Dear Nadim,

The answer to your question can be found in the following text taken from a review article entitled "A Short Walk along the Gravimeters Path " published in 2012:

The terrestrial relative gravity world is dominated for several decades, since 1939, by LaCoste&Romberg gravity meters (Mod D and Mod G) and has witnessed in the last years the growth of Scintrex Autograv (CG3, CG5) (http://www.scintrexltd.com/gravity.html), Microg LaCoste (gPhone), http://www.microglacoste.com and ZLS (Burris), http://www.zlscorp.com. The long lasting superiority of LaCoste instrument was also due to the introduction of a capacitive transducer to monitor electronically the position of the beam in a much more impersonal way than the optical readout. It opened the way to the introduction of “feedback” electronics in order to keep always the beam of instruments at the same position (zero method). This technique was introduced first on the tidal LaCoste (ET meter) used for tidal registrations. The first attempt based on the use of a step motor to drive the micrometer was not very successful. Later an electrostatic restoring force has been used successfully. All instruments have nowadays electronic levels, electronic readout, and computer-controlled data acquisition. The reading sensitivity is of 1 10−9, the field repeatability around 5 10−9. The development of computer-controlled data acquisition and to certain extent also error compensation has certainly increased the instrumental reliability. As counter fact, the interaction between operator and gravity meter, which was inherent with the original instruments, has been lost.

Since the early days at the beginning of ‘80ties, absolute gravimetry has been subjected to continuous upgrade and developments, mainly due to the continuously increased R&D at Micro-g Solutions first and, since 2005, at Micro-g LaCoste. The original FG5 instrument, already an excellent instrument, has been followed by the FG5-X with a new dropping chamber and an extended free fall length of 36 cm within 260 ms, by FG-L, a simplified version of FG5 and A10, a smaller version of FG5 intended for field measurements. Declared accuracy of the order of 10−9 for FG5 and FG5-X and 10−8 for FG-L and A10. Reading the report of the Intercomparison Campaign of Absolute Gravimeters, held in Sevres, France at the BIPM laboratories in 2005, Jiang et al. 2011 [20] we clearly see that the absolute gravity world is dominated by free-fall-type instruments (FG5, A10, JILAg) with just few exceptions. One of these is the new instrument developed by the Italian Institute for Metrological Research-INRIM and indicated as IMGC-02, a memory of the original IMGC instrument. The instrument features a completely redesigned launching chamber, now automatic, a Mach-Zendher interferometer and computer-controlled data acquisition [21, 22] (Figure 7).

Figure 7: IMGC-02 absolute gravity meter.

The repeatability, of the order of 10−9 and the total uncertainty, 8 10−9, are similar to those of the free fall instruments. But what is very important to stress once again is the symmetry of the trajectory and its property of cancelling most, if not all, errors dependent from the frequency of the fringe signal.

Recently, J. E. Faller together with A. L. Vitoushkin 2005 [23], have developed a new absolute gravity meter which uses a cam to create the repeated necessary motions of hold, release, catch, and lift. By using a second cam that drives an auxiliary mass, it is possible to have the center of mass of the free fall system unchanged throughout the measurement cycle avoiding therefore any soil recoil effect. The instruments are very small, weighs less than 45 kg and have an accuracy comparable to that of the FG5.

The intercomparison campaigns are of high importance for the metrology of absolute gravimetry: they represent the best tool to identify and possibly correct for systematic errors and state the effective level of accuracy. Since 1981 the Bureau International des Poides et Mesures, Sevres, France has hosted eight campaigns (1981, 1985, 1989, 1994, 1997, 2001, 2005, 2009) while two campaigns (2003 and 2011) were held in Walferdange, Luxemburg at the European Center for Geodynamics and Seismology (ECGS). The increase in the numbers of instruments which participate in the campaigns is impressive [20] as well as the results of the last intercomparisons which indicate an agreement between the various instruments of about 2 10−9 (Figure8).

Figure 8: Impressive image of absolute gravimeters in “a raw” at Walferdange.

As far as Superconducting gravity meters is concerned, GWR Instruments, Inc. is the exclusive manufacturer of this kind of instruments. The levitation of a spherical test mass in an ultrastable magnetic field generated by persistent currents in two niobium coils that are superconducting below a temperature of 9.3 K replaces the mechanical spring. As a result, the ultrastable magnetic field, weak gradient, and operation at cryogenic temperatures eliminate the sources of noise and drift commonly found in mechanical spring gravity meters so that sensitivity of the instrument reaches the level of 10−12. GWR produces two types of SG: the GWR Observatory Superconducting Gravimeter and iGrav SG Meter-Simplified Superconducting Gravimeter for Portable Operation.

After 30 years of continuous development of gravity meters we now have at our disposal a powerful pool of high precision and high accuracy instruments to study our dynamic Earth. It is almost impossible to overview the high amount of scientific papers which report field of applications and results of gravity experiments. List of relevant papers on the use of superconducting gravimeters can be found athttp://www.gwrinstruments.com/published-papers.html and on the use of absolute gravity meters athttp://www.microglacoste.com/grav_bib.php.

For more details, please use the following link:

http://www.hindawi.com/journals/ijge/2012/687813/

Hoping this will be helpful,

Rafik

Dear Rafik,

Thank you indeed for your answer. This exactly what I am looking for. 

Nadim

Dear Nadim.

I think it is CG-5 Scintrex Autograv , Kanada.

Best Regards    Vagif  Gadirov

Dear Vagif,

The specification of  CG-5 Scintrex Autograv seems good in terms of accuracy, ease of use and the light weight.. This will probably increase the productivity of gravity data which is great. 

Kind Regards,

Nadim