Kaman KD-5100 - Manual (Page 12)

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7. FIXTURING
7-1. The user provides fixturing for the KD-5100 electronics and sensors. The following
information establishes fixturing requirements for optimum system performance. The quality of
the measurement is both a function of Kaman’s system and your Fixturing.
7-2. Both the sensor and target fixturing must be structurally sound and repeatable.
7-3. Factors that degrade performance are:
7-3a. Unequal Loading
This refers to an unequal amount of conductive material within the field of one sensor of
a pair as opposed to another (the sensor’s field is approximately three times its diameter).
Unequal loading causes asymmetrical output from the sensor, which induces non-
linearity in the system output. Ideally, no conductive material other than the target
should be in the sensor’s field. Some loading may be acceptable if it is equal and the
sensors are calibrated in place. Even then, sensor loading may cause non-linearity. If
unable to calibrate – loading is too great.
7-3b. Unequal Displacement
For targets using a pivot point mount (examples, Figures 3 & 4) the system should “see”
equal displacement: i.e., the pivot point of the target is perfectly centered between the
sensors. If the pivot point is a fraction of a mil off it can introduce non-linearity into the
system.
7-4. Other pivot point requirements:
7-4a. The pivot point must be a common line between the centerline of a pair of sensors.
7-4b. The axis of tilt must be a perpendicular bisector of a line between the centerlines of
a sensor pair.
7-4c. The pivot point must be positioned on the target so as not to introduce a translation
error. This error, a function of angle, is caused by slight changes in the effective null gap
as the target moves about the pivot. This results in non-linearity.
7-4d. The pivot point must not change or move with time.
7-5. Sensor mounting considerations:
7-5a. The sensors must be securely clamped. Sensor dimensions are shown in Figures 7
and 8.