Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Gravimeter shopping experience:

1. Compare - without doubt the biggest advantage that the Gravimeter offers shoppers today is the ability to compare thousands of Gravimeter at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Gravimeter? Wrong! If the Gravimeter is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Gravimeter then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Gravimeter? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Gravimeter and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Gravimeter wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Gravimeter then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Gravimeter site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Gravimeter, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Gravimeter, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

A gravimeter or gravitometer, is an instrument used in gravimetry for measuring the local gravitational field. A gravimeter is a type of accelerometer, except that gravimeters are susceptible to all vibrations including noise, that cause oscillatory accelerations. This is counteracted by integral vibration isolation and signal processing. Though the essential principle of design is the same as in accelerometers, gravimeters are typically designed much more sensitive than accelerometers in order to measure very tiny changes within the Earth's gravity, of 1 g-force). In contrast, accelerometers are often designed to measure 1000 g or more, and many perform multi-axial measurements. The constraints on temporal resolution are usually less for gravimeters, so that resolution can be increased by processing the output with a longer "time constant".

Basically, there are two kinds of gravimeters: relative and absolute.

Most common relative gravimeters are spring (device) based. They are used in gravity surveys over large areas for establishing the figure of the geoid over those areas. A spring-based relative gravimeter is basically a weight on a spring, and by measuring the amount by which the weight stretches the spring, local gravity can be measured. However, the strength of the spring must be calibrated by placing the instrument in a location with a known gravitational acceleration. Most accurate relative gravimeters are superconducting gravimeters, and these are sensitive to one thousandth of one billionth of the Earth surface gravity. Twenty-some superconducting gravimeters are used worldwide for studying Earth tides, rotation, interior, and ocean and atmospheric loading, as well as for verifying the Newtonian constant of gravitation.Omerbashich M., Earth-Model Discrimination Method, pp.129, Ph.D. Dissertation, University of New Brunswick, Canada (2003). Other uses of gravimeters in physics include the detection of possible changes in the gravitational field in various anti-gravity experiments.

Absolute gravimeters, which nowadays are made compact so they too can be used in the field, are based directly on measuring the acceleration of free fall (for example, of a reflecting prism_(optics) in a vacuum tube). They are used for establishing the vertical control network. An absolute gravimeter is used to calibrate relative gravimeters, and it operates by letting a mass free fall in vacuum and measuring its rate of acceleration. The mass includes a retroreflector and terminates one arm of a Michelson interferometer. By counting and timing the interference fringes, the velocity of the mass can be measured. A more recent development is a "rise and fall" version that tosses the mass upward and measures both upward and downward motion. This allows cancellation of some measurement errors.

A high-grade, calibrated spring gravimeter such as the portable LaCoste-Romberg gravimeter can measure the Earth's gravitational field to within 1 gal (unit), or (0.1 nanometre/s²). Measurements of the surface gravity of the Earth are part of geophysics analysis.

References

A gravimeter or gravitometer, is an instrument used in gravimetry for measuring the local gravitational field. A gravimeter is a type of accelerometer, except that gravimeters are susceptible to all vibrations including noise, that cause oscillatory accelerations. This is counteracted by integral vibration isolation and signal processing. Though the essential principle of design is the same as in accelerometers, gravimeters are typically designed much more sensitive than accelerometers in order to measure very tiny changes within the Earth's gravity, of 1 g-force). In contrast, accelerometers are often designed to measure 1000 g or more, and many perform multi-axial measurements. The constraints on temporal resolution are usually less for gravimeters, so that resolution can be increased by processing the output with a longer "time constant".

Basically, there are two kinds of gravimeters: relative and absolute.

Most common relative gravimeters are spring (device) based. They are used in gravity surveys over large areas for establishing the figure of the geoid over those areas. A spring-based relative gravimeter is basically a weight on a spring, and by measuring the amount by which the weight stretches the spring, local gravity can be measured. However, the strength of the spring must be calibrated by placing the instrument in a location with a known gravitational acceleration. Most accurate relative gravimeters are superconducting gravimeters, and these are sensitive to one thousandth of one billionth of the Earth surface gravity. Twenty-some superconducting gravimeters are used worldwide for studying Earth tides, rotation, interior, and ocean and atmospheric loading, as well as for verifying the Newtonian constant of gravitation.Omerbashich M., Earth-Model Discrimination Method, pp.129, Ph.D. Dissertation, University of New Brunswick, Canada (2003). Other uses of gravimeters in physics include the detection of possible changes in the gravitational field in various anti-gravity experiments.

Absolute gravimeters, which nowadays are made compact so they too can be used in the field, are based directly on measuring the acceleration of free fall (for example, of a reflecting prism_(optics) in a vacuum tube). They are used for establishing the vertical control network. An absolute gravimeter is used to calibrate relative gravimeters, and it operates by letting a mass free fall in vacuum and measuring its rate of acceleration. The mass includes a retroreflector and terminates one arm of a Michelson interferometer. By counting and timing the interference fringes, the velocity of the mass can be measured. A more recent development is a "rise and fall" version that tosses the mass upward and measures both upward and downward motion. This allows cancellation of some measurement errors.

A high-grade, calibrated spring gravimeter such as the portable LaCoste-Romberg gravimeter can measure the Earth's gravitational field to within 1 gal (unit), or (0.1 nanometre/s²). Measurements of the surface gravity of the Earth are part of geophysics analysis.

References