16
4
OPERATING INSTRUCTIONS
4.1
Probe Amplifier Calibration Check
It may be necessary to check and adjust the amplifier calibration for applications which require maximum
accuracy or when the probe and amplifier have been ordered separately. The best results are obtained
when a calibrated micrometer is used as the probe-positioning device. If this is not available, a stand-
alone micrometer such as the MTI KD-CH-IIID calibration stand may be used.
The gain and offset controls on the Accumeasure front panel can be used to calibrate the probe. A slight
tilt of the probe in a fixture also may introduce a gain or offset error that may be eliminated through
calibration.
RECOMMENDED EQUIPMENT
1.
A
Voltmeter
with a minimum resolution of 0.0001VDC and accuracy of ±0.001VDC.
2.
A
Micrometer
with a minimum resolution of 0.05% of the probe range (if available) and accuracy
of ±0.1% of the probe range. (An MTI KD-CH-IIIA Calibration Fixture may be used for this
purpose; refer to the KD-CH-IIIA Operating Instruction Manual to compare the fixture resolution to
the calibration requirements.)
BASIC CALIBRATION
Perform calibration by adjusting the front-panel GAIN and OFFSET controls. Offset is adjusted while the
probe is at 10% of range. Gain is adjusted at 100% of range. Use the following procedure:
1.
Set the voltmeter to monitor the output of the amplifier.
2.
With the unit turned off, adjust the probe so it is lightly touching the target.
3.
Zero the micrometer and then move it back to 10% of the intended range. Turn the unit back on.
4.
Press in the OFFSET switch on the front panel of the AS-9000 and adjust the front-panel control
for OFFSET until the output reads 1.000 VDC.
5.
Move the micrometer to 100% of range and adjust the GAIN control until the output reads 10.000
VDC.
6.
Readjust
the
micrometer
to
10%
of
range
and
recheck
the
10%
point
(1.000 V). Readjust OFFSET if necessary, and recheck the 100% limit.
7.
Repeat steps 5 and 6 until the voltage at 10% of range is 1.000 ±0.001 VDC and the voltage at
100% of range is 10.000 ±0.001 VDC.
8.
Verify several points between the minimum and maximum limits.
If this procedure does not produce the desired system accuracy, more elaborate calibrations such as
linearizing the output may be accomplished by readjusting internal potentiometers. These adjustments
must be made at the factory or by a qualified MTI representative.
WARNING
Under no circumstances should you adjust pots on the internal boards. These pots control the CMRR (common
mode rejection ratio), balance, and other amplifier parameters and should only be adjusted at the factory.
Opening the product voids any warranty or factory calibration certification.
Summary of Contents for AccuMeasure 9000
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