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VibrationVIEW Help 197
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will abort. These are safety limits used to protect from overdriving your shaker. We recommend
setting these to about 150% of the values expected while running the test. Refer to the calculations on
the
Playback tab to see what the requirements of the demand waveform are.
Note: The system-wide acceleration limits also apply to the test. The actual limit used will be the
smaller of the limit configured here and the system limit configured in the Configuration..Limits
dialog box. The Random Acceleration limit is used as the absolute maximum RMS limit, and the
smaller of the Sine and Shock Acceleration limits is used as the absolute maximum Peak limit.
The Output Threshold and Starting Max System Gain parameters are safety limits that define an output
voltage limit as a function of the measured RMS acceleration level. When starting a test, the output
voltage will be limited to:
(Output Voltage) <= (Output Threshold) + (Starting Max System Gain)*(Measured RMS Acceleration)
If you start a test without an accelerometer connected, these settings will limit the maximum output
allowed and the controller will abort the test. When an accelerometer is connected, the output voltage
will be allowed to increase as the measured RMS acceleration level from the accelerometer increases.
The output threshold parameter is typically 0.005 Volts for an Electro-Dynamic shaker and 0.050 Volts
for a Servo-Hydraulic shaker. The Starting Max System Gain parameter depends on the shaker
system and the amplifier gain setting. To determine this value, start the test and after the output
reaches the demand amplitude note both the "Volts rms" and the "Demand G RMS" readings in the
FDR Control Center. Set the Starting Max System Gain parameter to approximately:
Starting Max System Gain = 4 x (Volts rms) / (Demand G RMS)
To disable this limit, set the Starting Max System Gain parameter to a large number (1000 V/G), or set
the Output Threshold parameter to 10 Volts.
The Running Max System Gain parameter is another safety limit that limits the output voltage as a
function of the measured RMS acceleration while the test is running. This value should typically be set
to double the V/G level required by your system. To determine your required V/G setting, set the
Running Max System Gain parameter to a high level (e.g. 1000 V/G), click the "Apply" button, run the
test and note the RMS output voltage level required by the test, as indicated in the FDR Control Center.
Divide this voltage level by the Demand G RMS level (also shown in the FDR Control Center) and
multiply by 2.
The Max Output parameter defines the maximum RMS output voltage allowed from the controller. If
the drive signal output ever exceeds this value, the test will abort. To determine an appropriate max
output setting, run the test and look at the "Volts rms" reading displayed on the FDR Control Center.
Multiply that value by 1.5 (to give a 50% cushion) to get an appropriate Max Output setting.
4.5.5 Filter tab
Field Data Replicator Define Filter tab
Click the "Filter" tab on the Test..Edit Test Settings dialog to display this page.
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