Rockwell Automation Publication 1444-UM001D-EN-P - June 2018 293
Operate the Module Chapter 10
Accelerometers
Accelerometers, and velocity-integrating accelerometers, are designed with a
specified sensitivity, typically ±5 or ±10%, operating frequency range and
direction of sensitivity. The sensitivity is determined based on tests that use a
calibrated input signal at a specific frequency, typically at 80 Hz or 100 Hz, and
does not always measure with the same sensitivity at other frequencies. Sensor
accuracy is also dependent on the direction of the vibration relative to the axis
of the sensor. These sensors are also commonly sensitive to temperature. When
using an accelerometer, make sure that its frequency range is suitable to the
expected signal. Also make sure that the sensor is mounted as close to “in line”
with the shaft center as practical, and that the operating temperature is well
within the rated temperature range of the sensor.
Function Generators
Function generators are commonly used to simulate signals for the testing
instrumentation. These instruments are available in a wide range frequency and
amplitude output capabilities and with varying accuracy specifications.
Accuracy statements such as the following must be considered:
• ±2% of setting 2 mV
Tektronix AFG 3022 Arbitrary / Function Generator
• Typically ±3% ±1 mV at 1 kHz into 50 Ω / 600 Ω
Fluke DDS Function
Generator
• Typical (1 kHz Sine, 0V Offset, >10mVpp, Auto) ± 1% of setting ±
2mVpp (Amplitude into 50 Ω)
Rigol DG4000 Series Function / Arbitrary
Wave f or m G en e r a t o r
Other important considerations include the instruments output impedance,
frequency and amplitude range, DC offset controls, and (perhaps) its ability to
synchronize outputs
(1)
. When using a function generator, make sure that the
signal that the instrument provides to the 1444 monitor is as expected, and its
accuracy is considered in the results of any measurements made.
(1) Some signal generators can lock output channel frequencies together so that they remain synchronized as the output frequency
changes. Other instruments synchronize their outputs when set but do not maintain them synchronized when the output
frequency is then changed.
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