Communications: electrical – Selective – Interrogation response
Patent
1976-09-29
1978-07-11
Birmiel, Howard A.
Communications: electrical
Selective
Interrogation response
318314, 318318, 340 18NC, G01V 140
Patent
active
041005287
ABSTRACT:
A measuring-while-drilling system has a digitally implemented motor speed control circuit for controlling a downhole, motor-driven acoustic signal generator. The acoustic generator is motor driven at speeds for imparting to well fluid an acoustic signal having phase states representative of encoded data derived from measured downhole conditions. The digital motor control circuit drives the motor at a substantially constant, carrier frequency producing speed in the absence of data of one logic state and temporarily changes the speed of the motor to effect a predetermined phase change in the carrier signal upon data of the predetermined logic state. For returning the motor speed to the carrier frequency producing speed during phase changes, the digital motor control circuit includes a first digital integrating circuit for providing a first digital signal having a value indicative of the constant value of the carrier frequency integrated over a time period beginning substantially upon the occurrence of the particular data; it has a second digital integrating circuit for providing a second digital signal having a value indicative of the instantaneous speed of the acoustic generator integrated over the time period; and it has a digital comparator which is responsive to the first and second digital signals for generating a control signal effective to change the speed of the motor when the difference between the first and second digital signals reaches a predetermined value.
REFERENCES:
patent: 3176208 (1965-03-01), Gifft
patent: 3331006 (1967-07-01), Strand et al.
patent: 3789355 (1974-01-01), Patton
patent: 3820063 (1974-06-01), Sexton et al.
patent: 3828234 (1974-08-01), Goldberg
patent: 3950682 (1976-04-01), Dohanich, Jr.
patent: 3974428 (1976-08-01), Hafle
Bernard James I.
Strom Gerald A.
Birmiel Howard A.
Moore Stewart F.
Moseley David L.
Schlumberger Technology Corporation
Sherman William R.
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