Rail Crossing Applications
Loop Detector Application Notes SLD4
667/HQ/45200/101
21
Figure 9 : Loop Sensitivity Settings (%DL/L and [Hz] are site dependent)
9.
For each loop in question, set the fixed value for the sensitivity using the DIP switch
on the front panel in accordance with the frequency values recorded above. Select
the higher value in borderline cases. In the example, the threshold value recorded
was 19Hz so the user should select elect 23 Hz from the table in Figure 9
Note
The threshold value selected should not be smaller than the values recorded for background
noise.
Figure 10 : New Vehicle Profile with New Threshold
10.
The MODE LED double flashes / flashes as the same speed as the POWER LED
11.
Push the reset button for approximately 3 seconds until the POWER LED is perma-
nently illuminated
5.4.
Confirmation of Performance
Drive over each loop in a car at least two times and record the signals.
Test Confirmation Criteria:
•
If required, adjust the sensitivity from the table and drive over the loop again.
Then record the selected value
•
The loop must remain occupied when there is a car continuously present on the loop.
•
The loop may not become spontaneously occupied (false positive) without a road ve-
hicle being present.
•
It may be considered reasonable that the loop ‘detects’ whilst a train is passing, how-
ever the loop should not detect once the train has passed.
