DSP-19 User Manual
Page 9 of 24
DSP19_MAN_A
Presence Detection
Presence detection is only available in the inductive loop mode of operation (DIP switch 3 OFF). If the detector is
in the magnetometer mode of operation only pulse on entry operation is available.
While in the inductive loop mode of operation, the main output will always operate in the presence detection
mode. Once activated, the output will remain activated for as long as a vehicle is detected over the loop. After
four minutes of continuous detection, the detector will begin to slowly retune the detector with the goal of tuning
out the vehicle that stalled or parked on the loop over a relatively long time.
The time it takes to complete the retuning process is dependent on the strength of the detection being induced
by the vehicle. In the Normal Presence mode, it usually takes between 15 minutes and about 4 hours. In the
Extended Presence mode, the retune process may take over 24 hours. When the retuning process is complete,
any loop area that vehicles can still travel over will still detect the vehicle as expected. Once the vehicle leaves,
the detector will fully recover from the retuning process within 1 second.
Pulse Detection
In the magnetometer mode of operation, the main output is always configured for pulse on entry operation. The
pulse generated by the main output will be 250 milliseconds long. It is intended that there will be one output
pulse for each car driving over the loop. However, if a vehicle remains over the detection area for longer than two
seconds, a second pulse will be generated when the vehicle exits the area.
NOTE: The magnetometer mode of operation can not be used if the detector will function as a safety loop as
the mini-loop is not capable of presence detection.
Sensitivity (Rotary Switch)
The detector has ten (10) sensitivity levels. In most situations the sensitivity setting five (5) will work effectively.
For those situations where this setting is not sensitive enough, raise the sensitivity one level at a time until the
desired performance is obtained. For those situations where the detector is overly sensitive, lower the sensitivity
one level at a time until the desired performance is obtained. The factory default is five (5).
Like most inductive loop vehicle detectors, the DSP-19 directly measures the change in frequency of the loop and
from there, calculates the change in inductance when a vehicle interacts with it. The change in inductance is
measured as
%ΔL/L
(reads as “percent delta L over L”).
For the ten sensitivities, the thresholds are:
Setting
Sensitivity
Setting
Sensitivity
0
.48% ΔL/L
5
.08% ΔL/L
Factory Default
1
.32%
ΔL/L
6
.06% ΔL/L
2
.24% ΔL/L
7
.04% ΔL/L
3
.16% ΔL/L
8
.03% ΔL/L
4
.12% ΔL/L
9
.02% ΔL/L
