Motion Detectors view an area watching for "INFRARED" changes, detectors view rooms, people and animals differently -- similar to this

The detectors basically view the room “thermally”, when you walk into the room you change the “Thermal Picture” that the detector is viewing.
Depending on the quality of the detector and design, certain detectors can tell the difference between say a small dog and a child though different radiated Infrared signals from each of them.

Passive [Waiting for a change to be transmitted to them from your radiated infrared energy] detectors are sometimes susceptible to air drafts, reflected light from pools in their view, crawling insects.

Microwave type detectors are Active, which means they transmit their own signals, these signals then bounce back to the detector and the microprocessor then analyses the received signals and looks for changes. Microwaves generally aren’t affected by air draft movement – only solid objects. Microwaves have to be carefully placed though as they can also see through Glass and other objects whereas Passive type detectors don’t.

  Generally No Airdrafts, Crawling/Flying Insects, Birds and generally for sealed rooms

  Tell the difference between say Cats/Small Dogs and Humans

  These basically have 2 standard type sensors built into one housing, although the sensor element [Pyroelectric] has a different geranium filter and is a dual element, thus having two dual elements equals a Quad. The 2 elements are slightly apposed to each other. This slight offset means the individual elements don’t see exactly the same movement creating a better false alarm resistance – Ideal for most situations as is more tolerant to environmental changes and some are immune to insects.

  This is usually a Standard Sensor and a Microwave built in as well, both technologies need to be activated before the detector will activate the alarm. In an harsh environment situation remember that some only have a Standard Pyroelectric with the microwave which could make that part of this dual technology always in an "active" state if placed in say a drafty environment leaving all the detection still back on one method being the microwave.

  This is a New Technology that should someone accidentally or deliberately block the detector by say placing a box in front of it, the detector can still see through the box and pick up moving objects. The technology is a lot more indepth than can be explained here.

  This type of detector can be programmed to look for movement during a defined period, say 24 hours. If it doesn’t pick up movement in this time is activates a trouble alarm to advise you to investigate the detector.

  Should someone try to block the detector when the security system is turned off with a spray of some description, there is an inbuilt sensor that can detect this. Caution for the owner of these detectors as normal surface spray can also cause them to go into alarm.

  There are a lot of wireless detectors on the market which communicate to the alarm panel via a wireless transmitter and receiver. The detector obtains its power from a long life lithium inbuilt battery. Any Quality wireless detector should have a supervised signal, this means it sends like a “Test” to the alarm panel at certain times and the alarm panel looks for this signal to make sure the detector is still functioning [usually 1 hour]. The detector should also be able to transmit Tamper Alarms, Low Battery and of course intrusion detection. Average battery life depends on the Quality of the detector, most range up to 3 years or so.

  Detectors range on price depending on features usually starting at $140.00 if done at time of installation.

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