GB906659A - - Google Patents

Abstract

906,659. Voltage measurement SCHLUMBERGER WELL SURVEYING CORPORATION. July 29, 1960 [Aug. 3, 1959], No. 26516/60. Class 37. [Also in Group XL (c)] Acoustic well-bore logging apparatus is characterized by an electric circuit responsive to a selected half-cycle of the received signal to supply to a recorder a signal corresponding to the peak amplitude thereof. The output of magnetostrictive receiving transducer R2 is fed to a pulse generator 31 having a bias control circuit (not shown) coupled to a surface sensitivity control 17 adjusted above the peak level of the first half-circle of the amplified receiver output but below the expected peak level of the second half-cycle; errors due to low amplitude noise are thus avoided. Generator 31 is controlled also by a gate circuit (not shown) which applies a pulse to the generator immediately prior to the earliest possible arrival of a transmitted sound pulse at transducer R2. Peak voltage measuring circuit 40 remains inoperative until generator 31 produces a pulse to trigger multivibrator 42. Measuring circuit 40 comprises a normally-conducting triode 55 such that cathode follower 51 output is insufficient to cause diode 56 to conduct; the multivibrator produces a pulse to cut-off triode 55 for the second half cycle of the received wave. The time constants circuits 57, 58 and 61, 63 are made sufficiently long to ensure that the peak voltage is recorded. Transistor pulse circuits, Fig. 3. In an alternative peak voltage measuring circuit monostable multivibrator 81 is triggered by generator 31 to gate the receiver output via amplifier 68 in series gating circuit 77, 80 the output from which is applied to cathode follower 91 via current-amplifying transistor 83a which charges capacitor 86 via diode 85.