301UM0031_01
TD136 Enhanced Vehicle Detector User Manual
Page: 10 of 29
3.2.2 Sensitivity
The sensitivity of the detector allows the detector to be selective as to the change of inductance
necessary to produce a detect. There are four sensitivity selections and are set as follows: -
SW4
SW3
Off
Off
High
On
Off
Medium-High
Off
On
Medium-Low
On
On
Low
3.2.3 Presence Time
The presence time is a mode, which allows the detector to have a presence time of no longer than the
time set. The mode is selected by switches No.5 and 6 on the front of the enclosure and is as follows: -
SW6
SW5
Off
Off
∞
no fixed time
On
Off
40 min
Off
On
4 min
On
On
1 sec
The presence time as shown above may be altered according to the requirements.
The 1 second setting will give a pulse on detection of a vehicle with a duration of 1 second. The
detector will immediately re-adjust to the normal operating point and will give another detect in the
event of a further change in the loop inductance, i.e. the detector may be used as a passage detector
in this mode.
The 4 minute and 40 minute settings work in the same way as the 1 second setting; however the
detector will now give outputs of 4 minutes or 40 minutes. If the vehicle which caused the inductance
change moves off the loop then the detector will go out of detect and this time will be reset to zero for
the next detect cycle. The detector may undetect before the expired time period if the change in
inductance for the vehicle is small.
The “no fixed time-out” setting does not have a fixed time period and the presence time is dependant
on the magnitude of the inductance change caused by the vehicle over the loop.
On times longer than 1 second there will be a “paralysis time” of approximately 2 seconds between
actuations.