Kaman KD-2300 - Manual (Page 32)

KD-2300 Instruction Manual Part IV: Calibration
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VDC
offset
DISPLACEMENT
Bipolar Output Calibration
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 - 0.350). If the output reads 0.800, adjust linearity until system
output reads 1.200 (1.000 + 0.200).