Method and apparatus for measuring a local acceleration of gravity

Patent metadata

Field	Value
Publication number	US-10012757-B2
Application number	US-201615003460-A
Country	US
Kind code	B2
Filing date	Jan 21, 2016
Priority date	Jan 21, 2016
Publication date	Jul 3, 2018
Grant date	Jul 3, 2018

Abstract

An apparatus and method for measuring a local acceleration of gravity includes releasing a ferrous rod having a regular alternating pattern of reflective and non-reflective portions on a surface thereof from an electromagnetic holder so that the rod falls with a substantially vertical acceleration and substantially no angular velocity about a center of mass of the rod. The falling rod is illuminated with a light emitting diode (LED) configured to emit infrared (IR) light, and IR light emitted by the LED and reflected by the falling rod is detected with a photodiode. A two-state signal is generated corresponding to an illumination state of the photodiode by the reflected IR light. Times of transitions between the two states in the generated signal are calculated to determine kinematic data, and the kinematic data is fitted to a predetermined curve to calculate a local acceleration of gravity.

First claim

We claim:

1. An apparatus for measuring a local acceleration of gravity, the apparatus comprising:
a ferrous rod having a regular alternating pattern of reflective and non-reflective portions on a surface thereof;
an electromagnetic holder configured to releasably hold the ferrous rod;
an infrared (IR) transceiver including
a light emitting diode (LED) configured to emit IR light,
a photodiode configured to detect IR light emitted by the LED which is reflected back to the IR transceiver, and
an output circuit configured to output a two-state signal corresponding to an illumination state of the photodiode by the reflected IR light;

a power supply configured to the power the electromagnetic holder and the IR transceiver; and
circuitry configured to:
control a current from the power supply to the electromagnetic holder to the cause electromagnetic holder to release the rod,
cause the IR transceiver to emit IR light,
receive the signal from the IR transceiver,
calculate times of transitions between the two states in the received signal to determine kinematic data, and
calculate a local acceleration of gravity from a fit to the kinematic data.

2. The apparatus according to claim 1 , wherein the rod has a substantially cylindrical shape.

3. The apparatus according to claim 1 , wherein the alternating pattern is formed at regular intervals of 1 centimeter.

4. The apparatus according to claim 1 , where in the alternating pattern is formed by etching a surface of the rod.

5. The apparatus according to claim 1 , wherein the alternating pattern is formed by applying a black resin, epoxy, or paint to a surface of the ferrous rod.

6. The apparatus according to claim 5 , wherein transitions between the reflective portions and the non-reflective portions of the alternating pattern are blurred by varying a concentration of an IR absorber in the black resin, epoxy, or paint in a portion of the alternating pattern at the transition.

7. The apparatus according to claim 5 , wherein the surface of the rod is shaped in a pattern corresponding to the reflective portions and the non-reflective portions of the rod.

8. The apparatus according to claim 7 , wherein the surface of the rod is shaped in a concave pattern corresponding to the reflective portions and the non-reflective portions of the rod.

9. The apparatus according to claim 1 , wherein the alternating pattern is formed by printing a black and white pattern on paper and fixing the paper to the ferrous rod.

10. A method for measuring a local acceleration of gravity comprising:
releasing a ferrous object having a regular alternating pattern of reflective and non-reflective portions on a surface thereof from an electromagnetic holder so that the object falls with a substantially vertical acceleration and substantially no angular velocity about a center of mass of the object;
illuminating the falling object with a light emitting diode (LED) configured to emit infrared (IR) light;
detecting IR light emitted by the LED and reflected by the falling object with a photodiode configured to detect IR light emitted by the LED and reflected by the falling object;
generating a two-state signal based on the detecting, the two-state signal corresponding to an illumination state of the photodiode by the reflected IR light;
calculating times of transitions between the two states in the generated signal to determine kinematic data;
fitting the kinematic data to a predetermined curve; and
calculating a local acceleration of gravity from the fitting.

11. The method according to claim 10 , further comprising:
second releasing the ferrous object having the regular alternating pattern of reflective and non-reflective portions on the surface thereof from the electromagnetic holder so that the object falls with a substantially vertical acceleration and substantially no angular velocity about the center of mass of the object;
second illuminating the falling object with a light emitting diode (LED) configured to emit infrared (IR) light;
second detecting IR light emitted by the LED and reflected by the falling object with a photodiode configured to detect IR light emitted by the LED and reflected by the falling object;
second generating a two-state signal based on the detecting, the two-state signal corresponding to an illumination state of the photodiode by the reflected IR light; and
second calculating times of transitions between the two states in the generated signal to determine kinematic data,
wherein the releasing is a first releasing,
wherein the illuminating is a first illuminating,
wherein the detecting is a first detecting,
wherein the generating is a first generating,
wherein the calculating is a first calculating, and
wherein the fitting the kinematic data to the predetermined curve includes the kinematic data from the first calculating and the kinematic data from the second calculating.

12. A non-transitory computer-readable medium storing a program thereon for causing a computer to perform a method for measuring a local acceleration of gravity, the method comprising:
releasing a ferrous object having a regular alternating pattern of reflective and non-reflective portions on a surface thereof from an electromagnetic holder so that the object falls with a substantially vertical acceleration and substantially no angular velocity about a center of mass of the object;
illuminating the falling object with a light emitting diode (LED) configured to emit infrared (IR) light;
detecting IR light emitted by the LED and reflected by the falling object with a photodiode configured to detect IR light emitted by the LED and reflected by the falling object;
generating a two-state signal based on the detecting, the two-state signal corresponding to an illumination state of the photodiode by the reflected IR light;
calculating times of transitions between the two states in the generated signal to determine kinematic data;
fitting the kinematic data to a predetermined curve; and
calculating a local acceleration of gravity from the fitting.

Assignees

• Univ King Fahd Pet & Minerals

Inventors

• ABDELAZEM Sohaib
• Al-Basheer Watheq

Classifications

• G01V7/04

  Electric, photoelectric, or magnetic indicating or recording means · CPC title

• G01V7/14 Primary

  using free-fall time · CPC title