?1CHAPTER 1 INSTRUMENT OVERVIEW The Burris Gravity MeterTM was designed to eliminate the need to purchase a separate meter for microGal applications*. The UltraGravTM control system allows the user to choose the level of accuracy needed for each application. Lower accuracy results in faster reading times, allowing more stations to be logged in a day. Higher accuracy allows the Burris Gravity MeterTM to be used for the most demanding microGal surveys. The Burris Gravity Meter™ can be configured for your specific application needs. • Petroleum Exploration • Mineral Exploration • Civil Engineering • Regional Geological Mapping • Geotechnical and Archaeological Exploration • Groundwater and Environmental Studies • Tectonic Research • Volcanology Research • Geothermal Research • Your Specific Application Whatever your level of experience, UltraGravTM makes using the Burris Gravity MeterTM fast and easy to operate. When configured for automatic readings, students and beginners can sit back and let UltraGravTM do all the work. Professionals and experienced operators can customize UltraGravTM for more complex scenarios. In addition to single-mode operation, continuous-mode operation permits earth-tide and secular recordings. If speed is of the essence, menu selected precision allows you to choose the desired level of precision for the job: the lower the level of precision, the faster the reading. UltraGrav™ also provides for the meter to be operated remotely through a serial cable, or optional wireless connection. A microprocessor-based automatic reading and data logging system, UltraGravTM controls the meter for blunder-free observations. UltraGravTM does all the work for you. It takes the reading, applies the calibration factor, corrects for earth tides and level position (when user enabled), then stores the data and displays the results. UltraGravTM comes installed on a PDA (Personal Digital Assistant) for flexibility in the field. The computer can be placed atop the meter or detached for hand held operation. With the optional wireless PDA module, it is no longer necessary to stand beside the meter for operations. The observer can be free to do other tasks while monitoring the gravity meter at a distance. UltraGravTM also allows the meter to be remotely monitored and operated via serial cable. Each Burris Gravity MeterTM is built around a handcrafted, metal, zero-length spring. ZLS springs have extremely low hysteresis and drift rates. When new, ZLS springs typically have ??????????????????????????????????????? ???????? ?? ?? ????????? ? ? ? ????? ??? ???? ??? ?????? ?? ???? ????? ?? ??? ? ? ??????????? ?????? ?? ? ???? ???2drift rates of 1.0 to 2.0 mGals per month. When mature, the drift rate is typically less than 0.5 mGal per month. Data have shown that the spring' s drift rate improves with age. The prototype has a drift rate of approximately 0.030 mGal per month. UltraGravTM provides unsurpassed precision and accuracy. A type of micrometer screw error known as circular error (periods of the order of a turn of the screw or less) is eliminated when measurements are taken within the range of the feedback system. Calibrated screw meters are calibrated every 50 mGals over the entire 7,000-mGal meter range. Calibration values are stable over time as they are determined by a hardened micrometer screw. The Burris Gravity MeterTM has consistently yielded standard deviations of 0.003 mGal or better during routine field tests. The Burris Gravity Meter™ leveling system is fast and easy to use. It consists of a detachable level plate and base plate. The level plate and base plate are held together by articulating clamps and can be carried as one unit. Used in this configuration the meter can be read in areas without a solid surface to place the meter on. When a pier, sidewalk, road, or solid surface is available, the meter can be used with the level plate attached to the meter or carried separately. Under normal field conditions, the Burris Gravity MeterTM can be precisely leveled for MicroGal readings within 30 seconds. However, precise leveling is not required as UltraGravTM performs automatic level corrections (when user enabled). The level plate has a wide base for stability. ZLS can customize the thread pitch and length of the leveling legs to fit your particular application. Unlike bottom leveling systems where the meter is placed blindly into slots, the Burris Gravity Meter TM is easily placed between the level legs. With the ZLS leveling system there are no motors to reduce battery life or break down during a survey. The Burris Gravity MeterTM contains the sensor, electronics, computer and battery all in one easy to handle unit. There is no need for a separate carrying case and time is not wasted taking the meter in and out of a case. The Burris Gravity MeterTM is sealed to keep out the wea。