LaCoste-Romberg Gravity Meter No. DM-2


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Instruments \ Gravity \ Gravity Meters \

Name:	LaCoste-Romberg Gravity Meter No. DM-2	Date:	1960-present
Item Number:	87.05.02	Donor:	LaCoste-Romberg, Inc.
Type:	Model G Land Meter, Metal Zero-Length Spring type
Manufacturer:
	LaCoste-Romberg

Description:

Gravity meter No. DM-2 is a demonstration model of a G-Meter (Geodetic Model), with a galvo beam reading system. G-Meters operate using a metal zero-length spring and a lever-arm system. The lever-arm (beam) provides mechanical advantage and sensitivity to accurately measure the position of the mass at the end of the spring. This mass-balance system produces relative gravity measurements on the order of 1 part in one hundred million of the earth's field. This is equivalent to a bathroom scale that is capable of weighing yourself to determine how many buttons are on your shirt!

How does it work?

This particular model has two ways of reading the position of the mass -- through an optical system (the eyepiece near the center) and through an electronic system (the white gage at the top). The large white aluminum dial is rotated, turning a screw attached to the internal lever system, until the beam is moved to a reading line. The numbers on the dial and the odometer provide the gravity reading. The three large black knobs turn feet on the base of the meter in order to level the instrument.

G-Meters were the first land meters built with a world-wide 7,000 mGal range. This eliminated the need to reset the meter for different locations on the earth. With its 0.01 mGal accuracy and world-wide range, G-Meters are among the most popular of all the gravity meters ever produced. Since 1960, more than 1,100 have been manufactured and almost all are still in service today. These 8 lb. sensors have measured gravity in every country, have been to the top of every mountain range, collected data over every basin in every continent on the face of the globe. More than 25 million gravity stations have been surveyed with this type of instrument. It is estimated that once every 5 minutes a gravity station is measured with a G-Meter someplace in the world.

For more information, see the article: Gravity instruments: Past, present, future, The Leading Edge, January 1998, p. 100-112.

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