
DSP-22-2 User Manual
Page 10 of 25
DSP-22-2_MAN_E
raise the sensitivity. For those situations where the detector is overly sensitive, lower the sensitivity one level at
a time until the desired performance is obtained. Remember that semi-trucks look much smaller than a car. So,
do not set or test the sensitivity using a passenger vehicle if semi-truck traffic will be seen over the loop. The
factory default is low (DIP switch 1 OFF and DIP switch 2 OFF).
Like most inductive loop vehicle detectors, the DSP-22-2 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 four sensitivities, the detection thresholds are:
DIP Switch
Channel 2 Sensitivity
4
5
OFF
OFF
.32% ΔL/L Low
OFF
ON
.16% ΔL/L Medium Low
ON
OFF
.08% ΔL/L Medium High
ON
ON
.04% ΔL/L High
Channel 2
–
Normal Sensitivity / Sensitivity Boost (DIP Switch 6)
Each channel of the detector has a user selectable feature that increases the sensitivity of the detector after initial
detection. This feature is most often used to allow a detector to have a lower starting sensitivity and then increase
it after a vehicle has been detected. This is useful in situations where high-bed tractor-trailer vehicles will be
passing over the loop. With this feature the detector may be able to detect the high-bed portion of the vehicle
without having to be overly sensitive and susceptible to false detections. NOTE: If detection of high-bed tractor-
trailers is required, correctly sized loops must be used.
DIP
Switch 6
Function
OFF
Channel 2 Normal Sensitivity
ON
Channel 2 Sensitivity Boost
Channel 2
–
Presence / Pulse (DIP Switch 7)
The operating mode for channel 2 is selected with DIP switch 7 (Presence or Pulse) and affected by the setting of
DIP switch 8 (Loop or Probe). Presence detection for channel 2 is only available in the inductive loop mode of
operation (DIP switch 8 OFF). If channel 2 is in the probe mode of operation only pulse on entry operation is
available regardless of the setting of DIP switch 7.
In the Presence mode of operation, 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 a proprietary
algorithm that is designed to be able to reliably detect the vehicle for long periods of time (days or even weeks)
while still being able to drop the detection once the vehicle exits the loop.
When the probe mode of operation is selected (DIP switch 8 ON), pulse on entry is the only detection mode of
operation for Channel 2. If DIP switch 8 is OFF and DIP switch 7 is ON, Channel 2 is in the pulse mode.