I agree with you Strykrincognito and never meant to imply that the sensor "required" a ground plane to operate. However, I have found that reliability can be an issue if it is not mounted with metal behind it...which BTW it is on your vehicle by being mounted under the center console.
If the floor of your vehicle was not metal any small animal crawling underneath it would cause a false..but that is not really the concern with a ground plane.
This is what I have found can happen..lets say you decide to mount it behind the dash mounted vertically. Now it will still work..and it will still trigger the stages when the field is disturbed. Where you run into problems is with the field shape, I have seen it where it won't pick up being close to the vehicle..but a bird flying by sets it off, things like that.
I have a few incidences with these I can share although these circumstances have nothing to do with the ground plane, just general things that can happen with these sensors.
Once a customer complained that every time they parked and armed the alarm, it would false..but in a few minutes it would be fine. I found it was too many large things hanging from the rear view mirror as the culprit.
Had another time when the sensitivity was over sensitive in some spots..and none at all in others....coins in the console (it was mounted underneath like Strykrincognito did). It is a great location but these sensors can not see though metal...it only blocks and/or deflects the field in an unwanted way so you need to watch that.
I installed one in a large boat to protect the inside entrance and the customer said it would false at nights only..every time I went to check the system, it worked flawlessly. Turns out at night he raises the boat out of the water....a low hanging tree branch was the culprit...I cut it down and now all is well.
So you see there are some concerns with these type sensors. But I will add that they are probably the most difficult for a thief to get around, especially if they do not know you have one. I recommend them on every install and always use them in my own vehicles. Shock sensors are easily gotten around and EVERY system uses those so most thiefs already expect it and break the window with methods that do not impact the vehicle..but allow them entry through the broken window. A prox sensor will cover that problem every time. Also great for Jeeps and other soft top vehicles and allows you to leave the windows open and still have a form of interior protection.
But still do not leave anything of value in sight..no sensor can actually stop a thief from physically reaching in a grabbing stuff..even a blaring siren. Leaving a rabid dobermann in there might be more effective..lol
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Lynbrook NY
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