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13. Quality Evaluation and Replacement of Sensor/Magnetic
Tool used
The sensors/magnetic used in Casio watches equipped with an electronic compass consist of mag-
netic resistance (MR) devices in which the resistance value changes in response to the effects of the
earth's magnetism.
These devices combine a total of four magnetic resistors, with two in the direction of the X axis and
two in the direction of the Y axis.
In addition, a bias magnetic field is generated within the device as well in order to detect the direction
of weak magnetic fields such as those produced by the earth's magnetism.
The effects of the earth's magnetism and this bias magnetic field produce a change in the resistance
values of the four magnetic resistors.
That change is then detected as a potential difference (voltage) at the output terminal to determine
direction.
13-1 When a Watch Does Not Indicate Directions Correctly
Since a device is used in which resistance values change according to the effects of the earth's
magnetism as described above, when the watch does not indicate the correct direction, the following
three types of causes should be considered other than a malfunction in the sensor/magnetic itself.
1) Measurements are made nearby or inside objects that block the earth's magnetism such as iron
desks or lockers, inside a vehicle or indoors (especially reinforced concrete buildings).
2) Measurements are made in close proximity to objects that generate their own powerful magnetic
field causing distortion of the earth's magnetism, such as magnetic necklaces, high-voltage power
lines, aerial lines and electrical appliances (including televisions, personal computers and speak-
ers).
3) The watch itself has become magnetized for reasons such as placing the watch near any of the
objects described in 2) above.
In the case of 1) or 2), direction will be determined correctly if measurement is performed in a
different location. In the case of 3) however, “bidirectional calibration” and “northerly calibra-
tion” should be performed to demagnetize the watch.
Correction is performed as described in each instruction manual or operation chart in the service
manual.
13-2 Quality Evaluation of Sensors/Magnetic
When the watch still does not measure direction correctly even when the above corrections have been
made or when sensor error is displayed or direction is not displayed, the sensor/magnetic may have a
malfunction. Evaluation of the quality of sensor/magnetic is performed by measuring the resistance
value between the terminals of the sensor.
The resistance values between each terminal are as shown in next page.
NO.
Code No.
Tool name
1
1901 9672 Precision screwdriver set
2
1901 9523 Precision tweezers
3
1904 5277 Multimeter
4-1 1704 1667 Soldering iron (110 V/117 V)
4-2 1904 1668 Soldering iron (220 V)
5
1901 9868 Solder wick
6
1901 9401 Solder
7
1901 9519 Blower brush
Summary of Contents for ABX-68B
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