GeoSIG AC-7x Accelerometer

Key Features

  • True Electro-mechanical
  • Force Balance Accelerometer
  • Digital AC-73D version available
  • Dynamic Range 165 dB
  • User selectable Full Scale range
  • ± 0.5, 1, 2, 3 or 4 g
  • Bandwidth from DC to 200 Hz
  • Exemplary Offset stability
  • Temperature and drift compensation
  • Robust suspension system
  • Single Bolt Mounted Enclosure with
  • up to ± 10° of Leveling Adjustment
  • Integrated Bubble Level
AC-7x Accelerometer
   


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DATASHEET
MANUAL

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Click here for the AC-73 accelerometer response files in the IRIS NRL library


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 up to 1000 meter distances using standard Cat5e cables, providing an extremely compact and versatile measuring solution.

  • General Characteristics

  • Versions:
  • AC-7x: analog 
  •  
  • AC-7xD: digital
  •  
    Configurations***: Triaxial Biaxial Uniaxial Axes Alignment**
    AC-73 or AC-73i*  X     X – Y – Z H – H – V
    AC-72-H or AC-72i-H*    X   X – Y H – H
    AC-72-HV or AC-72i-HV*    X   X – Z H – V
    AC-71-H or AC-71i-H*      X X H
    AC-71-V or AC-71i-V*      X Z V
  • * i : Internal sensor   ** H: Horizontal, V: Vertical ***: add “D” after number of channels for digital version 
  • Full Scale Range:
  • ±2 std., ± 0.5, 1, 3 or 4 g user selectable at field

  • Sensor Element

  • 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
  • Damping
  • 0.7 ±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:
  • 47 Ω

  • Power

  • Supply voltage:
  • AC-7x: 9.5 to 18 VDC, single supply
    AC-7xD: 48 VDC
  • Consumption:
  • AC-73: 41mA typical, 260 mA max. @15 VDC
    AC-73D: 200 mA typical
  • Overvoltage Protection:
  • All external interfaces are protected

  • Connector Pin Configuration

  • AC-73:
  •  
  • Pin 1-2, 3-4, 5-6:
  • Signal output for axis X, Y, Z
  • Pin 7-8:
  • Test input, Digital 0/12 V / GND
  • Pin 9-10:
  • 12 VDC insulated power supply input
  • Pin 11-12:
  • Reserved
  • Case:
  • Shield connection
  • AC-73D:
  • see user manual

  • Environment/Housing

  • Housing Type:
  • Cast aluminium
    Sealed access cover
  • Housing Size:
  • 195 x 112 x 95 mm
  • Weight:
  • 3.0 kg
  • Index of Protection:
  • IP 65 optional IP 68*
  • Temperature Range:
  • -20 to 70 °C (operating)
    -40 to 75 °C (non-operating)
  • Humidity:
  • 0 to 100 % (non-condensing))
  • Orientation:
  • Can be configured for mounting in any position (please specify at order).
  • Mounting
  • Single bolt, surface mount, adjustable within ±10°

  • Standard sensor

  • Floor mounted, Full scale ± 2 g, for external sensors: concrete anchor, GeoSIG recorder mating connector and
    AC-7x: 2 m cable with cable inlet
    AC-7xD: cable inlet

  • Options

  • Full Scale Output*:
  • 4 to 20 mA current loop*
  • Cable & connector*:
  • -Frame connector (no cable inlet)
    -Mating connector (for frame connector)
    -Cable with shielded twisted pairs for any with open end
    -Connector on user specification mounted at cable end
    -See separate cable & connector options sheet
  • Housing:
  • -Watertight IP68 housing*
    -Stainless steel protective housing
  • Mounting:
  • See separate sensor orientation options sheet

  • Ordering Information

  • Specify
  • Version and configuration of AC-7x, full scale range, and other applicable options

  • *NAD: Not applicable for AC-7xD digital version

    **Specifications subject to change without notice