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 the unknown sensitivity of a sensor
Compare two or more sensors
Visually verify displacement using a displacement wedge

Determine the 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.*

Mount both accelerometers on the shaker head.
Select Configuration > Limits. Ensure that the system limits are configured correctly.

Select the Inputs tab.

Enter known sensitivities of the reference accelerometer for Channel 1 (any accelerometer with a known sensitivity).
Enter a sensitivity value of the accelerometer with unknown sensitivity for Channel 2.

If in doubt about the 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. For example, if the accelerometer is 10 mV/g and your first guess is 100 mV/g, then the channel will read 10 times the true acceleration. Your guess is 10 times higher than the actual value. By starting low and working up, you can avoid any potentially dangerous situations.

Select Test > Test Type > System Check.
Set a frequency value; the default is 30 Hz (works well for ED shakers).
Set a displacement value; the default is 0.1″ (works well for ED shakers).
Run the test.

If the sine wave response matches on both channels, the guessed sensitivity on Channel 2 is fairly accurate.
If the 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 A 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.*

Mount the accelerometer with unknown sensitivity on the shaker head
Place a displacement wedge sticker on the shaker
Select Configuration > Limits. Ensure that the system limits are configured correctly.

Select Inputs. Enter the sensitivity value for the accelerometer with unknown sensitivity on Channel 1.

If in doubt about the 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. For example, if the accelerometer is 10 mV/g and your first guess is 100mV/g, then the channel will read 10 times the true acceleration. Your guess is 10 times higher than the actual value. By starting low and working up, you can avoid any potentially dangerous situations.

Select Test > Test Type> System Check.
Set a frequency value; the default is 30 Hz (works well for ED shakers).
Set a displacement value; the default is 0.1″ (works well for ED shakers).
Walk to the shaker and visually verify the displacement.

If the displacement wedge shows the same displacement value in the software, the sensitivity guess was fairly accurate.
If the 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

Ensure all sensors are functioning properly.

Mount sensors on the shaker head.
Select Configuration > Limits. Ensure the system limits are configured correctly.

Select Inputs. Enter the sensitivity values for all sensors.

Select Test > Test Type > System Check.

Set a frequency value; the default is 30 Hz (works well for ED shakers).
Set a displacement value; the default is 0.1″ (works well for ED shakers).

Run the test

If the sine wave matches on all channels, all sensors are functioning properly.
If the sine wave doesn’t match on one or more channels, re-verify the input sensitivities or repair the malfunctioning sensor.

Visually Verify Displacement

Verify that the shaker is operating as expected.

Mount the control sensor on the shaker head.
Place the displacement wedge sticker on the shaker.
Select Configuration > Limits. Ensure that the system limits are configured correctly.

Select Inputs. Enter the sensitivity value of the sensor.

Select Test > Test Type > System Check.

Set a frequency value; the default is 30 Hz (works well for ED shakers).
Set a displacement value; the default is 0.1″ (works well for ED shakers).

Run the test.
Walk to the shaker and visually verify the displacement to determine that it is operating as expected.