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Using System Check to Verify Input Sensitivities & Displacement

March 29, 2018

VibrationVIEW’s System Check can be used to verify sensor input sensitivities and shaker displacement prior to running a test.

Determine Unknown Sensitivity of a Sensor

With a Reference Accelerometer

The goal is to enter a known sensitivity and guess an unknown sensitivity. If a sine wave produces the same response on both channels, the guess is correct*.

1. Mount both accelerometers on shaker head
2. Go to menus item Configuration > System Limits
Ensure system limits are configured correctly
3. Go to menu item Configuration > Inputs
Enter known sensitivities of reference accelerometer on Channel 1 (meaning any accelerometer with known sensitivity)
Enter a sensitivity value (start low!) of accelerometer with unknown sensitivity on Channel 2
IMPORTANT: If in doubt about sensitivity, always start low! If the accelerometer has low sensitivity and you enter a high sensitivity, you will receive much higher acceleration values on this channel. (i.e.: If accelerometer is 10 mV/g and you start out by guessing 100mV/g, then this channel will read 10 times the true acceleration – you are guessing the sensitivity is 10 times higher than actual. By starting low and working your way up, you can avoid any potentially dangerous situations).
4. Choose Test Type > System Check
5. Set a frequency value: default is 30Hz (works well for ED shakers)
6. Set a displacement value: default is 0.1″ (works well for ED shakers)
7. Run System Check test
8. If Sine wave response matches on both channels, the guessed sensitivity on Channel 2 is fairly accurate
9. If Sine wave response does not match on both channels, gradually increase the sensitivity guess on Channel 2 until both channels produce the same result

*Results are not precise measurements

Without Any Reference Accelerometer

The goal is to enter an unknown sensitivity and use displacement to determine the accuracy of the guess. A sensitivity value close to the actual sensitivity of the shaker should result in the shaker’s visual displacement matching the software’s required displacement*.

1. Mount the accelerometer with unknown sensitivity on shaker head
2. Place displacement wedge sticker on shaker
3. Go to menu item Configuration…System Limits
Ensure system limits are configured correctly
4. Go to menu item Configuration…Inputs
Enter a sensitivity value (start low!) of accelerometer with unknown sensitivity on Channel 1.
IMPORTANT: If in doubt about sensitivity, always start low!  If the accelerometer has low sensitivity and you enter a high sensitivity, you will receive much higher acceleration values on this channel. (i.e.: If accelerometer is 10mV/g and you start out by guessing 100mV/g, then this channel will read 10 times the true acceleration – you are guessing the sensitivity is 10 times higher than it actually is.  By starting low and working your way up, you can avoid any potential dangerous situations).
5. Choose Test Type…System Check
6. Set a frequency value: default is 30Hz (works well for ED shakers)
7. Set a displacement value: default is 0.1″ (works well for ED shakers)
This is verifiable, visually, with a displacement wedge
8. Walk over to the shaker and visually verify displacement
If displacement wedge shows the same displacement value in the software, the sensitivity guess was fairly accurate
If displacement wedge shows a lower displacement value than what is shown in the software, gradually increase the guess until the displacement values match

*Results are not precise measurements

Compare Two or More Sensors

The goal is to ensure all sensors are functioning properly

1. Mount sensors on shaker head
2. Go to menu item Configuration > System Limits
3. Ensure system limits are configured correctly
4. Go to menu item Configuration > Inputs
Enter sensitivity values of all sensors
5. Choose Test Type…System Check
6. Set a frequency value: default is 30Hz (works well for ED shakers)
7. Set a displacement value: default is 0.1″ (works well for ED shakers)
8. Run System Check test
If sine wave matches on all channels, all sensors are functioning properly
If sine wave doesn’t match on one or more channels, re-verify input sensitivities or repair malfunctioning sensor

Visually Verify Displacement

The goal is to verify that the shaker is operating as expected

1. Mount control sensor on shaker head
2. Place displacement wedge sticker on shaker
3. Go to menu item Configuration…System Limits
Ensure system limits are configured correctly
4. Go to menu item Configuration…Inputs
Enter sensitivity value of sensor
5. Choose Test Type…System Check
6. Set a frequency value: default is 30Hz (works well for ED shakers)
7. Set a displacement value: default is 0.1″ (works well for ED shakers)
This is verifiable visually with a displacement wedge
8. Run System Check test
9. Walk over to the shaker and visually verify displacement to determine that it is operating as expected