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Priority claimed from US06/687,075external-prioritypatent/US4698792A/en
Priority claimed from US06/687,074external-prioritypatent/US4703460A/en
Application filed by Schlumberger LtdfiledCriticalSchlumberger Ltd
Priority claimed from EP85402443Aexternal-prioritypatent/EP0188936B1/en
Application grantedgrantedCritical
Publication of ATE69654T1publicationCriticalpatent/ATE69654T1/en
Method and device for determining the first arrival times of compression waves of the waveform passage of a threshold value supplied by a device in an acoustic downhole tool.