UCM Calibration
FlexPI Product Guide
Page 31
benefit from excluding the high frequencies. However, a sensor cable mounted on a stock cage, or
sheet metal, or steel structure that conduct vibrations quite well would benefit from excluding the
lower frequencies and using the high band.
To verify the sensor’s frequency response, open the Calibrate tool and start a Frequency plot.
Select Auto Scale and use the vertical magnification buttons to fit the frequency response plot in
the window. With the system in a quiescent state with little environmental noise, the response
should be minimal. Any frequency spikes on a quiet system indicate a potential problem
(interference or mounting surface vibrations).
1.
Using the sensor’s default settings, open the Calibrate tool and start recording a Frequency
Response plot.
2.
Look at the Frequency Response while the system is quiet. The Frequency Response should
be low and flat.
3.
Simulate impact attacks along the protected surface using similar levels of force in each test
area.
4.
Review the Frequency Response looking for any frequencies at which the results were
significantly higher or lower than the average response.
5.
If required, adjust the Filter Settings, apply the changes and repeat the tests to obtain a fairly
consistent Frequency Response over the length of the cable.
6.
Once the Frequency response is adequate close the Calibrate tool, save the UCM file, and
download the new settings to the processor.
Step 2 - Calibrating the Gain Settings
The Cable Gain is used to amplify the input signal from the sensor cable before it is processed.
FlexPI has four Cable Gain Settings ranging from 1 (lowest) to 4 (highest).
1.
Using the sensor’s default Gain Setting (2) open the Calibrate tool and start recording a
Magnitude Response plot.
2.
Simulate impact attacks along the protected surface using different levels of force in each test
area (e.g., two heavy impacts, followed by two light impacts, followed by two heavy impacts,
etc.)
Note
In most cases, the frequency created by an impact does not vary
significantly from that of a sustained attack.
Note
If either the protected surface or any nearby equipment resonates at
a frequency within the selectable band (100 to 900 Hz) adjust the
Filter Settings to exclude the resonant frequency.
Note
The response should be similar throughout the zone for impacts of
similar force. If the response increases, or decreases, dramatically in
an area even though the force used is consistent and the mounting
surface conditions are unchanged, there may be a “sweet spot” or a
“low spot” affecting the signal. If this occurs, use the filters to exclude
the affected frequencies.
Note
Although the Cable Gain amplifies the received detection signal it
also amplifies the environmental background noise. Use care when
adjusting the Gain.
