Kaman KDM-8200 - Manual (Page 31)

31
Kaman Precision Products
DISPLACEMENT 0
Calibration
Bipolar
When you use this calibration procedure, output voltage will range from a negative voltage for
Output the first half of your measuring range to a positive output for the second half of the range.
Calibration
Procedure
Use this method when your application is best suited by readouts that represent a positive and
negative deviation from some nominal value, in this case, 0 Vdc. Bipolar calibration also
provides maximum output sensitivity. (An alternate technique is listed after Steps 1-6 that will
provide bipolar output, but not maximum sensitivity).
In a bipolar calibration, clockwise rotation of the Zero control causes output to go more positive;
whereas, clockwise rotation of the Gain control increases gain more negatively in the lower half
of the range and more positively in the upper half. Because of this, you will adjust the Gain
control when the target is closest to the sensor and adjust the Zero control at mid-scale.
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. Position the target using the micrometer fixture or spacers so that the total distance between
the sensor and target is equal to the specified full-scale displacement for that sensor, plus offset.
Adjust the Linearity control (Coarse, then Fine) until the output is equal to the desired full-scale
reading.
3. Position the target so that it is at mid-scale (plus offset) and adjust the Zero control until the
output reads zero.
4. Position the target at its closest point to the sensor (plus offset) and adjust the Gain control
until output reads the desired negative output voltage.
5. Move the target to its farthest point from the sensor. Read the output voltage and 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 (1.000 - .350). If the output reads .800, adjust linearity until
system output reads 1.200 (1.000 + .200).