Level And Calibration Check (Vibra + Only); Intelligent Data-Reduction Facilities - Profound VIBRA Series Manual

Level and calibration check (VIBRA
4.4
At the start of each measurement the VIBRA
VIBRA +
has been programmed with an on/off time, the system will also perform these checks every time
the system switches on and 'continues' the measurement.
If the geophone has been placed at an angle, a question mark will be displayed on screen of the VIBRA
after the relevant channel. It shall be clear that the measurements for this channel are incorrect. See also
paragraph 4.1.4.
The calibration check is saved with the measurement. This check does not replace the standard
calibration with external testing equipment, but is meant as external check of the measurement quality.
4.5

Intelligent data-reduction facilities

The VIBRA is able to monitor the vibration levels during a period of approximately 4 weeks. The VIBRA is a
fully digital system that samples the actual vibration amplitude level 1024 times per second in three
directions. This means that after a period of 4 weeks the VIBRA has collected over a billion samples.
If all these numbers, together with date and time information, were to be stored in the memory without
using any means of data reduction techniques, the VIBRA would have to be a much larger, inefficient
system. Therefore, the software of the VIBRA is equipped with means to achieve data-reduction without
loosing essential information:
1. Interval: with this option you can define a period in time (between 1 second and 15 minutes) during
which the maximum vibration levels are determined by the VIBRA. Only these peak values, together
with the date and time, will be stored in the internal memory of the VIBRA. Obviously, when a time
interval of only 1 second is defined, the internal memory will be filled much faster compared to a time
interval of 60 seconds or 15 minutes (with the same level of vibration nuisance). The most
appropriate time interval depends on the source of vibration and the type of measurement carried out.
See also paragraph 5.3.1.
2. Save level: this option is used to prevent the data storage of very low, insignificant, vibration levels
into the internal memory. You can define a data save level (threshold value) of say 0.1 mm/s. This
means that as long as the maximum vibration level during a time interval does not exceed this
threshold value, no data will be stored in the internal memory of the VIBRA, confirming that the
maximum vibration level did not exceed the threshold value during that time interval. For you it is not
important to know whether the maximum velocity level during this interval was 0.03 mm/s or 0.08
mm/s. See also paragraph 5.3.2. In the PC software these intervals will be displayed as a line at the
Save Level.
Please note:
For traces the minimum threshold is 0.2 mm/s. If a higher value has been set via the
-
option Save Level, this also applies to the traces.
Concerning the measuring values in accordance with the governing codes (DIN 4150
-
– part 2/ SBR – part B) and as prescribed in these codes the threshold is always 0.1
mm/s (see also appendix II).
- If the measured velocity values within an interval are below the Save Level, the a, f, u
will also not be saved.
+
performs an automatic level and calibration check. If the
Manual Profound VIBRA-series, version 2.00
+
-option only)
+
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