On Oct 14, 1:21*am, nesesu wrote:
On Oct 13, 8:42*pm, " wrote:

How did you locate the manual?

Third item shown when I Googled "Detector Systems model 917-1".

Neil S.

Having trouble posting. I don't know if this is going through.
Neil
Last night I connected about 100 feet of 2 conductor 16AWG. sheilded
cable to the test loop and ran it into the house. The sheild is
grounded on the controller end. The modified coil with three turns and
a 4 ft by 8 ft. perimeter now and a total length of approximately 72
feet is laying in the driveway.With the dip switch sensitivity
combination I found the controller seems to detect a vehicle on the
approach every time now. We're in New Hampshire so the real test will
probably come when the coil is buried and the ground is frozen with
ice and snow on top.
Thank you very much for finding and sending me that manual. The
interesting thing is that although it is indeed for a "917-1", it is
marked 3M. I guess that 3M must have bought out detector Systems and
simply put their own name on the unit. It does appear to be the same
unit as mine though.
In comparing the manual 's coil specifications to mine the manual
calls for a coil consisting of an 18" x 54" loop with 5 or 6 turns of
16AWG. cable. Therefore the total amount of wire in that coil will be
[(18+54) X 2] x 6
[(18+54) x 2] = 144
Then 144 X 6 = 864
854/ 12 = 72ft.
So it seems that although their coil uses more turns of wire, the
total wire length of theirs and my present test coil is the same. In
your opinion, what is the significance of more turns as opposed to
larger perimeter? I'm concerned of course with system reliability and
naturally repeatability. If this thing fails to detect even one time
it will be useless to us. And I certainly won't be digging it up in
January. Would I be better off with building and burying their smaller
coil with more turns or the one I'm trying out now? Thanks, Lenny.