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Measurement of Time
Measurement of Time M.Y. ANAND, B.A. KAGALI* Department of Physics, Bangalore University, Bangalore 560056 *email: [email protected] ABSTRACT Time was historically measured using the periodic motions of the sun and stars. Various types of sun clocks were devised in Egypt, Greece and Europe. Different types of water clocks were assembled with ever greater accuracy. Only in the seventeenth century did the mechanical clock with pendulums and springs appeared. Accurate quartz clocks and atomic clocks were developed in the first half of the twentieth century. Now we have clocks that have better than microsecond accuracy. This article gives a brief account of all these topics. Keywords: Sun clocks, Water clocks, Mechanical clocks, Quartz clocks, Atomic clocks, World Time, Indian Standard time We all know intuitively what time is. It can be civilizations relied upon the apparent motion of roughly equated with change or motions. From these bodies through the sky to determine the very beginning man has been interested in seasons, months, and years. understanding and measuring time. More We know little about the details of recently, he has been looking for ways to limit timekeeping in prehistoric eras, but we find the “damaging” effects of time and going that in every culture, some people were backward in time! preoccupied with measuring and recording the Celestial bodies—the Sun, Moon, planets, passage of time. Ice-age hunters in Europe over and stars—have provided us a reference for 20,000 years ago scratched lines and gouged measuring the passage of time. Ancient holes in sticks and bones, possibly counting the Physics Education • January − March 2007 277 days between phases of the moon. -
What Time Is It?
The Astronomical League A Federation of Astronomical Societies Astro Note E3 – What Time Is It? Introduction – There are many methods used to keep time, each having its own special use and advantage. Until recently, when atomic clocks became available, time was reckoned by the Earth's motions: one rotation on its axis was a "day" and one revolution about the Sun was a "year." An hour was one twenty-fourth of a day, and so on. It was convenient to use the position of the Sun in the sky to measure the various intervals. Apparent Time This is the time kept by a sundial. It is a direct measure of the Sun's position in the sky relative to the position of the observer. Since it is dependent on the observer's location, it is also a local time. Being measured according to the true solar position, it is subject to all the irregularities of the Earth's motion. The reference time is 12:00 noon when the true Sun is on the observer's meridian. Mean Time Many of the irregularities in the Earth's motion are due to its elliptical orbit. In order to add some consistency to the measure of time, we use the concept of mean time. Mean time uses the position of a fictitious "mean Sun" which moves smoothly and uniformly across the sky and is insensitive to the irregularities of the Earth’s motion. A mean solar day is 24 hours long. The "Equation of Time," tabulated in almanacs and represented on maps by the analemma, provides the correction between mean and apparent time to allow for the eccentricity of the Earth's orbit. -
Illustrating Time's Shadow Supplements
Illustrating Time's Shadow Supplements Supplemental Shadows This book addresses small indoor sundials of wood, glass, and PVC, as well as outside garden dials of glass, clay, tile, and common building materials. Less common dial features such as the inclined decliner and calendar or declination curves, are covered, as well as the astrolabe, other altitude dials and azimuth time keepers. This book uses empirical, geometric, trigonometric, CAD (computer aided design) both 2d and 3d, spreadsheet, procedural programming, tabular methods, and other techniques. Tables are provided. Simon Wheaton-Smith 1 ILLUSTRATING TIME’S SHADOW The Supplements Supplemental Shadows enhances both the book Illustrating Time’s Shadow as well as its associated Appendices by Simon Wheaton-Smith ISBN 978-0-9960026-1-5 Library of Congress Control Number: 2014904840 Simon Wheaton-Smith www.illustratingshadows.com (c) 2004-2018 Simon Wheaton-Smith All rights reserved. June 12, 2018 2 THE ILLUSTRATING SHADOWS COLLECTION Illustrating Shadows provides several books or booklets:- Simple Shadows Build a horizontal dial for your location. Appropriate theory. Cubic Shadows Introducing a cube dial for your location. Appropriate theory. Cutting Shadows Paper cutouts for you to make sundials with. Illustrating Times Shadow the big book Illustrating Times Shadow ~ Some 400 pages covering almost every aspect of dialing. Includes a short appendix. Appendices Illustrating Times Shadow ~ The Appendices ~ Some 180 pages of optional detailed appendix material. Supplement Supplemental Shadows ~ Material in the form of a series of articles, covers more on the kinds of time, declination confusion, other proofs for the vertical decliner, Saxon, scratch, and mass dials, Islamic prayer times (asr), dial furniture, and so on! Programming Shadows A book discussing many programming languages, their systems and how to get them, many being free, and techniques for graphical depictions. -
Mini Quartz Clock Movements
Mini Quartz Clock Movements • 10 Year Warranty • Step Second Hand • Dimensions: 2-1/8"W x 2-1/8"H x 5/8"D • Runs on 1 "AA" Size Battery • American "I" Shaft - Diameter 5/16" • Free Set Of Hands and • Front Loading Hanger Mounting Hardware With • Accurate Within 2 Minutes A Year Each Clock Movement • Fits 3" Diameter Hole • Made in USA 1. Drill a 3/8" hole through the material you are working with and insert the movement. 2. Slide brass washer over shaft. 3. Attach dial mounting hex nut. 4. Gently press hour hand onto shaft at 12:00 position. 5. Place minute hand over shaft at 12:00 position. 6. Gently screw minute nut in place. 7. Press on second hand at 12:00 position. 8. Screw on cap nut if no second hand is used. Mini Movements Shaft Length Selecting the Proper Shaft Length Dials B A P r i c e E a c h P e r P k g O f Proper shaft length is important to ensure Stock# up to Thread Total 1 3 10 50 100 sufficient clearance when going through your dial Q-11 1/8" thick 3/16" 17/32" 4.95 4.23 4.45 3.80 4.25 3.63 3.95 3.38 3.75 3.21 board and when using a glass front on your clock. Q-12 1/4" thick 5/16" 5/8" 4.95 4.23 4.45 3.80 4.25 3.63 3.95 3.38 3.75 3.21 Overall Length (A) is measured from the tip of Q-13 3/8" thick 7/16" 3/4" 4.95 4.See23 4.4 website5 3.80 4.25 3for.63 3current.95 3.38 3.75 3.21 the hand shaft to the movement cast. -
Analog Clock Headway Movement FAQS
ANALOG CLOCK HEADWAY MOVEMENT FAQS The links below will work in most PDF viewers and link to the topic area by clicking the link. We recommend Adobe Reader version 10 or greater available at: http://get.adobe.com/reader CONTENTS Analog Clock Headway Movement FAQS .................................................................... 1 Batteries ............................................................................................................................. 2 Atomic Clock Factory Restart ...................................................................................... 2 Supported Time Zones .................................................................................................. 2 Time is Incorrect ............................................................................................................. 2 Clock is incorrect by Hours but minutes are correct .......................................... 3 Daylight Saving Time ..................................................................................................... 3 Manually Set Time ........................................................................................................... 3 How long will the battery last? .................................................................................. 3 Can I shut off the WWVB signal? .............................................................................. 3 Is there a booster antenna to receive the WWVB signal in a difficult location? ............................................................................................................................ -
77A71 Quartz Clock Movement Instructions
77A71 07/28/94 Quartz Clock Movement Instructions Product #3722X, 3723X The 3622X and 3723X quartz battery movements will operate The 3723X movement has a start-stop switch on the rear of the approximately 12 months on a fresh “C” alkaline battery. Insert the case. Both movements feature a hand set knob on the rear of the battery with positive end to your left as movement is held upright case. Telephone time recordings are generally adequate for setting looking from the rear. the time. The 3722X and 3723X movements should keep time to +/- To mount the movement, insert the handshaft through the center 10 seconds per month. hole in your dial and fasten with the brass nut and brass washer. Be sure to use a fresh battery when you install your clock. If you are The hanger and one or more shims (rubber washer) may be neces- not sure, have it tested on a battery testing device. Do not attempt sary between the movement and the dial to control the distance that to disassemble the movement case for any kind of service. the handshaft protrudes through the dial. (See Diagram A) The adjustable pendulum on the 3722X adjustable pendulum Press the hour hand onto its shaft, making sure it does not rub movement has no bearing on the time keeping of the movement against the dial. The minute hand fits onto the threaded “I” shaft itself and can be adjusted by “breaking” the brass rod at the scored and is held by a small nut. The second hand (optional) may now be lines and then replacing the brass bob. -
NIST Time and Frequency Services (NIST Special Publication 432)
Time & Freq Sp Publication A 2/13/02 5:24 PM Page 1 NIST Special Publication 432, 2002 Edition NIST Time and Frequency Services Michael A. Lombardi Time & Freq Sp Publication A 2/13/02 5:24 PM Page 2 Time & Freq Sp Publication A 4/22/03 1:32 PM Page 3 NIST Special Publication 432 (Minor text revisions made in April 2003) NIST Time and Frequency Services Michael A. Lombardi Time and Frequency Division Physics Laboratory (Supersedes NIST Special Publication 432, dated June 1991) January 2002 U.S. DEPARTMENT OF COMMERCE Donald L. Evans, Secretary TECHNOLOGY ADMINISTRATION Phillip J. Bond, Under Secretary for Technology NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY Arden L. Bement, Jr., Director Time & Freq Sp Publication A 2/13/02 5:24 PM Page 4 Certain commercial entities, equipment, or materials may be identified in this document in order to describe an experimental procedure or concept adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the entities, materials, or equipment are necessarily the best available for the purpose. NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY SPECIAL PUBLICATION 432 (SUPERSEDES NIST SPECIAL PUBLICATION 432, DATED JUNE 1991) NATL. INST.STAND.TECHNOL. SPEC. PUBL. 432, 76 PAGES (JANUARY 2002) CODEN: NSPUE2 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 2002 For sale by the Superintendent of Documents, U.S. Government Printing Office Website: bookstore.gpo.gov Phone: (202) 512-1800 Fax: (202) -
Overview of the National Measurement System's Time and Frequency Programme
Overview of the National Measurement System’s Time and Frequency Programme Dale Henderson Projects to support the maintenance of UTC “The Maintenance and Development of UTC(NPL)” The objectives of this project are to support the operation and development of the international civil time scale, Coordinated Universal Time (UTC), in partnership with the BIPM and the national time standards laboratories from other countries around the world; and to provide a reference time standard for the UK that is traceable to the international civil time scale, Coordinated Universal Time (UTC). Its main deliverable is UTC(NPL), a continuously operating national time scale that is traceable to UTC, with the uncertainty in the UTC-UTC(NPL) offsets published in the BIPM Circular T to be established with an uncertainty of ± 5 ns (1s) or better. UTC and TAI UT-1 is based on siderial time as monitored by the IERS TAI maintained by BIPM under the Metre Convention TAI is an Atomic time, step interval 1 SI second on the Geoid UTC is “owned” by ITU (recommendation TF 460) and has the rate of TAI but is stepped to follow UT-1 International time-keeping since 1972 40 time laboratories around the world with more than 200 atomic clocks keep world time Laboratory time standards compared using satellite links Global standards – International Atomic Time (TAI) and Coordinated Universal Time (UTC) – are computed by the BIPM each calendar month System calibrated by ~8 primary frequency standards 150 100 50 USNO PTB 0 NPL 50800 51300 51800 IEN -50 UTC - UTC(k) [ns] -100 -150 -
Time and Frequency Division Report
Time and Frequency Division Goal The broad mission of the Time and Frequency Division is to provide official U.S. time and related quantities to support a wide range of uses in industry, national infrastructure, research, and among the general public. DIVISION STRATEGY The division’s research and metrology ac- tivities comprise three vertically integrated components, each of which constitutes a strategic element: 1. Official time: Accurate and precise realization of official U.S. time (UTC) and frequency. 2. Dissemination: A wide range of mea- surement services to efficiently and effectively distribute U.S. time and frequency and related quantities – pri- marily through free broadcast services available to any user 24/7/365. 3. Research: Research and technolo- gy development to improve time and frequency standards and dissemination. Part of this research includes high-impact programs in areas such as quantum information processing, atom-based sensors, and laser development and applications, which evolved directly from research to make better frequency standards (atomic clocks). Overview These three components – official time, dissemination, and research – are closely integrated. For example, all Division dissemination services tie directly to the Division’s realization of official time (UTC), and much of the Division’s research is enabled by the continual availability of precision UTC. Our modern technology and economy depend critically on the broad availability of precision timing, frequency, and synchronization. NIST realization and dissemination of time and frequency – continually improved by NIST research and development – is a crucial part of a series of informal national timing infrastructures that enable such essential technologies as: • Telecommunications and computer networks • Utility distribution • GPS, widely available in every cell phone and smartphone as well as GPS receivers • Electronic financial transactions 1 • National security and intelligence applications • Research Strategic Goal: Official Time Intended Outcome and Background U.S. -
Kintaro Hattori in 1881 Founded the Company That Was to Become Seiko
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Representation of Date and Time Data Standard
REPRESENTATION OF DATE AND TIME DATA STANDARD Standard No.: EX000013.1 January 6, 2006 This standard has been produced through the Environmental Data Standards Council (EDSC). Representation of Date and Time Data Standard Std No.: EX000013.1 Foreword The Environmental Data Standards Council (EDSC) identifies, prioritizes and pursues the creation of data standards for those areas where information exchange standards will provide the most value in achieving environmental results. The Council involves Tribes and Tribal Nations, state and federal agencies in the development of the standards and then provides the draft materials for general review. Business groups, non-governmental organizations, and other interested parties may then provide input and comment for Council consideration and standard finalization. Standards are available at http://www.epa.gov/datastandards 1.0 INTRODUCTION This is a format standard which indicates how one displays a particular day within a Gregorian calendar month and specifies an instance of time in the day. Time is expressed in Coordinated Universal Time (UTC). UTC is the official time scale, maintained by the Bureau International des Poids et Mesures (BIPM), and the International Earth Rotation Service (IERS). Examples of the formats follow: a. Date only format When the need is for an expression only of a calendar date, then the complete representation shall be a single numeric data element comprising eight digits, where [YYYY] represents a calendar year, [MM] the ordinal number of a calendar month within the calendar year, and [DD] the ordinal number of a day within the calendar month. Extended format: YYYY-MM-DD EXAMPLE 1985-04-12 b. -
Best Practices for Leap Second Event Occurring on 30 June 2015
26 May 2015 Best Practices for Leap Second Event Occurring on 30 June 2015 Sponsored by the National Cybersecurity and Communications Integration Center in coordination with the United States Naval Observatory, National Institute of Standards and Technology, the USCG Navigation Center, and the National Coordination Office for Space-Based Positioning, Navigation and Timing. This product is intended to assist federal, state, local, and private sector organizations with preparations for the 30-June 2015 Leap Second event. Entities using precision time should be mindful that no leap second adjustment has occurred on a non- holiday weekday in the past decade. Of the three leap seconds implemented since 2000, two have been scheduled on 31 December and the most recent was on Sunday, 1 July 2012. Please report operational challenges you experience to the following organizations: GPS -- United States Coast Guard Navigation Center (NAVCEN), via the NAVCEN Website, http://www.navcen.uscg.gov/ under "Report a GPS Problem" Network Timing Protocols (NTP) -- Michael Lombardi at NIST, Boulder, Colorado at 303-497- 3212, or [email protected]. ============================================= 1. Leap Second Introduction The Coordinated Universal Time (UTC) time standard, based on atomic clocks, is widely used for international timekeeping and as the reference for time in most countries. UTC is the basis of legal time for most of the world. UTC must be adjusted at irregular intervals to maintain its correlation to mean solar time due to irregularities in the Earth’s rotation. These adjustments, called leap seconds, are pre-determined. The next leap second will occur on 30 June 2015 at 23:59:59 UTC.