OPERATION MANUAL - Scintrex

Spring Service Life and Reading RangeThe uncorrected gravity reading is obtained as shown from Equation (B.4) onpage B-9. The gravity reading range has high and low end, the range ofwhich is guaranteed to be 8000 mGals, but is normally much larger. The lowend of the gravity measurement range of the CG-5 may be calculated byinserting value (SF/SC) = 0.1 into Equation (B.4)SU min = 0.1 * GCAL1 + 0.01 * GCAL2(B.1)Note:GCAL2 has been permanently set to zero in theCG-5 instrument.The average value Of SU min is about 600 mGal. Depending on the valuesGCAL1 and GCAL2, this value may differ somewhat for your meter It isrecommended that you calculate this value for your meter, because thegravity readings of lower values than SU min may not be accurate.The high end of the gravity measurement range may be calculated byinserting value (SF/SC) = 1.457 into Equation (B.4)SU max = 1.457 * GCAL1 + 2.123 * GCAL2(B.2)The average value of SUmax is about 12000 mGal. Depending on the valuesGCAL1 and GCAL2 this value may differ somewhat for your meter. It isrecommended that you calculate this value for your meter, because thegravity readings of the higher value than SUmax may not be accurate.The CG-5 sensor spring position is adjusted during the sensor manufacture insuch a way that, on average, the gravity reading in Toronto (latitude 43.7degrees) is about 4200 mGal. This, in conjunction with the gravity readingrange of about 8000 mGals, assures that a newly produced CG-5 maymeasure the relative gravity anywhere on the surface of the earth, fromelevations of a few thousand meters above the equator to sea levels at bothpoles. For your convenience, values of normal gravity at sea level, as afunction of latitude, are listed in Table 1 on page B-8.B-6CG-5 Manual - part # 867700 Revision 2