to measure the oscillating pressures of burning gases. It has been used to measure pressures in pulse jet engines ranging from −5 to +60 p.s.i. gauge, under conditions where the gas temperatures ranged from approximately 300°K to 2450°K and the gauge mount vibrated with an amplitude of approximately 0.125 inch. The fundamental frequencies of temperature variation, pressure variation and mechanical vibration were 40 cycles and 220 cycles per second. Under these conditions the pressure response is essentially linear from 0 to 5500 cycles per second.