Electronic compass

[Roy Hammond]

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)

 

[TimPerry]

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)

check the battery or supply voltage when the light is on

 

[Jerry G.]

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.

 

[Kim]

Why don't you tear out the electroluminescent circuit (assuming that is
possible) and replace it with a good ol-fashioned LED illuminating system
(assuming the light will pass through and illuminate the display).
No way that can upset the compass.
Kim

 

[Roy Hammond]

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)