Seismic detector

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Seismic detector on the inside of the vault door

Seismic detectors (KSM) are used for detecting and reporting, associated with destructive force, intrusion in secure storage and spaces of steel or concrete (z. B. safe cabinets and safes module). They are part of burglar alarm systems .

functionality

The structure-borne sound detector uses a piezo element to record acoustic events within certain frequency ranges and evaluate them using an integrated processor. The main structure-borne noise is generated by the monitored material when changes in its structure occur due to intensive mechanical or thermal effects. This operating principle can also be used to detect “silent” attacks (e.g. with a cutting torch ).

Construction / installation

In technically up-to-date structure-borne sound detectors, the piezo element and evaluation electronics are combined in one housing. The device has a flat mounting surface with which it is screwed directly onto the surface to be monitored. The majority of the newly produced safes already have corresponding threaded holes. When retrofitting older safes, adapter plates made of steel are welded or dowelled. The seismic detectors are parameterized according to their application environment via DIP switches and external control inputs. Possible parameters are mostly the sensitivity and the number of events in a short period of time.

exam

Test transmitters, which are installed in the immediate vicinity of the seismic detector on the material surface to be monitored, are used for regular functional testing. When activated, these transmit vibrations in the critical frequency ranges to the material (generated by the seismic detector itself or by external control electronics).

reliability

Seismic detectors work very reliably with correct parameterization. False alarms are theoretically excluded due to the principle of action. In practice, however, there are phenomena:

Example bridge construction work

In the case of a reinforced concrete modular safe installed in the basement of a bank branch, several false alarms were triggered by the seismic alarms while a bridge was being replaced about 30 m away. The new bridge was built next to it before the old one was demolished and moved into position after it was dismantled. For this purpose, a "shaking technique" was used, which apparently caused the structure-borne noise that reached the safe in the critical area.

Example coin money

A seismic detector in a coin dispenser regularly caused a false trigger on the same days of the week at the same time. The evaluation of the transaction logs of the machine showed that it was precisely at this point in time that the owner of a nearby shop was always demanding the same quota of coins. In several practical tests it was shown that the seismic detector triggered "reliably" after around 50 ten-cent coins had been dropped quickly and evenly into the stainless steel output shaft.

literature

  • Georg Walz (Hrsg.): Manual of the security technology. Springer Verlag, Berlin / Heidelberg 1992, ISBN 3-642-95684-X .
  • Alfons Rempe: Practical manual for operational fire protection . Weka Media, Kissing 2004, ISBN 3-8111-5377-3 .
  • Dirk Bohne: Technical expansion of buildings. And sustainable building technology. 10th edition. Springer Fachmedien, Wiesbaden 2014, ISBN 978-3-8348-1832-4 .

See also

Web links