Diablo DSP-19 User manual

Diablo Controls, Inc.
Copyright © 2017
Document: DSP19_MAN_A
Released: June 05, 2017
Pros Who Know Trust Diablo
User Manual
DSP-19
Loop and Mini-Loop Vehicle
Detector

DSP-19 User Manual Page 2 of 24 DSP19_MAN_A
1. Contents
Figures ....................................................................................................................................................................3
2. Introduction ...........................................................................................................................................4
Functional Data.......................................................................................................................................................5
Electrical Data.........................................................................................................................................................6
Environmental Data................................................................................................................................................6
Mechanical Data.....................................................................................................................................................7
3. Features and Functions...........................................................................................................................8
Solid-State Output ..................................................................................................................................................8
Detector Reset........................................................................................................................................................8
Presence Detection.................................................................................................................................................9
Pulse Detection.......................................................................................................................................................9
Sensitivity (Rotary Switch)......................................................................................................................................9
Frequency (DIP Switches 1 and 2) ........................................................................................................................10
Loop / Magnetometer (DIP Switch 3)...................................................................................................................10
Normal / Extended Presence (DIP Switch 4) ........................................................................................................10
Normal Sensitivity / Sensitivity Boost (DIP Switch 5) ...........................................................................................11
Fail-Safe / Fail-Secure (DIP Switch 6)....................................................................................................................11
Output Connector.................................................................................................................................................12
Indicators..............................................................................................................................................................12
4. Installation...........................................................................................................................................15
Detector Installation.............................................................................................................................................15
Loop Installation...................................................................................................................................................15
Mini-Loop Installation...........................................................................................................................................18
5. Configuration .......................................................................................................................................20
Wiring ...................................................................................................................................................................20
6. Troubleshooting ...................................................................................................................................21
No Power LED .......................................................................................................................................................21
Power LED Flashes Slowly (2Hz) ...........................................................................................................................21
Power LED Displaying 1 Flash On, Every Two Seconds.........................................................................................21
Power LED Displaying 2 Flashes On, Every Two Seconds .....................................................................................21
Power LED Displaying 3 Flashes On, Every Two Seconds .....................................................................................22
Power LED Flashes Off Every Two Seconds ..........................................................................................................23
Detect LED Intermittently Comes On / Stays On Without a Vehicle Present.......................................................23
Detect LED Will Not Come On With a Vehicle Present.........................................................................................24

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Figures
Figure 1: Product Views..............................................................................................................................................4
Figure 2: Physical Dimensions ....................................................................................................................................7
Figure 3: Outputs..................................................................................................................................................... 11
Figure 4: Power LED States...................................................................................................................................... 13
Figure 5: Detect LED States ..................................................................................................................................... 14
Figure 6: Loop Installation....................................................................................................................................... 17
Figure 7: Saw Cut for Home Run Exit and Chiseled Corner for Home Run Exit....................................................... 17
Figure 8: Typical Mini-Loop Installation .................................................................................................................. 18
Figure 9: Mini-Loop Side Installation....................................................................................................................... 19

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2. Introduction
The DSP-19 is a compact vehicle detector that will operate on any voltage from 8 to 35 volts DC. The low voltage
range is ideal for solar applications. The DSP-19 can be connected to a standard inductive loop or one of Diablo
Controls mini-loops. The Diablo Controls mini-loop is a small “pipe shaped” device approximately 4-1/2” by 1” and
is designed to be buried in the ground to detect vehicles. Contact Diablo Controls for more information on the
mini-loop. The DSP-19 can be used as either a safety loop or free exit loop detector. It also has the flexibility to be
either “fail-safe” or “fail-secure”. The DSP-19 has a single solid-state FET output.
The DSP-19 has 10 selectable sensitivity settings and uses a 6-position DIP switch to configure the detector. This
includes the Diablo Controls mini-loop selection as well as sensitivity boost, extended presence and fail- safe/fail
secure operation. This makes the DSP-19 very flexible and versatile for those installations that need a little more
than a standard detector
Figure 1: Product Views

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Functional Data
Sensitivity: Ten sensitivities are user selectable.
Setting
Sensitivity
Setting
Sensitivity
0
.48% ΔL/L
5
.08% ΔL/L
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
Frequency Settings: There are four frequency settings available. The actual loop frequency is
dependent on loop circuit inductance.
DIP Switch
Frequency
1
2
OFF
OFF
High
OFF
ON
Medium Low
ON
OFF
Medium High
ON
ON
Low
Inductive Loop Response Time: Response time is dependent on the sensitivity selected.
Setting
Response Time
Setting
Response Time
0
70ms ±10ms
5
70ms ±10ms
1
70ms ±10ms
6
140ms ±20ms
2
70ms ±10ms
7
140ms ±20ms
3
70ms ±10ms
8
140ms ±20ms
4
70ms ±10ms
9
140ms ±20ms
Mini-Loop Response Time: Response time is dependent on the sensitivity selected.
Setting
Response Time
Setting
Response Time
0
130ms ±10ms
5
130ms ±10ms
1
130ms ±10ms
6
250ms ±20ms
2
130ms ±10ms
7
250ms ±20ms
3
130ms ±10ms
8
250ms ±20ms
4
130ms ±10ms
9
250ms ±20ms
Vehicle Hold Time: In Normal Presence Mode: Approximately 1 hour for a detection of 1% ΔL/L.
In Extended Presence Mode: Approximately 1 to 2 days for a detection of 1% ΔL/L.

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Electrical Data
Loop Inductance: 20 microhenries to 1500 microhenries (including lead-in inductance). Not all
frequency settings are available at inductances below 30 microhenries.
Operating Voltages: One wide range power version:
8 volts to 35 volts DC
Solid State Output Rating: Maximum Output Current: 250 milliamps
Maximum Pull-Up Voltage: 30 volts
Maximum Voltage Drop Across Active Output: 0.3 volts
Current Draw: Without detection is 31 ma maximum
With detection is 40 ma maximum
Environmental Data
Operating Temperature: -35°F to 165°F (-37°C to 74°C)
Storage Temperature: -40°F to 176°F (-40°C to 80°C)
Humidity: Up to 95% relative humidity non-condensing

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Mechanical Data
Mounting Position: Any
Housing Material: Lexan
Housing Size: 2.362 inches (High) x 2.008 inches (Wide) x .866 inches (Deep)
60.00 mm (High) x 51.00 mm (Wide) x 22.00 mm (Deep)
Figure 2: Physical Dimensions

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3. Features and Functions
Solid-State Output
The DSP-19 has one solid-state (open-drain) output. Solid-state outputs have several advantages over relay
outputs:
•Allows for a smaller form factor
•Lower power consumption
•Outputs do not have to be debounced (relay contact bounce when closing)
•Higher reliability due to no moving parts
But they also have their limitations:
•Requires that the detector and the operator have the same DC common
•Requires a pull-up resistor to function correctly
•The output can only be pulled down to DC common (can only sink current)
•Limited current switching capability (250 milliamps)
•Polarity sensitive (will not work if connected backwards)
With proper engineering these limitations can be easily overcome and the benefits of the solid-state output can
be fully realized. Almost all operators are now designed to share their DC common with external devices and have
built in pull-up resistors on their inputs to facilitate working with solid-state (open-collector) outputs. These inputs
usually require less than 20 milliamps of current sinking capability to be activated.
The polarity issue is handled by the operator if the detector plugs directly in to the operator. If using an adapter
board like the RK-1 or RK-3, the negative side of the output is already connected to DC common. So the output is
simply connected to the desired termination point on the controller and it should all work.
The easiest way to envision the function of a solid-state (open-drain) output is to think of it as a normally open
relay contact with the relay common connected to DC common.
Detector Reset
When any of the DIP switches or the 10-position rotary switch is changed, 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. NOTE: If a vehicle is over the loop during the reset period it will not be
detected.
Both LEDs will turn off for 500 milliseconds at the start of the reset event. After that, the red LED will flash
according to its 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.
When a failure occurs, the output will be active if the detector is in the fail-safe mode. It will be inactive if in fail-
secure.

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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

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Frequency (DIP Switches 1 and 2)
When loops are installed sufficiently far apart, any two loops will not interfere with each other. However, if two
loops are fairly close together, say two to four feet apart, the inductive fields may couple together and may
interact causing intermittent false detections. The main variables for inductive coupling are loop size, distance
between loops, and the loop frequency. To aid in mitigating inductive coupling, each DSP-19 unit comes with two
frequency switches. They are binary coded allowing up to four different operating frequencies.
If there are suspicions that loops are interacting, change one of the detector’s frequency settings so that their
inherent frequencies are sufficiently different as to no longer interact. If the loops are the same size and number
of turns, setting one detector to high and the other detector to low will provide the maximum frequency
separation.
DIP Switch
Frequency
1
2
OFF
OFF
High
Factory Default
OFF
ON
Medium Low
ON
OFF
Medium High
ON
ON
Low
Loop / Magnetometer (DIP Switch 3)
The DSP-19 is capable of operating with either a standard inductive loop in the presence mode or the new mini-
loop (magnetometer) in the pulse on entry mode. In the magnetometer mode of operation the detector will only
hold a detection for 2 seconds. Therefore, if a vehicle stays over the sensor for more than 2 seconds it may
generate additional pulses for the same vehicle. The factory default is the inductive loop mode.
DIP
Switch 8
Loop Type
OFF
Inductive Loop
Factory Default
ON
Mini-Loop
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.
Normal / Extended Presence (DIP Switch 4)
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. For those instances where a
longer hold period is desired, extended presence is available.
The time it takes to complete the retuning process is dependent on the strength of the call being induced by the
vehicle. In the Normal Presence mode (DIP switch 4 off) this usually takes between 15 minutes and about 4 hours.
In the Extended Presence mode (DIP switch 4 on) the retuning process may take considerably longer, perhaps
over a day or so.

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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.
DIP
Switch 4
Presence Time
OFF
Normal Hold Time
Factory Default
ON
Extended Presence
The following figures show the effects of delay and extension on the A & B outputs when the detector is operating
in the loop mode. The numbers between edges are the number of seconds in that period.
Figure 3: Outputs
Normal Sensitivity / Sensitivity Boost (DIP Switch 5)
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 5
Sensitivity Boost
OFF
Disabled
Factory Default
ON
Enabled
Fail-Safe / Fail-Secure (DIP Switch 6)
On the DSP-19, the option for fail-safe or fail-secure only applies to the main output when in the inductive loop
mode. In general, a fail-safe detector will activate the output when the loop circuit is failed. This is useful on a
safety loop to prevent accidental closure of a gate on a vehicle. On the free exit loop this will keep the gate open
until the situation is fixed. Fail-safe is used in applications where it is important to allow traffic flow to continue.

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A fail-secure detector will not activate the output when the loop circuit is failed. This will keep the gate closed.
This is useful in high-security areas or installations where containment is needed.
The magnetometer mode is always fail-secure.
These failure modes only apply to the output when external power is applied. That is, the failure output is more
of a loop failure output than a total failure output. When placed in the fail-safe position, the main output will be
activated when the detector recognizes that the loop is somehow compromised, like if a loop wire is disconnected
from its terminal screw. If placed in the fail-secure position, the main output does not activate when a fault
condition is identified.
DIP
Switch 3
Failure Mode for Output A
OFF
Fail-Safe
Factory Default
ON
Fail-Secure
When a fault is identified the green Power LED will flash to indicate the type of fault that was found. See
Indicators –Power LED for more information on this display.
Output Connector
The DSP-19 connects as typical through its rear 9-pin connector. That is, loop inputs and power inputs. However,
the main output is through the 2-pin connector located on the top of the detector. The connector is a typical Euro
style screw terminal block. Looking straight on at the side label, the wires are inserted in the opposite side of the
connector and then torqued down with the appropriate screw. As the label denotes, the right-most screw is the
main output and the left-most screw the common.
Indicators
The DSP-19 is equipped with two (2) LED indicators: Power (Green) and Detect (Red).
Power LED –The green power LED indicates these possible states:
OFF The voltage applied to the detector is less than the minimum display voltage of
approximately 5 volts. The LED will be off.
LOW VOLTAGE The voltage applied to the detector is more than the minimum display voltage of
approximately 5 volts, but less than the minimum of 8 volts, the LED will be
blinking 250 ms on and 250 ms off.
RESET IN FAIL-SAFE At the start of a reset event (a DIP switch change, sensitivity change, or power
cycle) the LED will turn off for 500 milliseconds, on for 500 milliseconds, off for
500 milliseconds, and then display its normal state.
RESET IN FAIL-SECURE At the start of a reset event (a DIP switch change, sensitivity change, or power
cycle) the LED will turn off for 500 milliseconds, on for 500 milliseconds, blink

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repeatedly with 50 milliseconds on followed by 50 milliseconds off for one
second, and then display its normal state.
OPEN LOOP When the detector senses that the loop is open or the inductance is too high, the
LED will flash on once for 150 milliseconds every two seconds. This usually
indicates that there is no sensor attached or that the cable has been cut.
SHORTED LOOP When the detector senses that a loop is shorted or the inductance is too low, the
LED will flash on twice for 150 milliseconds every two seconds.
LARGE CHANGE FAULT When the detector senses that a loop is experiencing a large inductance change
(greater than 30%), the LED will flash on three times for 150 milliseconds every
two seconds.
PRIOR FAULT The detector is equipped with the ability to remember prior faults that have
occurred since the last power interruption or reset (changing a DIP switch or the
sensitivity). The detector will hold this status for one week and then
automatically clear the status. The display will be on with one, two, or three blinks
off depending upon the prior failure type. See chart below for actual timing.
NORMAL The LED is always on when the detector is in its normal state of operation.
Figure 4: Power LED States

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Detect LED –The red Detect LED is used to display the status of the main output. There are several different
statuses that can be displayed on this LED:
Off No vehicle present in the detection area or the detector has identified a fault and
has deactivated the main output because it is in fail-secure operation.
Reset in Fail-safe At the start of a reset event (a DIP switch change, sensitivity change, or power
cycle) the LED will turn off for 500 milliseconds, on for 500 milliseconds, off for
500 milliseconds, on for 500 milliseconds, and then finally display its normal state.
The main output will be activated during this time.
Reset in Fail-secure At the start of a reset event (a DIP switch change, sensitivity change, or power
cycle) the LED will turn off for 500 milliseconds, on for 500 milliseconds, blink
repeatedly with 50 milliseconds on followed by 50 milliseconds off for one
second, and then display its normal state. The main output will be deactivated
during this time.
Main Output Active A vehicle is detected and has activated the main output.
Figure 5: Detect LED States

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4. Installation
Detector Installation
Location: The detector should be installed in a weatherproof location that is near the loop. Ideally, a technician
should be able to see the loop and the detector at the same time.
Mounting: The detector will function when mounted in any orientation. If the operator does not have a connector
for the detector to directly plug in to, an adapter board will be needed (RK-1 or RK-3). Mount the adapter board
such that the switches and LEDs on the detector will be easily accessible for configuration and troubleshooting.
Wiring: If plugging the detector in to the operator, you should be certain that the operator pin-out for its
connector is the same as that of the DSP-19 detector and that the voltage supplied to the detector is between 10
and 30 volts DC.
If using an adapter board, terminate all wires on to the adapter board before plugging to detector into the board.
Wire nuts should never be used at any point in the loop circuit itself. All loop connections should be crimped or
screw terminals at a minimum and soldered for best long-term reliability.
Special attention should be paid to ensure that the loop wires remain tightly twisted together. An air gap between
the two wires for a loop may cause the detector to lock up if the wires are disturbed.
Remember that the DSP-19 uses solid-state outputs and can only sink current. Therefore, if you want to drive a
relay coil with an output, the other side of the relay coil must be connected to an appropriate voltage (for the coil)
positive DC supply. Using an AC relay is not possible and may damage the detector. The detector has snubber
diodes built in for all of the solid-state (open-collector) outputs in case they do drive a relay coil.
Loop Installation
The reliability and overall performance of the detector are greatly dependent on the loop itself. Several factors
go into a good loop installation: type of wire used, loop configuration, and installation practices.
Type of Wire Used: The wire used for wiring the loop should have a jacket of cross-linked polyethylene or similar
material that has very low moisture absorption properties. This would be a wire with an XLP jacket such as XHHW.
THHN or similar wire types should never be used for loop wire.
The gauge of the wire to use depends on two factors: Distance in cable feet from the loop to the detector and
stresses the wire may see. The gauge of the wire can be 20 AWG as long as the detector is within 50 feet of the
loop in cable distance. For 50 to 100 feet, use at least 18 AWG wire. At greater than 100 feet, use a 16 AWG wire
at a minimum. If the loop is installed in asphalt and there will be heavy vehicles or stopping and starting vehicles
in the loop area, a 14 AWG or 12 AWG should be used to provide additional strength to the loop. This helps
increase the life of the loop in areas where the asphalt may slowly move and/or deform due to wear.

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Loop Configuration: The size and shape of the loop will determine what type of vehicles it can reliably detect.
There are many variables that come into play including loop dimensions, percent of coverage, length of lead-in
wire, number of turns in the loop area, and detection height to name just a few of them. One common rule is
that the useable field height of a loop is 2/3 of the shortest leg of the loop. So if you plan on using a 2.5’ x 6’ loop,
the expected useable detection height would be 20” (The shortest leg is 2.5’ or 30”, 30” x 2 = 60”, 60” / 3 = 20”).
If the installation requires the detection of motorcycles as well as vehicles, the loop should go to within one foot
of the curb or roadway edge, whichever is present. If only motor vehicle detection is required, within three feet
of the curb or roadway edge is all that is required.
The number of turns to use in a loop is dependent on the size of the loop, the amount of metal (rebar, cables,
etc.), and distance from the loop to the detector. Rather than dive into all of the calculations to arrive at a value,
we will just use safe values. You can almost never have too many turns in a loop, only too few. For a loop size of
2’ x 6’, four turns will be sufficient unless there is metal in the loop area. In that case add at least one turn, and
two if possible. As the loop size reaches 6’ x 6’, four turns will work for most all installations. If you are unsure
about your particular installation, call tech support for guidance.
Installation Practices: Permanent loops should be installed into the road surface by cutting slots into the road
surface using a saw with an appropriate cutting disk for the road surface.
The slot cut should be wide enough that the wire being used will easily fit into the slot. This is needed so that the
loop sealant used can fully encapsulate the wire. When the wire fits tightly in the slot, the sealant may not be
able to get below the wire, leaving air pockets in the saw slot. If water finds its way in to these air pockets, over
time, freeze thaw cycles can slowly jack the loop out of the saw slot causing loop failure.
The saw slot should be deep enough that the loop wire will have a minimum of ½” of sealant over the top wire in
the slot. More is better. Going too deep with the saw cut is also a concern. Deep cuts in a road surface may
impact the structural strength of the roadway, especially if any reinforcement material is cut. Using a smaller
gauge of wire will allow for shallower saw cuts.
The corners of the loop should be crosscut at a 45°to help prevent damage to the wire insulation during
installation and temperature cycling. The angled cuts should be at least 9” back from where the corner would be.
The saw cuts should not go any further than necessary to insure that the saw slots are at full depth where they
meet.
Special consideration should be given to where the home run saw cut meets the loop saw cuts. Here either an
additional saw cut should be made as shown in Detail A or the inside of the sharp corner should be removed with
a chisel as shown in Detail B.
Once the saw slot has been cut, the slot should be cleaned of all loose material. High-pressure air should be
directed in to the saw slot to remove all debris. This will also help remove dust from the saw cutting operation
from the sides of the saw slot. This will allow better adhesion of the loop sealant to the saw slot.

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Figure 6: Loop Installation
Figure 7: Saw Cut for Home Run Exit and Chiseled Corner for Home Run Exit
BACKER ROD
PIECE
LOOP WIRE
SAW
CUTS
DETAIL A
DETAIL B

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The loop wire should be installed as a continuous piece of wire from the detector to the loop, all of the turns in
the loop, and back to the detector. Remember to make allowance for shrinkage in the wire length when the
portion of the wire not in the roadway surface is twisted. The twisting is important for dealing with electrical
noise. A splice of the loop wire should never be made in the roadway. If the loop wire needs to be spliced to
another cable to get to the detector, the splice should be done in a junction box and the connections should be
soldered and weatherproofed. Wire nuts should never be used at any point in the loop circuit.
In order to keep the loop wire at the bottom of the saw slot, 1” to 2” pieces of backer rod should be placed in the
saw slot every 1 to 2 feet. The backer rod should be sized such that it fits snugly in the saw slot. Use a blunt object
(not a screwdriver) to press the backer rod pieces down into the saw slot as far as they will go. Keeping the loop
wire at the bottom of the saw slot allows the loop sealant to provide the maximum amount of protection possible
from foreign object penetration. Never use a continuous piece of backer rod over the loop, as this would prevent
the loop sealant from encapsulating the loop wire.
The loop sealant used should be appropriate for the roadway surface that was cut. Generally, epoxy or polyester
based sealants are used for concrete surfaces and polyester or urethane based sealants are used for asphalt
surfaces. However, these are not hard guidelines and specific circumstances will determine which type of sealant
should be used.
Once the loop wire leaves the saw slot it should be twisted at least three times per foot. More is better. The
twists should be kept tight to be most effective in reducing the effects of electrical interference.
Mini-Loop Installation
Installation is straightforward. A 1½ to 2 inch diameter hole (6 to 12 inches deep) is drilled for the Mini-Loop. A
1 inch deep, ¼ inch wide saw cut from the hole to the edge of the road provides a path for the lead-in wire. The
Mini-Loop with lead-in is inserted into the hole and the hole is filled to 1 inch from the top with dry sand. Loop
sealant material is then used to fill the slot and top portion of the hole. 1 inch pieces of backer rod should be used
every foot of the saw slot to keep the lead-in cable at the bottom of the saw slot.
Figure 8: Typical Mini-Loop Installation

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It is important that the Mini-Loop be installed in a vertical position and that the vertical position of the Mini-Loop
be maintained. Under some soil conditions, installation can be further simplified by installing the Mini-Loop inside
a length of PVC pipe (not steel pipe) with an interior diameter of about 1½ inch. In this case, the hole must be
slightly larger than the outside diameter of the PVC pipe, typically 2 inches. After insertion of the PVC pipe and
Mini-Loop, all cavities are back-filled with fine, dry sand and the installation completed in the normal manner.
Side Detection Zone Placement
When the roadway is less than 11 feet wide, it may be possible to place the Mini-Loop on the side of the roadway
and achieve acceptable detection performance. The Mini-Loop can be installed at a 45 degree angle so that the
top of the sensor points towards where the vehicle is to be detected. This can be very useful when applications
where there is already an existing driving surface that the customer does no want distrubed.
Figure 9: Mini-Loop Side Installation
When the roadway is greater than 11 feet wide, requiring a greater detection zone, you have two options. First
is to add a second Mini Loop to the opposing side of the roadway. The probes must be wired in series. However,
this configuration cuts the sensitivity of the Mini-Loop in half and does not allow for different sensitivites for the
two Mini-Loops.
The second is to use another DSP-19 with it’s own Mini-Loop installed on the opposite side of the roadway. In this
configuration both Mini-Loops have full sensitivity and their sensitivities are individually adjustable.

DSP-19 User Manual Page 20 of 24 DSP19_MAN_A
5. Configuration
Wiring
There is only one wiring configuration (pin-out) offered for the DSP-19.
Pin
Function
1
Loop or Mini-Loop
2
Loop or Mini-Loop
3
No Pin
4
Not Connected
5
Not Connected
6
Not Connected
7
Not Connected
9
DC +
10
DC –and Output Common