Means and method for recording seismic signals

#The present system and method relates to amplifying systems and methods in general and, more particularly, to a floating point amplifier system and method.

#A seismic system includes an amplifying channel which receives a wide dynamic range input signal. The amplifying channel provides amplified signals having different amplitudes corresponding to the input signal. Comparators compare each amplified signal, except for the least amplitude amplified signal, with reference signals corresponding to a predetermined range for an output signal. The comparators provide a plurality of outputs in accordance with the comparisons. A logic circuit processes the comparison signals to provide sampling pulses. Switches receiving the amplified signals from the amplifying channel are controlled by the sampling pulses to sample the amplified signals to provide the analog output in accordance with the comparison signals. An analog-to-digital converter network receives the gain signal and the analog output and provides digital signals, some of which correspond to the gain signal while the remaining digital signals correspond to the plurality and magnitude of the analog output.

#The objects and advantages of the invention will appear more fully hereinafter, from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein several embodiments are illustrated by way of example. It is to be expressly understood, however, that the drawings are for illustrative purposes only and are not to be construed as defining the limits of the invention.

#FIG. 1 is a simplified block diagram of a seismic recording system constructed in accordance with one embodiment of the present invention.

#FIG. 2 is a simplified block diagram of a level comparator and a rate comparator which may be used with the system shown in FIG. 1 to provide another embodiment of the present invention.

#FIG. 3 is a simplified block diagram of a seismic recording system constructed in accordance with yet another embodiment of the present invention.

#In FIG. 1 there is shown a seismic signal processing and recording system, including a plurality of geophones, G1, G2 G.sub.n indicating the presence of a plurality of such acoustic-to-electric transducer devices as determined by the particular practice in the art, for example 12 or 24 or some other number thereof. Each of these geophones may in actuality comprise a group or cluster or a plurality of individual geophone instruments, with the respective output couple together provide a common geophone signal.

#In FIG. 1, the respective geophones G.sub.1, G.sub.2 and G.sub.n are shown coupled to the input portions of respective signal channels identified as channels 1, 2 and n respectively. Channels 1 through n are substantially identical, so that a description of Channel 1 is also applicable to any other channel. Three channels are shown in the illustrated embodiment; it is to be understood that Channel n is represented by one or more of such channels and that, in most cases, seismic signal process systems of the type described, comprise 12, 24 or larger number of channels.

#Channel 1 comprises a plurality of amplifier stages, A and B.sub.1 through B.sub.4 directly coupled, e.g. DC coupled, to one another in cascade circuit relationship, with coupling networks C.sub.1 through C.sub.4. A feedback circuit, including the circuit elements within the dashed box identified as O is provided from the output of the last cascade stage B.sub.4 to the input of the first cascade stage B.sub.1 and the feedback circuit O includes an active filter N having a high frequency roll off characteristic and characteristic gain of at least unity. The N portion of the feedback circuit O is a network of resistors and capacitors, the values of which may be selected to provide the desired frequency characteristic of feedback circuit O. An active stage comprising an operational amplifier M, provided for in the aforementioned feedback loop feedback circuit O, should have a gain of at least unity and for the present embodiment has a positive gain of unity. It is to be understood that a negative gain of at least minus one may be chosen, in which event it will be necessary to make an appropriate change in the manner of supplying feedback to the input of the cascade network in order to assure injection of the feedback in proper phase relationship with the input signal.