Oscillators – With device responsive to external physical condition
Patent
1987-07-13
1988-07-19
Grimm, Siegfried H.
Oscillators
With device responsive to external physical condition
264 23, 264 401, 4251742, 324 711, 331154, 331183, B29G 700, H03B 500
Patent
active
047588039
ABSTRACT:
Changes in the ultrasonic properties of fiber-reinforced plastics during the curing process are monitored by a marginal oscillator to determine the degree of cure. The plastic sample and transmitting and receiving transducers serve as a narrowband acoustic resonator and are placed in the feedback loop of a variable gain amplifier; using gain control the system is allowed to marginally oscillate. The resonant frequency of the sample and amplifier gain are related to the velocity and attenuation of sound in the plastic and are determined by measuring the received signal frequency and amplifier gain control voltage. The system has frequency locking means to track changes in resonant frequency during the cure cycle.
REFERENCES:
patent: 3791792 (1974-02-01), Lindsay
patent: 4455268 (1984-06-01), Hinrichs et al.
W. P. Winfree, F. R. Parker, "Measurement of the Degree of Cure in Epoxies With Ultrasonic Velocity", Rev. of Progress in Quant. NDE, 1985, vol. 5B, Plenum Press.
D. R. Dietz, "Ultrasonic Detection of Microemboli: Physical Principles and Physiological Results", Ph.D.Thesis, Washington Univ., 1976, pp. ii, iii, 35-92, 147-151, 157-159.
M. S. Conradi, J. G. Miller, J. S. Heyman, "A Transmission Oscillator Ultrasonic Spectrometer", Rev. Sci. Instrum., 45, 358-360, Mar., 1974.
Campbell Donald R.
Davis Jr. James C.
General Electric Company
Grimm Siegfried H.
Webb II Paul R.
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