2) The 'dumb' end of the sensor is just a magnet. Why on earth it needs to be 3/4 long is something I don't get!!!
Well, I have your answer. It's long because almost the entire thing is a magnet! I broke one open, and inside was a single solid over 1/2" magnet.
I finally got my magnetic switches so I could test them on the windows.
I got the kind without a pigtail, which is what I REALLY want to use because I don't want a splice in the walls, no matter HOW good I make it. I got the kind with the pigtail, but with the "rare earth" magnet, which doesn't require any drilling into the sash (though it's mean to be screwed in). And I got the tiny surface contact ones.
I also got 50 of the tiny magnets, one if which is shown for comparison (1/4" dia, 1/32" thick).
I did some very ROUGH measurements of how big of a gap you could have between magnet and sensor and have it still work. That's a concern for me, as I feel that to wire the windows right, there is going to be a gap somewhere of some size. Here's what I came up with:
No pigtail:
Original magnet: Just over 5/8"
With 1 tiny magnet: 1/8"
With 2 tiny magnets: 2/8"
Pigtail/Rare Earth:
Original magnet: Just under 5/8"
With 1 tiny magnet: 1/8"
With 2 tiny magnets: 2/8"
Surface contact:
Original magnet: 1/2"
With 1 tiny magnet: 1/8"
With 2 tiny magnets: 2/8"
Some interesting note:
1) When I cut out the magnet from the plastic, and again checked the distance, you actually gained some gap (little less than 1/8"). Probably that's where the magnet was before, but this time without the plastic in front pushing the distance back. So, to have a bigger gap and to not have to drill so far into the sash, you're better off removing the magnet from the plastic and burying it directly, with some glue.
2) The small surface mount sensor (and it is indeed small) gained 1/8" in the gap when the magnet came in towards the edge, instead of straight towards the center. Must just be how the switch is oriented or wired.
3) It took about 3/8" in tiny magnets to equal the pulling power of the 1/2" magnet. So they are indeed stronger...but not by much.
I was impressed with the rare earth magnet, and I think it is going to be my choice. It was just as strong as the plastic shielded one, but wouldn't require me to drill a huge deep hole in my sash. I can handle putting a small screw in the sash. Also, the rare earth magnet that came with the switch is definitely stronger than the same thickness in tiny magnets.
I also was very pleased with the pigtail-less switch. It was very easy to insert and tighten the wires.
So, here's what I want. I want the sensor
without the pigtail and the rare earth magnet
instead of the plastic-enclosed magnet. The problem is....they don't come as a set that way. It looks like I'm going to have to order 2 reed switches for every one I need. Then I'll take the sensor from one and the magnet from the other....and then package the other sensor and magnet and I guess ebay them.
Shame I can't just find what I need as-is.