Seismic Protection.
Sensonics manufactures a range of devices for the measurement and monitoring
of seismic activity in the vicinity of industrial or civil installations.

Seismic Switches


SA-3 Safety Seismic Switch

Sensonics type SA-3 safety seismic switch is a tri-axial vibrationdetection device, suitable for the protection of vulnerable structuresfrom seismic events. The unit features three high sensitivity low
noise seismometers and high integrity alarm circuitry. The switch is seismically, qualified and features an optional 2 out of 3 voting system.

The switch operates on seismic events and when the signal from any axis exceeds the pre-set alarm level, the alarm relay is activated.

Failure of any sensor or of the power supply will also cause an alarm relay to be activated. The contact changes from these relays are available for external use.

The detectors of the triaxial seismic switch are high sensitivity piezo-electric accelerometers. The low frequency cut-off point is set to 0.1 Hz (-3dB). The three detectors are positioned at 90° to each other in the robust steel box together with the associated electronics. Each of the detector channels consists of the accelerometer, a pre-amplifier and a compensating amplifier. This latter stage compensates for sensitivity changes of the piezo-electric crystal at different temperatures. The output signal is biased to a DC level and the vibration AC signal is superimposed on the DC voltage. Both the DC and AC voltages are set within +1- 2% tolerance to enable the user to change the accelerometers without re-setting any of the other stages in the seismic switch.


Digital Seismometers

Recording and Relay Systems

Alarm Voting Systems
Sensonics is an approved supplier to the UK power industry with systems in
use at all of its nuclear power plants.