Method and apparatus for reducing signal-phase error in induction well logging instruments
US5600246A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Nov 28, 1995 |
| Grant date | Feb 4, 1997 |
| Priority date | — |
| Expiry date | Nov 28, 2015 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01V3/28
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
An apparatus for calibrating phase response of a receiver in an induction well logging instrument. The apparatus includes a source of alternating current selectively coupled to a transmitter. A low-gain antenna is disposed proximal to the transmitter for generating voltage in response to a magnetic field generated by the alternating current in the transmitter. The instrument includes a receiver spaced apart from transmitter. A phase comparator is coupled at one input to the low-gain antenna and at its other input to the source of alternating current. The phase comparator generates a signal corresponding to phase difference between the voltage in the low-gain antenna, and the alternating current. A sample and hold circuit is coupled to phase comparator for retaining the most recent signal from the phase comparator. A time-delay circuit is coupled to the source of alternating current and to the sample and hold circuit. The time-delay circuit output consists of the alternating current time-shifted by an amount corresponding to the difference in phase. A current switch is interconnected between the output of the delay line and the receiver for selectively injecting the time-shifted alt…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.