It's not just the earthquake that causes damage to property, much of the damage is caused by secondary effects such as flooding, fire and explosions. A way of isolating the source of these disasters is an extremely valuable insurance policy. Similarly, expensive machinery can be shut down before it is subject to the full effect of earthquake generated forces.

An earthquake generates two types of shock waves: the pressure waves (P-waves, which produce predominantly vertical accelerations) and the sheer waves (S-waves). The S-waves do all the damage but they travel from the earthquake epicentre more slowly than the P-waves. The P-wave can arrive seconds before the damaging S-waves.

Solid State's Earthquake Trigger continuously monitors all components of the earth's acceleration due to seismic forces. It is designed particularly to detect the faster moving P- waves. When the acceleration exceeds the pre-set level the output relay changes state until 8 seconds after the quake. Contacts on this relay may be used to initiate any desired action. The unit has an event counter mounted on the lid to record the total number of operations, including instrument test operations.

AC Option

The transformer provides a float charge for the nine cell Nickel Cadmium backup battery. Should the mains fail, the NiCad battery will power the circuit for approximately 24 hours.

DC OPTION

This is used for DC operation from an external no-break battery system 24 V DC. This option does not require the internal backup battery.

Mounting

The site of installation of the Earthquake Trigger is critical to its performance and reliability. All of the points below should be taken into consideration when choosing a site.

A single 6 mm masonry anchor through the hole in the centre of the aluminium base and into the concrete will hold the Earthquake Trigger down firmly on its three feet and will prevent it rocking. This masonry anchor should not be over tightened as this can damage the cast aluminium case. Tighten the nut finger tight and then apply ~½ a turn with a wrench.

Wiring

Two M16 holes have been provided for cable entry.
Use a bung on any unused cable entry.
Wire the unit as required but take note of these points.

AC OPTION: terminal strip wiring

DC OPTION: terminal strip wiring

Commissioning

The setting of the sensitivity is determined by the application. If false triggering is acceptable but any slight earthquake must be detected using the more sensitive settings 0.012 g or greater. Conversely, if false triggering is unacceptable and only large potentially damaging earthquakes are required to be detected using the least sensitive settings 0.2g or less. The sensitivity is determined by the setting on a DIL switch accessible through a hole in the internal shield over the printed circuit. The settings for this are as follows:

As earthquakes of sufficient magnitude to trigger the device are rare, it is desirable to set up a regular maintenance schedule to check correct operation and consequent action on the protected equipment. All counter increments should be accounted for and noted in the log. Either it was a test a false trigger or an earthquake. If there are too many false triggers due to a poor site or inconsequential earthquakes then reduce the sensitivity.

To test the trigger on its most sensitive range, just touching the case with a screwdriver will trigger it.

A good test with just switch 4 on is to strike the concrete firmly with a heavy hammer close by.

Our recommendation is that a log is kept of tests (see appendix for format). Shock testing should be conducted at installation and at every 6 months.

The data may be recovered via the USB port but currently only at the factory.
The battery should be replaced every 5 years.

Power Supply Requirements:

AC OPTION: 230 V +/-10% 50 Hz Sine wave 3 VA. The AC option provides NiCad battery back up. This maintains correct operation for up to 24 hours

DC OPTION 1: 24 V DC (+ 10% - 30%). at 20ma standby.

DC OPTION 2: The DC options do not have internal battery backup.

Sensitivity: Selected by internal switch to one of the following 0.012, 0.025, 0.050, 0.100, and 0.200g. The sensitivity is to any direction of the acceleration. (1g is an acceleration of 9.8 m/s2 or 1000 mg.)

Frequency Response: Flat from 2 Hz to 10 Hz (+/-3 dB). 10 dB down at 20 Hz.

Operation Time: Relay fully actuated within 10 ms from the time of the first shock of 3 from the earthquake that exceeded the set acceleration. The relay is de-energised 8 seconds from when the set acceleration level was last exceeded.

Event Counter: A 6 digit counter which records the total number of operations. (Tests, false alarms and earthquakes)

Contact Ratings: OMROM LY2 RELAY 10A at 230 VAC, 3A at 24 V DC resistive, 2A at 24 V DC inductive, 0.6A at 110 V DC resistive, 0.4A at 110 V DC inductive.

Weight: 3 Kg

Size: 290 x 220 base (mm), 90 mm high

Construction: The unit is housed in a substantial cast aluminium casing, painted with a white polyester finish.

EARTHQUAKE TRIGGER S/N. ........................... LOG