- Title Pages
- Preface
- Introduction
- Chapter 1 Better accuracy from simple pendulums
- Chapter 2 A short history of temperature compensation
- Chapter 3 Scaling the size of a pendulum
- Chapter 4 Finding a pendulum’s axis of rotation
- Chapter 5 Does a pendulum’s axis of rotation shift with amplitude?
- Chapter 6 Some practical properties of quartz
- Chapter 7 Putting Q in perspective
- Chapter 8 The Allan variance and the rms time error
- Chapter 9 Transient temperature effects in a pendulum
- Chapter 10 Transient response of a pendulum to temperature change
- Chapter 11 Dimensional stability of pendulum materials
- Chapter 12 Variations on a Riefler bob shape
- Chapter 13 Bob shape
- Chapter 14 Rate adjustment mechanisms
- Chapter 15 Spring suspensions for accurate pendulums
- Chapter 16 James’ suspension spring equations
- Chapter 17 Barometric compensation with a crossed spring suspension?
- Chapter 18 Solid one-piece suspension springs
- Chapter 19 Stable connections to a pendulum’s suspension spring
- Chapter 20 Stability of suspension spring materials
- Chapter 21 Pendulum rod materials
- Chapter 22 The heat treatment of invar
- Chapter 23 The instability of invar
- Chapter 24 Position sensitivity along the pendulum rod
- Chapter 25 Fasteners for quartz pendulum rods
- Chapter 26 Effect of the pendulum rod on Q
- Chapter 27 Correcting the pendulum’s air pressure error
- Chapter 28 Pendulum air movement: A failed experiment
- Chapter 29 Pendulum air movement: A second try
- Chapter 30 Time error due to air pressure variations
- Chapter 31 Effect of the clock case walls on a pendulum
- Chapter 32 An electronically driven pendulum
- Chapter 33 Sinusoidal drive of a pendulum
- Chapter 34 Photoelectronics for pendulums
- Chapter 35 Check your clock against WWV
- Chapter 36 Electronic correction for air pressure variations
- Conversion Table
- Index
Correcting the pendulum’s air pressure error
Correcting the pendulum’s air pressure error
- Chapter:
- (p.185) Chapter 27 Correcting the pendulum’s air pressure error
- Source:
- Accurate Clock Pendulums
- Author(s):
Robert James Matthys
- Publisher:
- Oxford University Press
This chapter describes how to calculate and remove the air pressure error from a clock's time error versus time chart. Depending on geographic location and the density of the pendulum materials, air pressure variations can cause roughly 2-18 seconds of error in a clock in a year's time interval. This is because the pendulum ‘floats’ in a sea of air, and variations in the air pressure make the pendulum slow down or speed up. In this chapter, the pressure error itself is described first, followed by an actual clock data run to show how the pressure error is calculated and then removed from a clock's time error versus time curve. Correcting for the pressure error corrects the clock's time to a constant average pressure at the clock site. The error is the product of the pressure difference times time. More specifically, it is the integral of the pressure difference with respect to time.
Keywords: pendulum, air pressure error, time, time error, air pressure
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- Title Pages
- Preface
- Introduction
- Chapter 1 Better accuracy from simple pendulums
- Chapter 2 A short history of temperature compensation
- Chapter 3 Scaling the size of a pendulum
- Chapter 4 Finding a pendulum’s axis of rotation
- Chapter 5 Does a pendulum’s axis of rotation shift with amplitude?
- Chapter 6 Some practical properties of quartz
- Chapter 7 Putting Q in perspective
- Chapter 8 The Allan variance and the rms time error
- Chapter 9 Transient temperature effects in a pendulum
- Chapter 10 Transient response of a pendulum to temperature change
- Chapter 11 Dimensional stability of pendulum materials
- Chapter 12 Variations on a Riefler bob shape
- Chapter 13 Bob shape
- Chapter 14 Rate adjustment mechanisms
- Chapter 15 Spring suspensions for accurate pendulums
- Chapter 16 James’ suspension spring equations
- Chapter 17 Barometric compensation with a crossed spring suspension?
- Chapter 18 Solid one-piece suspension springs
- Chapter 19 Stable connections to a pendulum’s suspension spring
- Chapter 20 Stability of suspension spring materials
- Chapter 21 Pendulum rod materials
- Chapter 22 The heat treatment of invar
- Chapter 23 The instability of invar
- Chapter 24 Position sensitivity along the pendulum rod
- Chapter 25 Fasteners for quartz pendulum rods
- Chapter 26 Effect of the pendulum rod on Q
- Chapter 27 Correcting the pendulum’s air pressure error
- Chapter 28 Pendulum air movement: A failed experiment
- Chapter 29 Pendulum air movement: A second try
- Chapter 30 Time error due to air pressure variations
- Chapter 31 Effect of the clock case walls on a pendulum
- Chapter 32 An electronically driven pendulum
- Chapter 33 Sinusoidal drive of a pendulum
- Chapter 34 Photoelectronics for pendulums
- Chapter 35 Check your clock against WWV
- Chapter 36 Electronic correction for air pressure variations
- Conversion Table
- Index