Kaman KD-2300 - Manual (Page 31)

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Part IV: Calibration KD-2300 Instruction Manual
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 (offset). With
curved targets, decreasing offset will improve linearity; with flat targets,
increasing offset slightly will improve linearity. In either case, never allow
the target to strike the sensor face.
2. a. 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. See the Sensor Specification
Table in Part 3: EQUIPMENT for standard offsets.
b. To calibrate for a specific sensitivity, follow the procedures in Step 2a, then
adjust the Gain control so that system output equals your desired new full-
scale output voltage.
3. Position the target to zero displacement (plus offset). Adjust the Zero control
until the output voltage reads 0 Vdc.
4. Position the target at mid-scale plus offset and adjust the Gain control until
the output voltage reads the desired mid-scale value. For example, assuming
10mV/mil sensitivity, and your full-scale voltage is 1 Vdc at 100 mils, then the
system output at mid-scale should read 0.5 Vdc at 50 mils.
5. Reposition the target at full-scale displacement, plus offset. 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 0.650, or
1.000- 0.350. If the output reads 0.800, adjust linearity until system output
reads 1.200, or 1.00 + 0.200.
6. Repeat Steps 3 through 5 as many times as necessary until the desired output
voltage at each point is reached. No further adjustment of the Zero, Gain and
Linearity controls will be needed when proper calibration is obtained.
Bipolar Output Calibration Procedure
When you use this calibration procedure, output voltage will range from a
negative voltage for the first half of your measuring range to a positive output for
the second half of the range.