GeoSIG Ltd

GeoSIG Ltd

- Model AC-7x - Accelerometer



The AC-73 sensor package is a true electro-mechanical triaxial downhole accelerometer designed for broadband earthquake monitoring and applications requiring highly sensitive and rugged sensors with minimum maintenance and a simple method for periodic testing. The rugged mass suspension moving coil system improves the signal to noise ratio. The magnetic system and capacitive position sensors offer symmetrical controls for the accurate electronic centring of the mass. At rest the accelerometer mechanism is in balance and no electrical output is generated.

In case of a ground motion, AC-73 yields an electrical output proportional to the current used to keep the mass centred. This output signal is precisely calibrated to provide a signal at the utmost accuracy and with a lowest possible noise level. The symmetrical positioning system incorporated with the force balance accelerometer principle, the accelerometer faithfully keeps its scaling and calibration even under extreme conditions.

The DC response allows the sensor to be easily repaired, tilt tested or recalibrated in the field. With the help of the test line the AC-73 accelerometer can be completely tested assuring proper operation and accurate acceleration measurement. This test line is internally connected to the external world only when a given command is sent to the sensor to avoid any noise pick-up through the test input.

The AC-73 is equipped with electronic offset adjustment features that make its installation very user friendly. This powerful feature allows the users to install the AC-73 without mechanical offset adjustment and fine levelling.

The sensor can be powered from 9.5 to 18 VDC source with the advantage that its power input is insulated from the sensor’s electronic ground. This avoids ground loops and reduces noise induced through the power supply.

All the best features of the analog AC-73 accelerometers are now offered with the new AC-73D version, having a digital interface that is directly compatible to operate with the GMSplusD series recorders with upto 1000 meter distances using standard Cat5e cables, providing an extremely compact and versatile measuring solution.

  • Type: True Electro-mechanical Force Balance Accelerometer
  • Dynamic Range:
    • 165 dB (per bin rel. full range)
    • 156 dB (per bin rel. full scale rms)
    • 134 dB (0.02 – 50 Hz, integrated PSD
  • nonlinearity:< 0.1 %
  • Accuracy:± 0.4 dB max over the bandwidth
  • Cross Axis Sensitivity:< 0.5 %
  • Bandwidth:DC to 200 Hz
  • Damping0.7 ±0.1 critical
  • Offset Drift : 0.0005 g / °C
  • Span drift: 200 ppm / °C
  • Full Scale output: 0 ±10 V differential (20 Vpp)
  • Hysteresis: < 0.001 % of full scale
  • Sensitivity: 2.5 to 20 V/g
  • Output impedance: 100 ohms

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