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The choice of anti-theft detector

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The choice of anti-theft detector Powered By Docstoc
					The choice of anti-theft detector
Detector and public safety has a very close relationship, but often there are false
alarms problem. Select a good detector performance, the user can reduce a lot of
trouble, engineering companies can also reduce the number of after-sale problems.
Face many of the manufacturers are not familiar with the probe function, works on
how to choose? This paper from the manufacturing process and so detectors to discuss
the choice of detector.
   Main components
   The main components of the general detector infrared sensors, microwave detection
chip, ASIC chip, a few lenses and other components, the following main parts from
the analysis of detector.
   Infrared sensor
   As sensor technology matures, infrared sensors wider range of applications, such as:
infrared sensor switch, depending on the needs of many different models, and apply
anti-theft alarm sensor accuracy, angles, materials, storage temperature range
operating temperature range and other technical indicators have high demands, these
indicators or even directly determines the detector specifications. According to the
internal sensor to detect the number of atoms can be divided into units, dual, four
element infrared sensor, and now more and more applications are binary, some
manufacturers to achieve technological breakthroughs, start Application of Four
infrared sensors.
   Domestic and foreign well-known higher German Hyman infrared sensors, the
sensor surface Haiman logo; Japan Nisai La is also a high profile brands, the
production in Shanghai; domestic production sensor manufacturers are also many, and
some exports, But visibility is not very high. Domestic manufacturers and foreign
brand-building there is a great gap between the domestic product because there is no
brand, the competition always give a hybrid brand, quality, sense of instability.
Foreign brands of detectors in the sensor of choice has Haiman logo more
consideration to the German sensor; many domestic manufacturers consider the cost,
no-tag multi-domestic production of the sensor. In contrast, well-known brand in the
stability and quality can be better guaranteed. For example, when computer makers in
the introduction of machine will be also the main components of its advocacy, on the
one hand increase the component manufacturer's brand, while also
strengthening the trust of clients machine, can be a win-win choice.
   Fresnel lens
   The main function of Fresnel lens is to detect the infrared space effectively
concentrated on the sensor. Through the lens of the concentric circles located in the
narrow-band (Windows) is used to achieve the aggregation of the infrared equivalent
of a convex lens effect. Select the key is how this part of the lens design and lens
material narrowband. Consider the lens parameters are: luminous flux, different lens
concentricity, thickness nonuniformity, shape concentric with the lens axis,
transmission, focal length errors. Fresnel lens narrowband (window) design is
generally uneven, divided into several rows from top to bottom, the top more, below
less common among intensive and sparse on both sides. Because people face, knee,
arm, strong infrared radiation, just in front on top of the lens; below less, first,
because the lower body is weak infrared radiation, and second, to prevent interference
with terrestrial animals and infrared radiation. Material usually with plexiglass.
   Now many manufacturers, technology or lack of funds, free to choose to match the
lens and the sensor, and even some manufacturers to save costs, function, detection
range of different detectors actually select the same lens, which has great influence on
the detector performance. Because good design has a fixed focal length lens and the
curvature of the detector position sensor location in the Fresnel lens focal length is
matched, the detector can achieve optimal performance. As a convex lens as the focus
of the position only until the formation of a light point, to focus on the best, too close
or too far will affect the detector performance. Many manufacturers choose the lens
thin, luminous flux of the target can be achieved, but the condenser and the effect of
light and dark area will not be very good, thus affecting the optical properties of the
detector, leading to sensitivity, detection range of parameters such as instability
situation.
   ASIC IC
   With SCM technology matures, the choice of more and more chips, the chip also
determines the function of many of the technical parameters of the detector, such as
pulse detection mode. But many manufacturers of IP-based considerations, the type
hiding chips, it is difficult to judge from the surface quality of the detector. But the
chip's stability, maturity of the detector's function is to have a
great impact.
   Microwave detection chip
   Microwave probe chip design is generally several bands according to the national
to design, publish the current state of the band, including three groups: k-band, s band,
x-band (frequency number can refer to the specific national standards), manufacturers
in the design time can be different bands, but the band shaped graph (that is, detection
range) is not the same, this is the level of the company's design. But the
principle is the same as that of microwave radar and infrared detection range of a
good compound to achieve Shuangjian the best results.
   PCB
   As the integrated circuit board is now relatively high, mainly to see the circuit
board design rules, surface cleanliness, whether idle circuit board and PCB solder
hole is closely combined with the housing and other factors. Although this is not the
major factors, but can these details can show the overall strength of the manufacturer.
   PCB rules may reflect the early designs of well, we can see whether the product
design, manufacturers have taken note of the beginning of the factors that can trigger
false positives; circuit design is too complicated or improper arrangement is also a
technical immaturity. In addition, the sensor pin bending or welding parts, leave the
pin above the base of 4mm.
   Poor surface cleanliness detector on the one hand reflects more product manual
processing, on the one hand reflect the manufacturer is not very strict production
management. Detector is a special product, if the attention to detail, will be the impact
of very large systems. For example, thousands of detectors used in a project, if there is
a false alarm detector once a year, then several times a day should be ten times or
even the entire system of false positives.
   Board has solder holes idle, there may be two reasons: First, the original design is
not comprehensive, resulting in redundant circuits; the other is the lack of weld
components, fewer components Imagine products, you can guarantee you it is very
stable ? This product is best not to choose.
   Circuit board must be closely combined with the shell, or as the movement of
circuit boards causes the position sensor is not fixed, it will inevitably affect the
stability of the detector, failure to report the situation may occur.
   Generally around the sensor with a ceramic piece to protect the sensor, mainly
around the heat sensor to prevent radiation, electromagnetic radiation impact sensor
performance, also makes a more stable fixed sensors in the circuit board. The details
can be fully reflects the manufacturer's professional.
   Shell
   Many detector shell is used in the design of the public model, some of their own
design mold because there is no consideration to the lens focal length, the shell of the
IP rating and other factors, although it would be more beautiful appearance, but the
applications are relatively poor.
   Case, regardless of not only beautiful, but also needs to be done relatively smooth
surface of the other materials to do the aging treatment, so as not to appear with a long
time after bleaching, etc., affect the image of the room.
   Detectors should also be considered in the design of indoor dust, and easy to do not
only open the detector, but also consider its seal. Waterproofing outdoor detectors
need to consider the issue, the general increase in the washer designed to ensure that
outdoor adverse weather conditions, the detector can maintain their normal work.
   Manual
   Brochure should not just use the detector, the detector should also include some
basic information, such as national standard [see "GB10408.5-2000
intrusion detectors Part 5: Passive infrared detectors" on the instructions
part of the requirements]. But now there are many manufacturers because of limited
strength not to do in accordance with standard specifications, or even were no
instructions.
   Conclusion
   Initial contact detector, the above aspects can be made with the preliminary judging,
of course, the most important thing is to look at the actual re-testing, practice is the
sole criterion for testing truth. These are just some superficial ideas please enlighten
me!
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