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AC-73 / AC-72 / AC-71 Force Balance Accelerometer

Broadband Seismic, Earthquake and Structural measuring and monitoring

Features

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

Outline

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.

  • General Characteristics
      Конфигурация
        Triaxial Biaxial Uniaxial Axes Alignment**
      AC-73 или AC-73i*:     X – Y – Z H – H – V
      AC-72-H или AC-72-Hi*:     X – Y H – H
      AC-72-V или AC-72-Vi*:     X or Y) – Z H – V
      AC-71-H или AC-71-Hi*:     X (or Y) H
      AC-71-V или AC-71-Vi*:     Z V
      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 %
      Cross Axis Sensitivity < 0.5 %
      Bandwidth DC to 200 Hz
      Damping 0.7 ±0.1 critical
      Drift 0.0005 g / °C, 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
      Power
      Supply Voltage 9.5 to 18 VDC, single supply
      Consumption 55 mA @12 V
      Connector Metallic, Shielded, IP67, 12 pins, male
      Overvoltage Protection All pins are protected
      Connector Pin Configuration
      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
      Environment/Housing
      Housing Type Cast aluminium. Sealed access cover
      Housing Size 195 x 112 x 96 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 AC-7x Floor mounted, Full scale ± 2 g,
      2 m cable with cable inlet and GeoSIG
      recorder mating connector, concrete anchor
      and user manual on CD
      Options Full Scale Output: 0 to 20 mA current loop
      Cable & connector - Frame connector (no cable inlet)
      - Mating connector (for frame connector)
      - Cable with shielded twisted pairs for any length 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

      * i : Internal sensor
      ** H: Horizontal, V: Vertical

AC-73-DH / AC-72-DH / AC-71-DH Force Balance Accelerometer

Broadband Seismic, Earthquake and Structural measuring and monitoring

Features

  • 1 True Electro-mechanical Force Balance Accelerometer
  • 2 Extremely robust downhole housing
  • 3 Suitable for borehole diameters of 100 mm and larger
  • 4 Dynamic Range 165 dB
  • 5 Full Scale ± 0.5, 1, 2, 3 or 4 g
  • 6 Bandwidth from DC to 200 Hz
  • 7 Temperature and drift compensation
  • 8 Robust suspension system
  • 9 Proprietary iSensor™ interface
  • 10 Built-in compass as well as tilt, temperature and humidity sensors

Outline

The AC-73-DH sensor package is a true electromechanical 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-DH 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-DH 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-DH 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-DH without mechanical offset adjustment and fine levelling.

The advanced iSensor™ interface allows easy deployment using built-in hardware like compass as well as tilt, temperature and humidity sensors.

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.

  • General Characteristics
      Конфигурация
        Triaxial Biaxial Uniaxial Axes Alignment**
      AC-73-DH*     X – Y – Z H – H – V
      AC-72-H-DH*     X – Y H – H
      AC-72-V-DH*     X  – Z H – V
      AC-71-H-DH     X H
      AC-71-V-DH     Z V
      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 %
      Cross Axis Sensitivity < 0.5 %
      Bandwidth DC to 200 Hz
      Damping 0.7 ±0.1 critical
      Drift 0.0005 g / °C, 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
      iSensor™ interface The hardware and software allow to manage, control, recording and transmission of data, including the management of applications for embedded:
      - compass
      - tilt sensor
      - temperature sensor
      Power
      Supply Voltage 9.5 to 18 VDC, single supply
      Consumption 80 mA @12 V
      Connector Metallic, Shielded, IP67, 12 pins, male
      Overvoltage Protection All pins are protected with double stage barrier
      Connector Pin Configuration
      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 iSensor™ interface (RS-485)
      Case Shield connection
      Environment/Housing
      Housing Type Aluminium. Optional Stainless Steel
      Housing Size Ø 89 mm x 502 mm
      Weight 4.2 kg (typical configuration)
      Index of Protection Watertight upto 10 bar (100 m)
      Temperature Range -20 to 70 °C (operating)
      -40 to 75 °C (non-operating)
      Standard AC-7x-DH Full scale ± 2 g,
      with cable inlet and user manual on CD
      Options
      Cable & connectors - See separate cable and connector options sheet
      - Connector on user specification can be mounted at cable end

      ** H: Horizontal, V: Vertical