Ultrasonic system for measuring dimensional or stress change in structural member
Pseudo continuous wave instrument
Pulsed phase locked loop strain monitor Patent #: 4363242
ApplicationNo. 06/342901 filed on 01/26/1982
US Classes:73/579, Resonance, frequency, or amplitude study73/761Threaded fastener stress
ExaminersPrimary: Birmiel, Howard A.
Attorney, Agent or Firm
International ClassesG01L 5/24 (20060101)
G01L 1/25 (20060101)
AbstractA first signal at a first frequency which is a selected harmonic of the resonant frequency of a bolt in a first loaded condition is determined. Then there is determined a second signal at a second frequency being the same harmonic of the resonant frequency of the bolt in a second loaded condition. Both frequencies are multiplied by a factor M. The up input of a counter receives one of the signals for a predetermined duration, and the down input receives the other signal for the same duration. The number of pulses remaining in the counter is representative of the difference in load between the first and second loaded conditions.