Automated Burris gravity meter for single and continuous observation

The Burris Gravity Meter;manufactured by ZLS Corporation, Austin/Texas, USA, is based on the invention of L&R（L. LaCoste and A. Romberg）: The ZLS（zero-length spring）. A digital feedback system（range of about 50 mGal） is used to null the beam. Now, more than 120 gravity meters of this make exist worldwide and are used successfully in exploration, volcanology, geodetic work and surveying.The sensor is made of the well-known（L&R） metal-alloy zero-length spring providing a low drift characteristic. The drifts observed are comparable to L&R gravimeters and are less than 0.3 mGal per month, which is much lower than the drifts known for the fused quartz sensors.The dial is calibrated every 50 mGal over the entire 7000 mGal meter range. Since the gravity value is determined at these points, there are no periodic errors. By a fourth heater circuit temperature effects are totally avoided. The gravity meter is controlled via Bluetooth;either to a handheld computer（tablet） or a notebook computer.The feedback responds with high stability and accuracy. The nulling of the beam is controlled by the UltraGrav;control system which incorporates an inherently linear PWM（pulse-width modulated）electrostatic feedback system. In order to improve the handling of the gravimeter we have developed two Windows based programs: AGESfield for single measurements and AGEScont for continuous readings.