Instrumental Software Technologies Inc ISTI - Products - Accelerometers - GEObit SM1500

Products

 

Accelerometers

 

GEOfba200 Force Balance Accelerometer

OVERVIEW

The GEOfba200 (Fig. 1 - 3) is a very low-noise triaxial force-balance accelerometer with a large dynamic range, suitable for seismology, hazard mitigation, and civil engineering applications. The instrument has a flat response to ground acceleration from DC to 215 Hz and a stable phase response within the passband. The output range is 40Vpp differentially and supports a variety of gain settings from +/-4g to +/-0.25g in the standard configuration and higher gain settings upon request.

+ Additional Details

Due to its high dynamic range exceeding 155dB, the sensor provides on-scale recording for applications ranging from free field strong motion to structural monitoring. It also allows engineers to study motions at higher frequencies. The sensor enables easy field calibration through its calibration line.

Inside the GEOfba200, there are three similar accelerometers placed orthogonally. The sensor operates according to the force-balance principle as a closed-loop sensor (servo accelerometer).

The motion of the seismic mass is monitored from a very sensitive capacitive transducer and a very low-noise VHF preamplifier. The demodulator generates an in-phase and low-noise seismic signal fed back to the seismic mass through a phase compensator, a power amplifier, and a fully symmetrical force actuator consisting of a double coil-magnet system. This design eliminates any non-linearity due to a lack of symmetry. The output amplifier sets the selectable acceleration gain between +/-4g to +/-0.25g.

+ Features

  • Low noise accelerometer for high precision and high dynamic range
  • Selectable full-scale range +/-4g to +/-0.25g standard, higher gain set custom available
  • Wide passband DC to 215Hz, higher corner frequency custom available
  • Simple installation using a central fix bolt
  • Electronically adjustable DC offset
  • Power 9-18Vdc, 1.2W
  • Waterproof IP68 aluminum or stainless-steel casing
 

THE SM1500 & SM550 STRONG MOTION ACCELERATION SENSORS

OVERVIEW

The SM550 and SM1500 (Fig. 4 - 6) are MEMS-type, three-component acceleration sensors. Both have wide frequency responses. The SM1500 model responds from DC to 750 Hz, while the SM550 model responds from DC to 50 Hz. Many output ranges are available for both models: +/-2 g, +/-4 g, +/-5 g, +/-6 g, +/-10 g, +/-12 g. The default sensitivity is 2.4 V/g for the SM1500 and 1.2 V/g for the SM550.

+ Additional Details

The SM1500 and SM550 accelerometer technology is based on a variable capacitor transducer and a feedback circuit that operates in a closed-loop configuration. The feedback force is controlled by an application-specific integrated circuit (ASIC), which provides high reliability and low-output noise.

  • The SM1500 and SM550 sensors operate from a 12 V DC power supply ranging from 9 V DC to 18 V DC. The typical power consumption is 33 mA.
  • Acceleration output is differential analog, swinging between +/-5 V. Other output voltages are available.
  • 4 – 20 mA current loop output is also available for both sensors.
  • The default cable length between the sensor and the digitizer is approximately 2 meters, but it can be extended. The 2 – 40 mA version can have a long connection cable.
  • The sensors are surface- or wall-mounted over a provided adjustable base, which allows leveling and orientation.
  • Seismic accelerometers can be used for early warning systems implementation.

+ Features

  • Three-axis accelerometers
  • Ultra-low power consumption
  • Surface/wall mounting
  • MEMS (Force balance/ASIC technology)
  • DC – 750 Hz
  • Wide Dynamic Range 96 dB
  • Output range +/-2 g to +/-12 g linear
  • Noise level 6 ugrms/sqrt (Hz)
  • Operating temperature -20 to +70°C
  • Borehole type (optional)
  • 4 – 20 mA current loop output – NEW!