Kaman KD-2300 - Manual (Page 27)

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Part IV: Calibration KD-2300 Instruction Manual
Offset
Offset is the minimum space or gap between the sensor and target. You
should position your sensor so that the target never enters this area. When
offset has not been considered, linearization of the system can be difficult as
the target enters the offset region. The required offset for a given sensor is
typically 10 to 20% of its full-scale measuring range. See the Sensor
Specifications table in Part 3: EQUIPMENT for sensor offsets.
Offset provides clearance for a moving target, preventing sensor/target
contact. Contact could cause sensor damage and contact errors in
measurement.
If you need to transfer the sensor from a calibration fixture to an application
fixture, maintain the offset initially used in calibration. The maximum
allowable tolerance on repositioning the sensor is -2% to +5% of the offset.
To re-establish offset, note system output when the calibration target is at
minimum displacement (plus offset)— usually 0 Vdc. Remove the sensor
from the calibration fixture and move it to the application fixture. When the
system output equals 0.000 Vdc (or other desired voltage) without adjusting
the controls, the original offset has been re-established.
Sensitivity
Aside from your need to know system sensitivity in order to apply any
meaning to a change in system output, there are several application-specific
variables that you may need to be concerned with:
•
Measuring units. You may want the system output to read directly
in metric units: 100 or 1000 mV/mm.
•
The device you are using to monitor analog output may require a
full scale voltage range other than the factory calibration.
•
Improving signal to noise ratio by 10-15%, thereby improving
system performance. This is especially true when operating with
the first half of a sensor’s measuring range. The Sensor
Specification Table in Part 3: EQUIPMENT list the available
sensors and their recommended output voltage within their full
specified measuring range.
When is the System Fully Calibrated?
Your system is fully calibrated when you complete an iteration of any of the
calibration procedures and find that you did not have to adjust any of the
controls at the zero, mid or full-scale reference points. During calibration,
you will notice that the controls interact with each other. Because of the
interaction, you will have to perform several iterations of a particular
procedure before a system is calibrated. Interaction between the controls
should decrease with subsequent iterations.