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Down hole apparatus for sensing and storing values of physical parameters
| Details |
Inventors: Clark, Kenneth K.; Harper, James C.;
Assignee: Geophysical Research Corporation (Tulsa, OK)
Primary Examiner: Myracle; Jerry W.
Assistant Examiner:
Attorney, Agent or Firm: Head, Johnson & Chafin
Apparatus for digitally recording the value of pressure and temperature, or other parameters, in a borehole logging instrument. In one embodiment the values of the earth parameter are converted to an A.C. signal, the frequency of which is a function of the value of the parameter. Clock means are provided for presenting, at selected time intervals, voltage pulses of selected short time length. The A.C. signal is gated to a counter for the selected short interval of time, and the count of the counter becomes a measure of the parameter. Solid state memory means are provided, and the output of the counter in the form of binary bits is stored in the memory. Means are provided for retrieving the instrument and reading out of the memory the binary bits as stored. |
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DETAILED DESCRIPTION It is a primary object of this invention to provide a subsurface, self-contained, self-powered, instrument which has sensors which are sensitive to earth parameters in a deep borehole and which provide electrical signals which vary in accordance with the variation of the values of the parameters.
It is a further object to detect the electrical signals and convert them to digital values, which are stored in solid state memory apparatus in the instrument.
It is a still further object to provide means to cause the instrument to make records of the selected parameters at time intervals, of selected magnitude, in the ranges of minutes, hours or days.
The parameters of pressure and temperature are the ones of most interest at the present time and, accordingly, means are provided in the logging instrument for converting these parameters to variable frequency electrical signals, the frequency of which is a function of the value of parameters.
Means are provided for accepting at least two different parameters each creating electrical signals of different frequencies.
Electronic switching means are provided, on command, to switch one or the other signal to an electronic digitizer which measures the frequency of the signal and converts it to a digital number which is stored in one of a plurality of storage cells in a solid state digital memory.
clock means are provided for making such digital measurements at selected intervals of time which are pre-selected prior to lowering the instrument into the borehole.
When the instrument is retrieved the data stored in the digital memory are retrieved and the digital values are converted to analog values of the parameters, and are displayed or recorded.
The system of this invention is not limited in the smallest values of pressure and temperature which it can measure, as are the prior art instruments, which depend on mechanically, analog-wise, recording the variation of pressure and temperature by means of a stylus on a moving recording chart
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