DSP-22-1 User Manual
Page 7 of 22
DSP-22-1_MAN_D
2.
Features and Functions
Detector Reset
When any of the DIP switches are changed, the reset button is pressed, or power is cycled to the detector, the
detector will perform a reset. The reset event will last for two seconds while the detector initiates any changes
and waits for all systems to stabilize.
Both LEDs will turn off for 500 milliseconds at the start of the reset event. After that, the Detect 1 LED will flash
according to the fail-safe or fail-secure mode of operation. A flash rate that is the same as the power LED indicates
the output is operating as fail-safe. A much faster flash rate indicates that the output is operating in the fail-secure
mode.
NOTE:
If a vehicle is over a loop during the reset period it will not be detected.
Channel 1
–
Sensitivity (DIP Switches 1 and 2)
Channel 1 has four possible sensitivity levels. In most situations the sensitivity setting medium high (DIP switch 1
OFF and DIP switch 2 ON) will work effectively. For those situations where this setting is not sensitive enough,
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-22-1 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 1 Sensitivity
1
2
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 1
–
Normal Sensitivity / Sensitivity Boost (DIP Switch 3)
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
