OPERATION MANUAL - Scintrex

The spring temperature TEMP in units of mK can be displayed on the liquidcrystal display. The last TEMP value for each reading is also stored inmemory together with other measurement variables. The range of TEMP is±3.0 mK, and it is adjusted with a zero offset to within ±1.0 mK for normaloperation. This ensures that there is at least a 2.0 mK useful range tocompensate for severe ambient temperature fluctuations.The chamber temperature is measured by a set of two thermistors, whichthemselves exhibit a long-term drift due to their aging. However, the effect ofthis drift is indistinguishable from the gravity sensor drift, and is corrected bythe linear drift correction.Note:With the electronics used in the CG-5, there is norequirement for the user to adjust the temperaturecompensation as with previous meters. The systemhas enough dynamic range to accommodate anytemperature variations experienced with the system.Earth Tide Correction (ETC)ResidualsThe ETC is generated in the software via the Longman1 formula (gravimetricfactor = 1. 16) by entering in the latitude, longitude and difference betweenthe gravimeter clock time and GMT from the keypad. It is applied after thelast sample has been taken and it may also be disabled via the keypad. Thetime used in the tidal calculation is the midpoint between the start and the endof a reading.It is critical that the UTCDIFF (see page 2-7) is properly input into the CG-5.If the sign is entered incorrectly or the value is wrong because the localdaylight savings time shifts (summer time) are not properly accounted for,then the resulting corrections will be poor.The ETC will compensate for the gravity effects of the Sun and Moon towithin (usually) ±3 ugals. Tidal accelerations cause elastic deformations tothe Earth's body (earth body tides). The average effect of this deformation istaken into account by the gravimetric factor 1. 16 in the Longman formula1. Longman, I.M., Journal of Geophysical Research, Volume 64, No. 12, Formulas for Computing the TidalAccelerations Due to the Moon and the Sun, December 1959.B-20CG-5 Manual - part # 867700 Revision 2