Checking the battery volts sounds like a good idea! Can't think why I didn't
think of that myself! Especially since an extra battery (CR2032 lithium coin
cell) was included (added) to the blister packed unit, apparently after the
unit package had been completed. Will rescue the compass from the car
tomorrow and see if low battery power is the problem...
[The compass calibration procedure is supposed to compensate for both
internal and external interfering magnetic fields.]
Thanks all...
-Roy-
(Surrey, England)
"Jerry G." wrote in message
...
The only thing you can do is to make sure that the battery supply is
staying level when the light is working. It is also possible that this
device is very cheaply designed, and there was not proper consideration
for the magnetic field that the light wiring would be causing when there
is current flow through it.

I would have no idea in something like the device that you have, where you
can have effective magnetic shielding. If you start with magnetic
shielding, I am very sure you will have problems to take readings with it.

I have used electronic compasses that are very high end. They have
incorporated in to their design, compensation for the internal electrical
operation.

--

Jerry G.
======


"Roy Hammond" wrote in message
...
Recently I purchased a new fluxgate compass (trademarked Williams F1 made
in China) very neat, and cheap (£9.99). It works fine and calibrates
well, but when the LCD blue glow backlight button is pressed, it
lights-up for the requisite 60 seconds or so, BUT the compass reading
goes all over the place - quite unusable! I guess that was why the
compasses were selling so cheaply in the store. Only for use in
daylight!
The backlight is electrolumninescent and obviously is generating a
spurious magnetic field. Has anybody any experience or ideas on how this
problem can be overcome?
-Roy-
(Surrey, England)