Kaman KDM-8200 - Manual (Page 27)

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Kaman Precision Products
Calibration
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 lists the available sensors and their recommended
output voltage within their full specified measuring range.
When is the
Your system is fully calibrated when you complete an iteration of any of the calibration
System Fully procedures and find that you did not have to adjust any of the controls at the zero, mid or full-
Calibrated?
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
each iteration.
Calibration
You will need to calibrate each measuring channel in your system using the Zero, Gain, and
Controls Linearity (Coarse and Fine) potentiometers located on the control end of the module. The
controls rotate both clockwise and counterclockwise through the use of a small screwdriver or the
supplied calibration tool.
A description of each calibration control follows:
Clockwise rotation of calibration controls causes the analog output to go more positive;
counterclockwise causes more negative output. If you turn a potentiometer in the same direction
(clockwise / counterclockwise) until you see no change in system output, you have reached a
limit of that particular control. If this occurs, your options are: 1) change the gain by changing
the gain jumper (APPENDIX B), 2) check for excess loading around the sensor, or 3) make sure
that your target size and material are appropriate (Part 3: EQUIPMENT).
Test Points
The test points located on the front panel can be used to test the output voltages with a handheld
voltmeter. The testpoint labeled ‘TP1’ is the demodulator output of the system. In the standard
8200 systems, ‘TP1’, should never go below zero volts (the log amp will attempt to take the log
of a negative number). The output of ‘TP1’ is negatively sloped and generally ranges from 0.050
volts at Full Scale to 6 volts at the system offset. These values vary depending on the measuring
range and sensor. There could be a negative value at the offset only if the log amp has been
removed or bypassed. The system zero and gain controls have no effect on this output. The test
point labeled ‘OUT’ is the same as the output on the back of the module (C14 and A14). The test
point labeled ‘GND’ is the same ground as the ground pins on the back of the module.