Kaman KD-5100 - Manual (Page 19)

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11. SENSOR INSTALLATION GUIDELINES AND
PROCEDURES
11-1. The electrical nulling procedure.
Note: This installation procedure is the preferred method. Though both sensors may be
positioned mechanically, this can cause a cumulative error. By electrically positioning
the second sensor of a pair using system output, any existing error is self-canceling.
11-2. Install the sensors so that only the target interacts with the sensor’s field. This means no
conductive material other than the target within a circle around the sensor that is three times the
sensor’s diameter. The sensor field radiates in all directions. (Figure 12) and excessive back
loading can also be a problem.
CAUTION: Be sure not to damage the sensor coil during this procedure
Figure 12 Sensor Field
11-2a. This procedure assumes the electronics are installed in the application fixture.
11-2b. The sensor coil is mounted at the face of both sensors. For purposes of
mechanical nulling, measure distance from the sensor face. For electrical nulling the null
gap is referenced to the electrical centerline, which is one half of the coil depth (½D,
Figure 9).
11-3. Sensor position relative to the target is critical. Make sure the target is in the null position.
Install the first sensor of a pair (start with S3) in the application fixture. Using a dimensional
standard, precisely locate the sensor 15 mils (±0.2 mils) for the 15N sensor, or 20 mils (±0.2
mils) for the 20N sensor from the target. Secure the sensor and recheck its position.
11-4. Now install the second sensor of the pair (S1) in the fixture and position it to within a few
mils of the required null gap. Connect the Power/Signal line to J5 and apply power to the
system. Use the output from the system as a guide in the final positioning of this sensor
(electrical nulling). Slowly move the second sensor toward or away from the target as necessary