Seismic strong-motion recorder
First Claim
1. A digital recorder system for recording digital representations of portions of a continuously variable waveform which portions are of interest because they have amplitudes that exceed a preset threshold level, and for leaving unrecorded other non-interesting portions of the continuous waveform whose amplitudes fail to exceed said threshold level, the recorder comprising:
- (a) signal input means;
(b) periodic amplitude sampling means operative to sample the amplitude of the input signal waveform from said input means at uniformly spaced sampling intervals to produce sample point data;
(c) data processing means including a microprocessor and programmable read only memory (PROM) means operative to program the microprocessor to format said point data for subsequent recording, and the processing means further including recording timing means;
(d) a digital electronic pre-event buffer having an output and having an input connected to receive continuously all of the formatted point data, which is entered into it under control of the microprocessor, newly entered data displacing from said output of the buffer previously entered data;
(e) a digital electronic permanent memory having data recording capacity larger than the capacity of the pre-event buffer, the memory being operative to receive and permanently store point data;
(f) the processing means further including means for comparing with said threshold level with the input signal amplitude level represented by each data point entered at the input of the pre-event buffer, and the microprocessor then entering for storage in said permanent memory all point data which is displaced from the buffer output continuously for as long as said threshold level is exceeded at the input plus an interval of time determined by said timing means and commencing when the input amplitude level falls below said threshold level,(g) whereby a digital representation of the continuously variable waveform is permanently stored in the memory from a time beginning prior to its input amplitude exceeding said threshold level and extending through said timing interval after the input amplitude fails to exceed said threshold level.
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Accused Products
Abstract
A digital recorder and method for digitizing and recording seismic events, the recorder being capable of lengthy stand-by periods during which it records lesser events of little interest in a static buffer and then displaces these events with more recent events when the static buffer is full. The recorder is self powered and controlled by a microprocessor to transfer strong-motion signals representing important seismic events from the static buffer into a static memory which is kept alive by suitable back-up batteries and comprises a cartridge separable and retrievable from the recorder after a major seismic event. The information in the recorder also is accessible through a serial port for reading out to a central data processor. The seismic information is specially compressed and formatted to increase the amount of data recorded by eliminating data that is essentially redundant. The recorder comprises a package designed to protect the electronic circuitry and three orthogonally arranged seismometers in a sealed compartment, and to house the power supply including rechargeable batteries in an easily accessible vented compartment.
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Citations
17 Claims
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1. A digital recorder system for recording digital representations of portions of a continuously variable waveform which portions are of interest because they have amplitudes that exceed a preset threshold level, and for leaving unrecorded other non-interesting portions of the continuous waveform whose amplitudes fail to exceed said threshold level, the recorder comprising:
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(a) signal input means; (b) periodic amplitude sampling means operative to sample the amplitude of the input signal waveform from said input means at uniformly spaced sampling intervals to produce sample point data; (c) data processing means including a microprocessor and programmable read only memory (PROM) means operative to program the microprocessor to format said point data for subsequent recording, and the processing means further including recording timing means; (d) a digital electronic pre-event buffer having an output and having an input connected to receive continuously all of the formatted point data, which is entered into it under control of the microprocessor, newly entered data displacing from said output of the buffer previously entered data; (e) a digital electronic permanent memory having data recording capacity larger than the capacity of the pre-event buffer, the memory being operative to receive and permanently store point data; (f) the processing means further including means for comparing with said threshold level with the input signal amplitude level represented by each data point entered at the input of the pre-event buffer, and the microprocessor then entering for storage in said permanent memory all point data which is displaced from the buffer output continuously for as long as said threshold level is exceeded at the input plus an interval of time determined by said timing means and commencing when the input amplitude level falls below said threshold level, (g) whereby a digital representation of the continuously variable waveform is permanently stored in the memory from a time beginning prior to its input amplitude exceeding said threshold level and extending through said timing interval after the input amplitude fails to exceed said threshold level. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A seismic recorder system including seismometer means, digitizing means for digitizing data from the seismometer means, electronic temporary buffer means for receiving the digitized data, main electronic memory cartridge means, a power supply, and microprocessor means for controlling the recorder system, comprising:
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(a) upper and lower mating housing members defining upper and lower compartments; (b) the lower compartment mounting the seismometer means, the digitizing means, the electronic temporary buffer means, and the microprocessor means, and having a partition thereabove hermetically sealing the lower housing member; and (c) a vented upper housing member overlying the lower housing member and the partition, and the upper housing member containing the power supply and the main memory cartridge means removably mounted therein.
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13. The method of compressing and digitally recording varying continuous waveforms including the steps of:
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(a) sampling the amplitudes of a waveform at a series of sampling points which are spaced by uniform sampling intervals, and digitizing the amplitude at each point to provide spaced data points; (b) recording data representing a starting point; (c) establishing a linear slope approximating the slope of the waveform as it extends from said recorded starting point to a selected subsequent sampling point of the waveform, and establishing amplitude tolerances above and below the linear slope and offset therefrom by fixed predetermined plus-and-minus amplitude limits; (d) testing subsequent sampling points following said starting point to determine whether their amplitudes fall near said linear slope and within said tolerance limits, and recording data representing the last of said subsequent points on the waveform to fall within said limits, and recording a redundancy count number equal to the number of intervening sampling point intervals corresponding with unrecorded points falling within said limits and located between said recorded starting point and said last recorded point, and (e) repeating steps (c) and (d) using each last recorded point as a new starting point. - View Dependent Claims (14, 15, 16, 17)
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Specification