Kaman KDM-8200 - Manual (Page 33)

33
Kaman Precision Products
Calibration
High
As you perform a high accuracy band calibration, keep in mind that the smaller the
Accuracy calibrated span the more interactive the controls will become. More interaction means
Band more iterations before your system is fully calibrated.
Calibration
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, ensuring that when the target is at its
closest point to the sensor, there is a gap (see the Sensor Specifications table in Part 3:
EQUIPMENT, page 24 for offsets). With curved targets, decreasing offset will improve linearity;
for flat targets, increasing offset slightly will improve linearity. In either case, never allow the
target to strike the sensor face.
2. Define the reduced measurement span you will use.
3. Position the target so that it is at the end of your defined span, plus offset. Adjust the
Linearity Control (Coarse then Fine) until the output reads the desired maximum voltage.
4. Position the target at the beginning of your defined span (plus offset) and adjust the Zero
control to read the desired voltage at that point. The desired voltage does not have to be zero.
5. Position the target at the mid-point between the end points of the desired span. Adjust the
Gain control until the output reads the desired voltage.
6. Reposition the target so that it is at the far end of the span relative to the sensor. Note the
difference between the actual reading and the desired reading. Adjust the linearity control
(Coarse, then Fine) until the output reads the desired voltage level, then continue past the desired
reading by an amount equal to the first difference you noted. This technique is called 100%
oversetting and is used to reduce the number of iterations needed to calibrate the system. For
example, if the output reads 1.350 volts and the desired reading is 1.000, adjust the Linearity
control until the output reads .650, or, 1.000-.350. If the output reads .800, adjust linearity until
system output reads 1.200, or, 1.000+.200.
7. Repeat Steps 3 through 6 as many times as necessary until you reach the desired output
voltage at each point. No further adjustment of the Zero, Gain and Linearity controls will be
needed when proper calibration is attained.