ARL EL-235 Tri-axial Ground Vibration Logger

These are the help screens from the supplied software.

Note: When setting this logger up you must consider what type of readings you require. Do you need acceleration, vibration, or displacement? This logger will only measure one of these at a time and you CANNOT convert logged acceleration measurements to displacement or velocity. So make sure you select the appropriate measurement type. Generally for ground vibration Peak Particle Velocity (PPV) is required. So set the filtering to velocity and the filtering to peak.

Filtering/Detection

There are 2 types of detection available in the EL-235. These are:

There are 3 types of filtering available in the EL-235. These are:

Any combination of detection and filtering is available.

Vibration Events Captured
Events data is data which is captured by the EL-235 whenever vibration levels exceed a pre-determined threshold. This threshold is set by the user at the start of a logging session.

Events data includes:

The energy parameter is made available to give an indication of the energy content of a vibration event. The effect of vibration on a structure is not only linked to the maximum amplitude of a vibration event, the duration of the event is also a factor. This is illustrated below.

The length of time between when the vibration level exceeded the threshold to the maximum level recorded during the event. Values for each individual axis are given in the events data. An example for the X axis is shown below.

Events data is stored in the EL-235 along with the statistical data (Statistical data is vibration data which is calculated at the end of each regular statistical interval). but is extracted and stored in a separate file on your computers disk.

Time Capture
This option accesses the time capture facilities of the EL-235. A vibration event of up to 2.05 seconds in length may be sampled by the EL-235. The event's amplitude and frequency response data is stored as a .CSV file which may be graphically displayed using the < View Data > option in the Analysis menu.

To Perform a Time Capture:
(i) Select the channel (X, Y, or Z axis) that you wish to record by clicking on the appropriate option button in the "Channel" frame

(ii) Set the Pre-Trigger Time
The pre-trigger time determines the length of the delay between the time that the vibration level exceeds the set threshold and the time when the logger starts a time capture.

(iii) Set the Trigger Threshold
The trigger threshold is the level of vibration which will cause the EL-235 to commence a time capture operation. This is shown graphically in the figure below.

(iv) Type in a measurement name for this time capture
(v) When ready to capture the event, click on the < Start Measurement > button

The logger will now wait for the incoming vibration level to exceed the trigger threshold for the time period set by Pre-Trigger Time. When these conditions are satisfied, the logger will commence the time capture.

When the time capture is complete you will be asked for a name to give to the .CSV file where the data will be stored. Enter any DOS/Windows compatible filename with a CSV extension (e.g. timecap1.csv), and the data will be saved.

Track Events
This option opens a window which shows a real-time events display. As each event is registered by the EL-235, its parameters are displayed in the appropriate boxes in the window. Parameters displayed are:

(i) Event Status


The above diagram shows the event length for an event captured on the X axis and a separation time of 5 seconds.

(ii) Maximum Values Displays the maximum level of vibration attained during an event. Values for each individual axis are displayed. An example for the x-axis is shown graphically below.


For

(iii) Delay To Max The length of time between when the vibration level exceeded the threshold to the maximum level recorded during the event. Values for each individual axis are given in the events data. An example for the X axis is shown below.


For

Statistical Levels These are given in the X, Y, and Z directions as well as the vector value

• LMax - The Maximum level in the interval
• L0.1 - The vibration level exceeded for 0.1% of the time interval
• L1 - The vibration level exceeded for 0.1% of the time interval
• LA10 - The noise level exceed for 10% of the 15 minute interval. This is commonly referred to as the average maximum level
• LA90 - The noise level exceeded for 90% of the sample period. This vibration level is described as the average minimum background vibration sound level (in the absence of the source under consideration), or simply the background level
• LAeq - The equivalent vibration level (basically the average noise level). It is defined as the steady vibration level that contains the same amount of energy as the corresponding time-varying vibration

Additional Resources

User Manual (pdf)