Geophysical Systems Corporation

California Institute of Technology

Massachusetts Institute of Technology

James A Westphal

J Robert Fort

Donald R Juilfs

C Hewitt Dix

Michael A Carr

Thomas B McCord

Apparatus is described for positioning a tilt meter (12) in a horizontal plane (14) and maintaining it horizontal despite temperature changes, with greater precision than heretofore. Leveling screws 25-27 which hold the upper surface (18) of a base member (16) precisely horizontal, are engaged with nuts (21-23) attached to the base member, where the nuts are made of the same material as the screws, to eliminate tilting of the base member with temperature changes, due to different nuts engaging a screw at a different height. The nuts are attached to the upper surface (18) of the base member, to further avoid imprecision. The curved glass bubble tubes (60) are mounted in V-grooves (80) in four point contact therewith.

Positioning device

A tilt meter comprises two tilt sensors (110 and 110S, see FIG. 7) in a housing (105). Each sensor acts as two variable resistors (R.sub.s), which together with two fixed resistors (R.sub.F) form a Wheatstone bridge (25), driven by a square wave signal from a drive source (30). The output of the bridge is fed to an electronic circuit (35) which includes a synchronized switch (43) to cut out the spikes (50), which the bridge outputs at the transitions of the square wave. The output of the electronic circuit is a DC signal, whose amplitude indicates tilt magnitude and polarity indicates direction of tilt. The housing (105) is supported on a support surface (102S) by means of 15 legs (116, 117) threaded into nuts of the same metal, and which has a very low thermal coefficient of expansion.

Tilt meter

This abstract describes a system for the field recording of seismic data in which a plurality of geophone outputs are connected to an array terminal. Each geophone is connected to a fixed gain differential amplifier of high gain. The outputs of the amplifiers are square wave and each output goes to one of the parallel inputs of a parallel to serial convertor, through gate means. On a first command from an array controller in a distant recording truck, the gate means are momentarily opened, to store a single bit in each channel corresponding to the sign of the square wave, in the convertor inside the array terminal. The convertor then reads out as a train of serial bits, the stored pulses. This train of single bit signals is carried to the array controller through each of the other array terminals by a single pair of conductors, and stored on a magnetic recording means.

Data acquisition, transport and storage system

This abstract describes a system for acquisition of analog signals at a plurality of sensors, carrying these signals in groups of M channels to each of N spaced-apart array terminals, processing each signal in the array terminals by separately amplifying, digitizing to 1 bit and storing as single bit pulses, one for each channel, in a parallel to serial convertor. Each of the convertors in each of the array terminals are operatively connected in series and to an array controller, which also controls a disc magnetic recorder. On command, the convertors are read out in series as sequential trains of M bits into core memories and then stored on the disc. Successive, bit samples at subsequent digitizing intervals are stored on the disc, to form a first record. Subsequent records are processed, stored in core memory and composited with previous records stored on the disc.

Data compositing and array control system

This abstract describes a system for the field recording of seismic data in which a plurality of geophone outputs are connected to an array terminal. Each geophone is connected to a fixed gain differential amplifier. A shifting function is produced which is added to the amplified geophone signal to form a sum signal which goes to an axis crossing coder, (AXC). On a first command from an array controller in a distant recording unit, the AXC is commanded to produce axis-crossing-coded pulses of the instantaneous sum signals. These pulses are stored in a parallel-to-serial converter inside the array terminal. On a second command from the array controller the converter reads out as a train of serial bits, the pulses stored in the converter. This train of single bit signals is transmitted to the array controller by a single pair of conductors, and stored on a magnetic recording means.

A system for the field recording of seismic data in which a large plurality of geophones are arrayed on the earth and divided into groups, and each group is connected to an array terminal. All of the array terminals are connected in series, by cables, with the last terminal connected to a recording unit. In each of the terminals there are means to process the geophone analog signals by amplifying at constant gain and digitizing to 1 bit to provide a plurality of 1 bit pulses, which are stored in parallel in a parallel to serial convertor. On command from the recording unit, the bits stored in the convertors are read out in series and are transmitted by a pair of signal conductors to the next in series terminal for storage in the convertor, and from there to the convertor in the next in series terminal, and so on, until all of the bits stored in each of the terminals are transmitted as a plurality of short trains of single bit signals, to the recording unit, where they are recorded on a magnetic digital storage means. Each of the array terminals has an address register in which an address is stored, which is transmitted as a heading to the data stored in that convertor.

Data array network system

This abstract describes a system for acquisition of analog signals at one or more sensors, carrying these signals in groups of M channels to each of N spaced-apart array terminals, processing each signal in the array terminals by separately amplifying, adding to a shifting signal of selected amplitude, axis-crossing-coding these sum signals and storing as single bit pulses, one for each channel, in a parallel to serial converter. Each of the converters in each of the array terminals are operatively connected in series and to an array controller, which also controls a disc magnetic recorder to run at constant speed. The disc generates a disc clock, and responsive to the disc clock the converters are read out in series as a sequential train of MN bits and stored on the disc. Successive samples at subsequent digitizing intervals are stored on the disc, to form a first record. Subsequent records can be processed, coded and recorded, and composited with previous records on the disc.

A device for replacing a fluorescent lamp in a two lamp serially connected fluorescent fixture either of the type which includes a rapid-start type transformer for every two rapid-start fluorescent lamps or an instant start fixture for every two instant start lamps. By placing the device in the fixture in place of one of the two lamps the remaining lamp is energizable to provide illumination, whereas without the device the remaining lamp is inactive.

Device for replacing a fluorescent lamp in a serially connected

A long exposure photometer-digitizer operative in an integration mode to receive weak illumination as from celestial observations through a telescope or from field or laboratory observations of objects and to provide a recorded digital representation thereof. A silicon, vidicon illumination sensor is employed to provide a wide dynamic range, sensitive and linear response over a large spectral region. Cumulative photon interaction with the vidicon tube during a long exposure is achieved by operating the vidicon at a reduced temperature which minimizes dark current effects and promotes integration mode operation. After a predetermined vidicon exposure interval the image electrically stored in the target is read out by a scanning electron beam, digitized and recorded to provide an immediately available digital record of the object. The target is sensitized before each exposure.

Photometer-digitizer system

This abstract describes a system for the field recording of seismic data in which a large plurality of geophones are divided into groups and each group is connected to an array terminal. All of the array terminals are connected in series, by cables, with the last terminal connected to a recording unit. In each of the terminals there are means to process the geophone analog signals by amplifying and adding them to a selected shifting function, and axis-crossing-coding (AXC) the resulting sum signals to provide a plurality of pulses which are stored in a prallel-to-serial converter. In addition, each of the terminals contains a buffer register. On command from the recording unit the bits stored in the converters are read out in series and are transmitted by a pair of signal conductors to the next in series terminal for storage in the buffer register, and from there to the buffer register in the next in series terminal, and so on, until all of the bits stored in each of the terminals are transmitted as a continuing train of single bit signals to the recording unit, where they are recorded on a magnetic disc. Each of the array terminals has a hard wired address code which is transmitted as a heading to the data stored in that converter. Logic circuit means are provided to identify, for each terminal, which of the plurality of cable ports in the terminal are occupied by cables, and which of the cable ports is the one by means of which the commands are received from the recording unit.

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Altadena, CA, United States of America

James A Westphal