Electronic Compass Investigation

I purchased an electronic compass for possible integration
into the next BEAR equipment package to show in which direction a camera is pointed when photos are taken.

I purchased this compass in the auto dept of Canadian Tire for $39.99 Canadian, but the same unit was found on the web under various names at many places for $39 to $59 USD.

Opening the unit without destroying the plastic case wasn't easy as GLUE was used in addition to a number of screws.

For information on the operation of the magnetic field sensor used in this unit, refer to the following manufactures literature:

KMZ52 Data Sheet

KMZ52 App Note

General Magnetic Field Sensors Data Sheet

Earth Field Sensors

The I.C. is mounted on a small circuit board which is at an angle to the main circuit board so as to be nearly level when used in an auto and the display is tilted at a typical viewing angle. Accuracy depends on the I.C. being "flat" with respect to the earths surface and this factor was found too critical to make this type of compass useful for my application .
"Tilt" error can be overcome by using a compass with 3 axis, rather then 2 axis sensing, but such units are much more expensive.

The LCD display interfaces with the long multi-conductor strip along the bottom of the photo. The microprocessor chip that interprets data from the KMZ52 and functions as the LCD controller is embedded in the blob of black epoxy.

The tiny silver cylinder with 2 leads is the microprocessor crystal. One of the two I.C.'s is a quad op-amp used to amplify the small output voltages from the KMZ52 circuit.