Kaman digiVIT - Manual (Page 9)

www.kamansensors.com PART NO: 860525-001
Last Revised 9/16/2013
- 9 -
4.4.2 6 Pt. Poly Cal
The 6 point polynomial cal fits a 5th order polynomial through the data points to linearize the
sensor output. In most cases this method works very well though there can be exceptions.
The sensor needs to be position at MAX distance from the sensor face (i.e. full scale) so that it
can optimize for a given sensor. After that the sensor needs to be position at offset (MIN) and
then at 20%, 40%, 60%, 80%, and 100% of the range to complete the calibration.
Note: Any previous temperature compensation calibration will be voided when a 6 Pt. calibration
is performed.
4.4.3 21 Pt. Pcws Cal
This calibration will result in the best performance. It is a 21 point piecewise linearization
method. This option works best if the curve is too oddly shaped for a polynomial to fit well.
The sensor needs to be positioned at the MAX distance from the sensor face (i.e. full scale) so
that it can optimize for a given sensor. After that, it needs to be positioned in 5% of the range
increments from 0-100%.
Note: Any previous temperature compensation calibration will be voided when a 21 Pt.
calibration is performed.
4.5 Temperature Compensation
The digiVIT optimizes the sensor for temperature stability and linearity using proprietary
algorithms. However, even with this optimization, some residual error exists due to
temperature. Temperature stability can generally be improved by a factor of 5-10 using
additional steps to temperature compensate the unit. To perform temperature compensation,
data from 2 different displacements with 2 different temperatures must be acquired by the unit.
The actual displacement does not matter, but the recommended displacements are
aproximately10% and 90% of the calibrated range. If the best temperature coefficient is desired
at a particular displacement, that displacement should be chosen as one of the displacements
used. The temperature compensation algorithm will have the smallest temperature error at that
displacement 1 and 2 when the calibration is completed. The 4 required points are:
D1T1 (Displacement 1, Temperature 1)
D1T2 (Displacement 1, Temperature 2)
D2T1 (Displacement 2, Temperature 1)
D2T2 (Displacement 2, Temperature 2)
The temperature compensation calibration menu controls the order of the 4 points.