WALK TESTS
Walk tests are mandatory to ensure that the installed motion sensor operates as expected. The reliability of a motion sensor is often compromised when the installer fails to test the sensor and make adjustments according to site conditions. Walk tests should be done by moving across the detection area from its outermost limits. These should be repeated at 2- to 3-foot intervals, each time moving closer toward the sensor.
Typically, the motion sensor has LED indicators that will light up when it detects motion. It is important to read the manual in order to understand what these LED indicators mean as sensors from different manufacturers behave differently.
ALARM CONTROLLERS
Since the control panel ultimately makes the decision if the signal from the sensor indicates a valid intrusion event, it is possible to have features within the panel to drastically reduce false alarms.
Motion sensors are connected to control panels as zone inputs. Each zone input or group of zones may represent a specific area within the protected premises. The control panel can be programmed to react differently when motion sensors activate. For example, the system may initiate a built-in delay timer and activate the siren only upon the expiry of the timer; or, it may activate the siren immediately. This is known as “zone type” programming; it is important that the appropriate zone type is assigned in order for the system to function properly.
One useful function that is commonly found in mid-range intrusion detection systems is “cross zone.” The cross zone function can reduce false alarms that are caused by house lizards and other pests. When the cross zone feature is enabled, the controller requires a minimum of two zones to be activated (that is, at least two sensors connected to two separate zone inputs to be activated, before an alarm condition is registered). This means that the system may require, for instance, a magnetic contact to indicate an opening door, followed by a motion detector catching a moving object. Since it is harder to activate two sensors at the same time, falsealarm reduction is achieved.
Another useful function is the alarm verification feature, also typically found in mid-range controllers. When an alarm verification is enabled for a zone input, the control system will require the same zone to receive the alarm signal from the attached motion sensor, not once, but twice before it decides that an alarm event has been detected. This feature is initially designed for fire alarm panels and is a false-alarm reduction requirement by ANSI/SIA CP-01 standards.
KNOW YOUR EQUIPMENTM
It is important to communicate your requirements clearly to your supplier in order to get the equipment best suited for your installation. At the same time, knowing your equipment well will optimize the overall performance of your security system. Remember to check with your supplier for any false-alarm reduction features such as the ones featured in this article, as different manufacturers may have different names to these features.