manufactures a range of devices for the measurement and monitoring
activity in the vicinity of industrial or civil installations.
SA-3 Safety Seismic
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
noise seismometers and high integrity alarm circuitry. The
switch is seismically, qualified and features an optional 2 out of 3 voting
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
Recording and Relay
Alarm Voting Systems
Sensonics is an approved supplier to the UK power industry with
use at all of its nuclear power plants.