GB1110156A - - Google Patents

Abstract

1,110,156. Vibration testing. TEXTRON ELECTRONICS Inc. 2 June, 1966 [21 June, 1965], No. 24721/66. Heading H4D. In a vibration testing system in which the exciter 22 (Fig. 1) is driven by a signal produced by combining the outputs of a bank of AGC amplifiers 16 fed from respective ones of a bank of bandpass filters 15 supplied from an audio frequency random noise generator 10 and the gains of the amplifiers 16 controlled by the outputs of respective ones of a further bank of bandpass filters 30 (similar to 15) supplied with input signals derived from an accelerometer 24 coupled to the exciter 22 to control the acceleration spectral density characteristic so that it is independent of resonance effects in the system or specimen as described in Specification 927,195, compensation for the effect of the mechanical impedance of the specimen under test is effected by additionally controlling the gains of the amplifiers 16 by signals derived from a force transducer 35 mounted on the exciter 22. The signals from the latter are converted to the same frequency range as utilized for the forward exciter drive signals and the control signals from the accelerometer by means of a balanced modulator 38 fed from the local oscillator 13 the output of the latter being supplied via a bank of adjustable phase shifters 40 and a bank of adjustable attenuators 42 and thence via respective ones of a bank of summing amplifiers 29 together with the signals derived from the accelerometer to the bank of band-pass filters 30.