400
300
200
100
0
-100
-200
-300
-400
-500
-600
-12.5 -10.0 -7.5 -5.0 -2.5 0.0 2.5
5.0
7.5 10.0 12.5
Voltage (volts)
Figure 43. Relationship between the output voltage range from the ADVs and
the range of the A/D converters with respect to engineering units
Scaling the analog output signals from voltage to velocity is accomplished by
using the Existing Sensors panel, shown in Figure 44, which is located under the
scaling as shown in this manner.
Additionally, it is possible for the
voltage level measured with the MTS
control and data acquisition system to
differ slightly than the voltage output from
the ADVs. These differences are most
likely caused by temperature fluctuations
that cause variability in the impedance of
the 130-m long analog cables. Therefore,
the analog output signals from the ADVs
are calibrated on a regular basis to
compensate for these small variations.
Calibration is performed by commands in
the ADV software that force each ADV
Figure 44. Existing sensors panel in the MTS
system to output a precise and constant
control software is used to scale
analog voltage of either 0.000 or 5.000 V.
the analog output signals from
The water in the facility does not require
voltage into engineering units
motionless to conduct this procedure. The
(Permission to reprint granted by
MTS Systems Corp.)
first step in the process is to force a given
ADV system to output 0.000 V. If the
analog-to-digital converter does not read exactly 0.000 volts, the value of the
offset is adjusted using the A/D-D/A Converters panel as shown in Figure 45.
79
Chapter 8
Sensor Calibration, Measurement, and Data Analysis
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