Horology: time measuring systems or devices – Time interval – Electrical or electromechanical
Reexamination Certificate
1997-06-13
2001-12-04
Miska, Vit (Department: 2859)
Horology: time measuring systems or devices
Time interval
Electrical or electromechanical
C368S118000, C331S111000, C331S143000
Reexamination Certificate
active
06327223
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the measurement of time and more particularly to electronic time measurement systems employing a timer of sub-pico second (10
−12
sec. ) resolution and accuracy. A time of day (real time ) clock is derived from the timer.
PRIOR ART AND INFORMATION DISCLOSURE
Various schemes have been devised for electronic timers. Such timers are better described as “time interval meters”. In most schemes, the time interval meters have limited range, like a thousand seconds. Conversely, time-of-day clocks rarely have more than a millisecond timing capability. The present limitations of timers and clocks, their shortcomings and deficiencies still exist in the technology.
Specifically, existing timers and clocks simply do not provide approaches for integrating timers and clocks in the sub-picosecond domain. Examples of existing technology are discussed below.
U.S. Pat. No. 3,983,481 to Nutt et al discloses a digital “intervalometer providing a resolution finer than one clock period by charging a single capacitor both during the interval between a start signal and a subsequent clock pulse and also during the interval between a clock pulse subsequent to a stop signal and a delayed stop signal. The analog voltage to which the capacitor is charged is converted to a digital value and then combined with a clock count accumulated between the stop and start signals.
U.S. Pat. No. 4,505,155 discloses a device having a constant current source which charges a reference capacitor by a high speed analog switch when a first event occurs and turning the current off by a second high speed switch when a second event occurs. The voltage produced by the charge on the capacitor is proportional to the time between events.
U.S. Pat. No. 4,162,443 to Brearley et al discloses frequency measurement by counting the number of pulses and the fractional value of an incomplete cycle occurring during a fixed sampling period. The length of the incomplete cycle is measured using a clock pulse having a base frequency multiplied by an integral factor based on the number of complete pulses occurring during the sampling period.
U.S. Pat. No. 4,736,351 to Oliver discloses a microprocessor controlling a programable oscillator directing it to produce pulses of variable width frequency.
U.S. Pat. No. 4,870,629 to Swerlein et al discloses a method of calibration for a voltage to time convertor in order to increment delays by a fraction of a clock cycle.
U.S. Pat. No. 4,772,843 to Asaka et al discloses measurement of a first interpolation pulse extending between a start time and a clock signal and a second interpolation pulse extending from a stop time and a stop interpolation pulse.
U.S. Pat. No. 3,790,890 to Doittau et al discloses a capacitor which is charged during a first time interval which depends on the time interval to be measured and discharged during a later time interval that is multiple of the first time interval and can therefore be measured more accurately than the first time interval.
U.S. Pat. No. 3,790,828 to Klein discloses a system utilizing a fast ramp voltage and a slow ramp voltage starting in unison with the start signal. When the stop signal is received, the first ramp voltage is stopped and the interval of time (clock pulses) emitted until the second ramp voltage is reached is proportional to time between the stop and start signals.
U.S. Pat. No. 4,301,360 to Blair discloses a timing circuit operable at a fast predetermined rate over the time between a stop and start event and operable at slow predetermined rate scaled to the first predetermined rate, between the stop event and the upper limit of a timing window.
U.S. Pat. No. 4,764,694 to Winroth discloses time expansion circuits to expand the initial and final portions of the duration of an event so as to measure more precisely those time segments that are typically not integral numbers of clock periods in length.
U.S. Pat. No. 4,79,798 to Hayashi discloses conversion of the period between stop and start pulses of input pulses into a voltage in which fractional times between pulses are converted by two fractional time to voltage converters, alternately with one another, into voltage signals and the voltage signals alternately applied by a change-over switch to a subtractor taking the difference between the successive fractional times, to create a difference signal. The difference signal is added to the analog signal of the number of clock pulses between the stop and start signals.
U.S. Pat. No. 4,514,835 to Bottigheimer et al discloses a device for measuring time intervals between successive events including a clock pulse generator coupled via a gating circuit to a counter. The output of the counter is connected to a shift register for screening out and storing momentary events of the counter.
U.S. Pat. No. 5,001,683 to Fukumoto et al discloses an inter time difference measuring circuit which expands the time difference between a first pulse and a second pulse by a given multiplication factor and measures the expanded time difference thereby realizing a higher measuring resolution.
U.S. Pat. No. 4,164,648 to Chu discloses measurement of a time interval between a stop and start event by activating a start oscillator in response to the start event and activating a stop oscillator in response to a stop event. The number of cycles of each respective oscillator signal which occurs between activation of each oscillator and the coincidence of the respective oscillator signals is used to determine the time between stop and start events.
U.S. Pat. No. 4,620,788 to Giger discloses apparatus for measuring time delay between start and stop pulse signals comprising a coarse measuring counter that counts the output of a reference oscillator while a fine measurement interpolator determines the residual time between the start pulse and the first oscillator pulse and the stop pulse to the next oscillator pulse.
U.S. Pat. No. 4,772,843 to Asaka et al discloses two time-to-converter which are dedicated to time a start pulse and a stop pulse respectively. The invention is a start pulse and a stop pulse spaced in close proximity in time that can be individually measured without conflict.
U.S. Pat. No. 5,200,933 to Thorton et al discloses a high resolution data acquisition system that incorporates an integrating capacitor whose charging time is proportional to a pulse train, where the output of the capacitor is applied to an A-D converter and expressed into time by processing.
Additional references regarding the present art are to be found in:
W. Weber et al, “Time-to-Pulse Height Converter Measurement of Millimicrosecond Time Intervals”, The Review of Scientific Measurements Vol. 27, No. 3 (March, 1956)
J/Kalisz et al, “Error Analysis and Design of the Nutt Time-Interval Digitiser with Picosecond Resolution” J. Phys. E. Sci. Instrum 20: 1330 (1987)
Existing timers and clocks that do have 9
+
accuracy are large laboratory instruments requiring highly skilled people to calibrate them. As a result, the available equipment is quite expensive.
Because the equipment is not easily transportable, the applied engineering and chemistry field usually do not have daily access to such sophisticated equipment.
Additionally, the calibration of these timer and clock systems must be rigorously monitored. In many instances, calibration of the equipment must be performed in special facilities.
These are only a few of the problems which have not been adequately resolved by existing technology.
SUMMARY
It is an object of this invention to provide solutions and advantages which overcome many of these problems.
This invention is directed toward a system to measure time to 10
−12
seconds. The timer may be integrated into a real time of day clock.
A timing system of this invention includes:
a calibrated timer unit (CTU) whose unit of time base (pulse length or time between start stop, etc.) is the shortest unit of time of the timer system. This shortest unit of time is referred to herein as a “segment” so that the output of the CTU is o
Miska Vit
Zimmerman C. Michael
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