PIR's: Why trip on two detects?

Good idea, thanks I'll try it. It's just tough because the range is just a silly dial, no markings or anything, just "min" and "max". I'm guessing that midway is half the max range distance (25') but who can really tell... I have to set it, pop the face back on, walk to the wall and wait, then try to flail my arms. My wife thinks it's quite amusing actually.

Poping the face back on or flailing your arms?

The Sentrol AR 435 for one and I think some of the Visonic dual tec's also.

I've got one application in a big mansion where the owner doesn't want to have detectors seen is some areas. At the top of his main stairway there's a very expensive painting. I have an AR435 in an adjacent area set at microwave only, looking through the wall at the area on the stair landing.

She just rolls her eyes at the whole process. I set everything to minimum distance and it still trips at the furthest point of the room so we'll see if this fixes the problem...

I know the AR 435 can be set for microwave-only, but that's not quite what Frank was talking about originally. He was mentioning a dual tec that would go into alarm if either the PIR or the microwave was tripped. I don't know whether any of the Visonics do that.

I wouldn't think there'd be too much demand for it. Instead of reducing false alarms, such a detector would increase them, as anything that would trip either technology would cause an alarm.

So far so good. A day later and no trouble yet.

hmmm ..... Sorry ..... but I missed that.

I don't know of any motion detector that does that.

Yeah, but I bet it would sell for a really low price!

Just keep in mind that the adjustment is only affecting one of the technologies, most likely the microwave sensitivity. The PIR is still detecting at the maximum range of the unit. So the PIR LED will still come on at the maximum range but not until you get in range of the microwave, will the alarm LED come on. Also, keep in mind that adjusting the range of the microwave will only reduce the sensitivity to moving objects the aproximate size of a person. A larger moving object, further away, may still cause the microwave detector to trip. The Sentrol AR 435 and related motion detectors are the only ones that I know of that you can limit the range of the microwaves detection field.

On the Visonics, it'll do that in "test" or "set up" mode. I came across two installations on take-overs where the tech had left the sensor in MW test mode (PIR off). I wouldn't recommend leaving them there personally. You're not getting the "best bang for your buck" if you do that (the benefit of using both technologies).

ISTR Racal (Chubb's parent company in the '80's) had a couple of dual technology sensors you could set up that way thereby eliminating the need to sell two different types of sensors. Depending on the environment, you could activate one, or both. I don't remember the part number, but I still have a some old price sheets around here somewhere. I'll look for 'em over the next couple of days and post the PN's.