Kaman KDM-8206 - Manual (Page 16)

4.3.5 High Accuracy Band Voltage Calibration
DISPLACEMENT
offset
VDC
0
High Accuracy Band
Calibration
CALIBRATED
RANGE
This procedure is used to monitor changes in position that are less than the specified linear
measuring range of the sensor, or for increased accuracy over a smaller range when not concerned
about high accuracy outside of that range.
The high accuracy band procedure maximizes the linearity of output within a calibrated span. The
sensor installed in your system has a specified linear measuring range that defines system
performance characteristics, such as linearity, resolution and long-term stability.
Maximum linearity is centered on the mid-point of the sensor’s specified maximum linearity measuring
range anywhere between 25-75% of full-scale. For example, if you have a system with a 40 mil
specified range; its most linear region will be between 10 and 30 mils.
While decreasing the linear measuring range of your system, it will improve system performance;
conversely, increasing measuring range will degrade performance. Depending upon measurement
objectives, either can be used.
As you perform a high accuracy band calibration, keep in mind that the smaller the calibrated span
the more interactive the controls will become. More interaction means more iteration before the
system is fully calibrated.
When the desired span is below 20% of specified linear measuring range, the additional improvement
in linearity is generally not worth the trouble caused by control interaction.
1. Install the sensor in the calibration or application fixture at the offset distance.
2. Define the reduced measurement span you will use.
3. Position the target so that it is at the maximum displacement of your defined span, plus
offset. Adjust the MAX controls until the output reads the desired maximum voltage.
4. Reposition the target at the minimum displacement of your defined span (plus offset) and
adjust the MIN controls to read the desired voltage at that point. The desired voltage
does not have to be zero.
5. Reposition the target at the mid-point between the end points of the desired span. Adjust
the MID controls until the output reads half the value between minimum and maximum
output.
6. Reposition the target so that it is at the maximum displacement of the span relative to the
sensor. Note the difference between the actual reading and the desired reading. Adjust
the MAX controls until the output reads the desired voltage level, then continue past the
desired reading by an amount equal to the first difference you noted.
7. Repeat Steps 3 through 6 as many times as necessary until you reach the desired output
voltage at each point without additional adjustment.
Kaman Precision Products PART NO: 860516-001
www.kamansensors.com Last Revised: 6/20/2011
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