recorded, the MTS control software determines the calibration equation based on
regression analysis between the recorded potentiometer voltage outputs and the
manually measured elevations. This procedure is repeated for each of the linear
actuators.
The Linear Actuator Calibrations panel can be accessed under the
Calibration menu of the MTS control software. These actuators have proven to
have a very linear response, and a linear equation is normally representative of
these data. This linear calibration equation is used to provide feedback for the
elevation of the wave gauge, relative to the still-water level, during the automated
calibration procedure for the wave gauges.
Calibration of wave gauges
Static calibration of the wave gauges is a fully automated procedure and is
conducted remotely using the MTS control software. Experience has shown that
dry wave rods will not provide high-quality calibration data. Therefore, the first
step in the automated calibration procedure is to wet the wave gauges by
temporarily submerging the entire length of each wave gauge. After this is
complete, the linear actuators raise the gauges to locate the still-water level in the
middle of the calibration range for each wave gauge. The gauges are
automatically lowered in preset increments until the still-water level is located at
the upper elevation of the calibration range. The gauge response is recorded at
each elevation. Next, the gauges are automatically raised in preset increments
until the still-water level is located at the lowest elevation of the calibration
range. The gauges are automatically lowered in preset increments until the still-
water level reaches the midpoint of the calibration range for each gauge. This
procedure can be conducted in approximately 30 min, since the 14 wave gauges
are calibrated simultaneously. The wave gauges are generally calibrated prior to
each experiment.
The Wave Gauge Calibration panel, shown in Figure 41, can be accessed
under the Calibration menu of the MTS control software. Both the linear and
quadratic fit options are available in the MTS control software, as shown in the
figure. It is sometimes prudent to use the second-order regression equation
(quadratic) to increase the precision of the wave gauge calibration.
74
Chapter 8
Sensor Calibration, Measurement, and Data Analysis
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