Sigma Ʃ force feedback accelerometer is based on a truly rectilinear suspension system. Three axis strong motion accelerometer is housed in an ‘O’ ring sealed hard anodised waterproof aluminium case.
The system is self-contained, except for the power source. An isolated dc-dc converter ensures galvanic isolation of the system and operates from 9 to 36 Volts.
Figure 1 Feedback accelerometer with Mil-Spec connector.
The SIGMA is a compact and robust FBA triaxial accelerometer with an exceptional performance, suitable for local and regional recording and for earthquakes engineering applications.
The analogue feedback accelerometer has an extremely large dynamic range exceeding 157 dB at 1Hz.
The sensor Analogue differential outputs are interfaced to the differential inputs of the digitiser.
The photo Figure 1 shows the sensor Mil-Spec connector turret. The connector turret allows easy connection to the sensor. All the connectors are waterproof with O ring seals to a depth of 2 meters of water.
Full-scale low and high gain sensitivity is digitally user-adjustable from ±4.0 g to ±0.5 g on all components of the sensor.
The standard frequency pass band is flat to acceleration from DC to 350 Hz.
Detailed sensor calibration information is provided with every sensor, including sensor dc calibration levels, frequency responses of the instrument and the transfer function in poles/zeros notation.
It is extremely simple to install sensor, single point slotted base bolt point ensures that the sensor to be fixed firmly to the installation point. Three leveling feet ensure that the sensor to be leveled and locked to the installation bolt.
The North/South ordination points are machined on the sensor base and the sensor component fixing crews are fixed with dowel pins to achieve highest possible orientation accuracy. The errors in pointer to the sensor orientation is less than ± 0.1 degrees.
After installation the sensor output offsets are nulled electronically, without exposing the insides of the accelerometer.
The digital sensor noise performance is better than 0.15 µ m/s2/√ Hz. The sensor dynamic range exceeds 157 dB at 1Hz.
The accelerometer is provided with different connector options. Either with Gaiacode D type waterproof connectors or Mil-spec. connectors.