Decatur Electronics SI-3 User manual

User’s Manual
Rev: 5-14-19
SI-3™
System Interface 3

Table of Contents
Welcome .............................................................6
About This Manual ....................................................7
1 Safety Information ....................................................7
2 Receiving Inspection ..................................................8
3 Getting Started .......................................................9
3.1 Introduction ......................................................9
3.2 Connecting The Serial Cable.......................................9
3.3 Optional Programming Cable ....................................10
3.4 Mounting Conguration .........................................10
4 Conguring the SI-3™ ................................................11
4.1 Equipment Needed ..............................................11
4.2 Device Conguration ............................................11
4.3 Conguration Notes .............................................14
4.4 Baud Rate .......................................................14
4.5 Measurement....................................................14
4.6 Min/Max Speed ..................................................14
4.7 Target Report ....................................................14
4.8 Target Select.....................................................15
4.9 Cosine Horizontal and Cosine Vertical.............................15
4.10 Update Rate ....................................................15
4.11 Hold Time and Speed Lock ......................................15
4.12 Sensitivity ......................................................15
4.13 Serial Protocol ..................................................16
4.14 Start and Stop Output Buttons ..................................17
4.15 Radar On/O Button ............................................17
5 Performance Tips ....................................................18
5.1 How Radar Works ................................................18
5.2 Interference Sources .............................................18
5.2.1 Angular Interference (Cosine Eect) ............................18
5.2.2 Fan Interference ...............................................20
5.2.3 Electromagnetic Interference (EMI) .............................20
5.2.4 Feedback Interference .........................................20
5.2.5 Multi-Path Beam Cancellation ..................................20
5.2.6 Radio Frequency Interference (RFI) .............................20

5.2.7 Scanning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2.8 Environmental Factors: Wind, Rain, Snow .......................21
6 Testing The Device ...................................................22
6.1 Tuning Fork Test .................................................22
7 Care, Cleaning, and Storage ..........................................23
8 Specications ........................................................23
8.1 Antenna Parameters .............................................23
8.2 Environment ....................................................23
8.3 Speed Range Parameters ........................................23
8.4 Power Consumption ............................................23
9 Legal Requirements ..................................................24
9.1 Documents .....................................................24
9.2 FCC Statement..................................................25
9.3 Conditions......................................................25
9.4 Installer Note ....................................................25
9.5 End User Note ...................................................25
10 Frequently Asked Questions (FAQ) ....................................25
11 Warranty.............................................................26
12 Service Return Procedure.............................................27
13 How To Order Additional Products ....................................28
Appendix A - SI-3 Serial Commands .......................................29

SI-3™User’s Manual
4
Welcome To Decatur Electronics, Inc.!
Thank you for choosing this Decatur Electronics product—the
System Interface 3 (SI-3)™, a highly advanced directional radar unit
that will reward your department with years of dependable service.
The SI-3™ incorporates high performance and long range, with many
leading features. We urge you to study this manual before using the
SI-3™ so you can maximize the benets of this sophisticated radar
device. We believe you will be pleasantly surprised by the features
and advantages.
If you are as pleased with its performance as we think you will be,
ask your Decatur sales representative about other Decatur products
including the Genesis™ line of radars, the Onsite™ line of speed
trailers, dollies, pole signs and the Responder™ line of in-car video
systems.
Try any one of our products and see if you don't agree that it is the
best-in-class!
—The Management and Sta at Decatur Electronics

SI-3™User’s Manual
5
About This Manual
This manual contains valuable information to help you set up, use
and maintain your radar, so you can optimize its life and keep it at
peak performance. Please take a moment to read through it, and
keep it handy for future reference.
Note the following symbols in this manual:
Indicates a warning message about safety
precautions. Please read it carefully.
Indicates a helpful tip or precaution to note.
1. Safety Information
All service needs should be referred back to the manufacturer.
WARNINGS
• Do not over voltage the radar - it can damage the unit!
• The SI-3™ is designed to operate o of conventional
+12 VDC (+10.8 to +16.5 VDC) from the serial cable.
Important Warnings
• Opening the SI-3™ automatically voids any warranty
still in eect. There are no user serviceable parts inside.
• Do not expose the SI-3™ to excessive moisture. Never
submerge the device.
• Do not drop the SI-3™ on hard surfaces since damage
could occur. Units damaged by dropping or abuse are
not covered for warranty repair.
Violation of these guidelines may void the warranty.

SI-3™User’s Manual
6
2. Receiving Inspection
• When you receive your SI-3™, inspect it for any freight damage
that might have happened during shipping or unloading. Take
pictures to document any damage.
• Notify the freight company immediately of any damage,
preferably while the driver is present. Record the damage on the
bill of lading and keep a record of the problems or damage.
• The package should include the following pictured items along
with this User’s Manual.
SI-3™ S785-1-0
Programming USB Drive
S900-34
Tuning Fork
S769-127-0
Optional - Programming cable

SI-3™User’s Manual
7
3. Getting Started
3.1 Introduction
The SI-3™ is a radar specically designed to measure speeds and
export that speed information as RS232 data via the attached
serial cable. This allows the SI-3™ to be used for a wide range
of applications such as Radar Speed Trailers, trac speed data
collection (when used with the Decatur EZ Stat™ data logger) or
other uses where speed monitoring is desired. The SI-3™ comes
with a Programming disk that allows the user to congure certain
parameters of the SI-3™ for specic applications. Refer to Chapter 4
for conguration information. Additionally, a Radar Monitor program
is also available that allows you to display speed information on your
computer and record that information to a text le for analysis.
3.2 Connecting the Serial Cable
The SI-3™ operates o of +12VDC and is equipped with a specialized
DB-9 serial connector that contains provisions for powering the unit.
When connecting the cable it is important to understand that unlike
standard RS232 serial connectors that have no +12VDC provisions
the SI-3's™ serial connector has two pins dedicated to B+ and ground
for the purpose of powering the unit. Figure 3.2 shows the pin
arrangement.
Figure 3.2
Front view SI-3™Serial Connector
Pin 1 = +12VDC (power) (red wire)
Pin 2 = RS232 TX (white wire)
Pin 3 = RS232 RX (green wire)
Pin 4, 6 ,7 = N/C
Pin 5 = RS232 Ground (brown wire))
Pin 8 = Remote ON (blue wire)
Pin 9 = Ground (power) (black wire)

SI-3™User’s Manual
8
3.3 Optional Programming Cable
For conguring and testing purposes a programming cable is
available. The cable is designed with two DB-9 connectors and a
black and red wire for supplying B+ and ground to the SI-3™. One
end of the cable plugs into the serial port of a computer and the
other end into the SI-3™. The same end that plugs into the SI-3™ has a
red wire that is connected to +12 VDC and a black wire that connects
to ground. A regulated power supply can be used to supply the +12
VDC. Once the programming software is installed on the computer
then the SI-3™ can be accessed and parameters changed to meet
your application. Refer to Chapter 4 for programming information.
Figure 3.3
Optional Programming Cable
3.4 Mounting Conguration
The SI-3™ utilizes a single mounting point designed for quick, easy
installation. A standard ¼ x 20 bolt is used to mount the SI-3™ .
Figure 3.4
S785-30-0
(3 foot cable)

SI-3™User’s Manual
9
4. Conguring the SI-3™
4.1 Equipment Needed
• SI-3™ radar device
• SI-3™ Programming cable (S769-127-0)
• PC with either a usable RS232 serial port or a USB-to-RS232
adapter.
• RS232 cable to connect between the Power and
Communications adapter and the PC (if needed). This cable is a
9-pin RS232 cable with a male connector on one end and female
connector on the other.
• SI-3™ conguration USB Flash Drive (S785-1-0)
• 12V power supply
4.2 Device Conguration
1. Apply 12VDC power to the SI-3™ through the programming
cable. Open and run the SI-3™ Cong (conguration) program;
the opening screen is shown in Figure 4.2a.
Figure 4.2a
Opening Screen

SI-3™User’s Manual
10
2. The SI-3™ is designed to be connected to the computer's serial
port. However if you do not have a serial port and are using a
USB to Serial adapter make sure the adapter has been installed
per the instructions that came with it. Next, connect the SI-3™
to the computer through the adapter and check the Device
Manager, Ports. The port assignment will appear as "USB Serial
Port". Note the port assignment. The example in Figure 4.2b
shows that Port 4 has been assigned. Your port assignment may
be dierent and the port assignment can change the next time
the USB to Serial adapter is plugged in.
Figure 4.2b
Device Manager screen
2. From the Conguration Program screen select the COM port
that your PC has assigned. If you are connecting through the
computer's serial port, it will normally be "Com 1" or "Com 2". If
you are using the USB to Serial adapter, use the port shown in
Device Manager/Ports.
3. Change the baud rate if necessary – the SI-3™ default baud
rate is 9600. Press the "Connect" button near the top of the
window. SI-3™ Cong will query the RS232 line to see if an SI-3™
is connected to the computer. If it responds with the“Unable to

SI-3™User’s Manual
11
connect”message in the status bar on the bottom of the window
you need to check your connections between the PC and the SI-
3™.
4. If SI-3™ Cong is able to connect to the SI-3™, the screen
will appear as shown below in Figure 4.2c. In this screen the
information that appears accurately depicts the present
conguration of the SI-3™. Any changes made to the SI-3™
conguration are sent and stored in non-volatile memory. If
you turn o the SI-3™ unit while the SI-3™ Cong program is
connected, just press the "Disconnect" button and reconnect.
Figure 4.2c
Connected
Any grayed-out box such as the serial number box is for reference
only and cannot be changed. The "OK" button sends an OK
command to the device which then responds with the message “OK”.
This feature can be used to check communication status at any time.

SI-3™User’s Manual
12
The "Defaults" button sends a command to put the conguration
back to the factory default settings. If you have changed the baud
rate and have then pressed the Default button and suddenly nd
that the SI-3™ will no longer respond to commands; you need to
reconnect at 9600 baud before you can change the SI-3™ back
to your desired baud rate. The "Get Info" button retrieves the
present conguration from the SI-3™ and updates the displayed
conguration. This command can be used to resync the SI-3™ Cong
program with the SI-3™ if you’ve power-cycled the SI-3™ while it was
connected to the SI-3™ Cong program.
4.3 Conguration Notes
With the exception of baud rate, all changes occur immediately and
do not require a reboot of the SI-3™ to become operational. When
baud rate is changed it takes eect the next time the SI-3™ is power-
cycled.
• Please wait 2 seconds after the last conguration
command before disconnecting the power to allow the
SI-3™ to record the setting in ash memory.
4.4 Baud Rate
The "Baud Rate" can be 1200, 2400, 4800, 9600, 19200, 38400, 57600,
or 115200 bits per second. The SI-3™ always uses 8 bits, no parity, and
one stop bit for its serial port conguration.
4.5 Measurement
MPH = miles per hour, KPH = kilometers per hour, MPS = meters per
second, and FPS = feet per second.
4.6 Min/Max Speed
No vehicles will be reported outside the minimum and maximum
congured speeds.
4.7 Target Report
The Target Report has three selections. Choosing the "All" selection
will display vehicle speeds coming towards or away from the SI-3™.

SI-3™User’s Manual
13
"Approach“ will show vehicle speeds coming towards SI-3™, and
"Recede" will show vehicle speeds going away from the SI-3™.
4.8 Target Select
A Target Select value of “Strong” is the standard SI-3™ conguration.
Changing to “Fast” will report the fastest vehicle seen within the
range of the SI-3™.
4.9 Cosine Horizontal and Cosine Vertical
For bridge-type installations where the SI-3™ is over the trac and
pointing slightly down, the vertical angle can be entered here to
ensure that the SI-3™ calculates the correct vehicle speeds. For
installations where the SI-3™ is at a signicant angle from the road,
the horizontal angle can also be congured. These two may be used
together. Keep the angles between 0 and 45 degrees for maximum
accuracy.
4.10 Update Rate
The selected message format will be sent in whatever time interval
(in milliseconds) that you set. The "Update Rate" can be as low as 20
milliseconds. The number should be a multiple of 20 milliseconds.
The "Update Rate" and the amount of serial port activity do not aect
the measurement accuracy of the SI-3™.
4.11 Hold Time and Speed Lock
When the "Speed Lock" is congured as "Use Hold Time", the "Hold
Time" value indicates the time the vehicle speed is displayed after
the vehicle moves out of range. If the "Continuous Update" is selected
this value has no aect.
4.12 Sensitivity
The SI-3™ is shipped with a default "Sensitivity" of 9, this should work
for most applications. The sensitivity can be increased for longer
range or decreased for closer range. If the sensitivity is too low the
SI-3™ may take too long to lock onto and display a speed.

SI-3™User’s Manual
14
Typical ranges for an on-coming mid-sized sedan are:
Setting Range (feet)
1 350
2 575
3 800
4 950
5 1300
6 1700
7 1875
8 2400
9 2800
10 >3000
The distances will vary based on location, body of the car and
alignment of the antenna. It is normal for the range to vary by 10%
on identical cars.
4.13 Serial Protocol
Refer to the product manual for more information on which protocol
to use. <D> is a direction character that is “+” for vehicles coming
towards the sign, “-“ for vehicles moving away, and “?” when the
direction cannot be determined. [S] represents the displayed speed.
If a period is within the square brackets it is the decimal point. Any
zeros are sent as described and do not change with a vehicle’s speed.
The <cr> signies the end of the outgoing message. The default
setting is <D>[SSS.]<cr>. Other protocols listed are used by Decatur
for testing purposes. Zero Suppress
When this value is selected the SI-3™ will not send any information
over the RS232 port unless a vehicle is detected.

SI-3™User’s Manual
15
• When a serial protocol is running and a command is
sent to the SI-3™, the SI-3™ does receive and perform
the requested function. However, the returned "OK"
may be inserted anywhere in the data stream and
the resulting action on the host computer can not
be guaranteed. Example: The protocol is sending out
"123.4" If a command is sent to the SI-3™, the response
may be 12OK3.4". For this reason it is recommended
that the "Stop" command be sent prior to any change
in serial protocol if a serial protocol has been selected
previously.
4.14 Start and Stop Output Buttons
These buttons are used to start and stop the continuously updated
serial protocol. Any congured Serial Protocol will resume periodic
data transmission after a power-cycle. The Stop command is used to
temporarily stop the periodic data transmission. This Stop state is not
retained after a power-cycle. The Clear Window button will clear the
output window.
4.15 Radar On/O button
The Radar On / O buttons turn the radar transmitter on and o.

SI-3™User’s Manual
16
5. Performance Tips
Understanding potential radar interference and what to do when it
occurs can greatly increase the radar’s performance.
5.1 How Radar Works
Determining an object’s speed begins with the radar transmitting
a beam of microwave energy (radio waves) at an approaching or
departing target. When energy from this beam strikes a target, a
small amount of the beam is reected back to the antenna. The
reected signal frequency shifts by an amount proportional to the
speed of the target. This is known as the Doppler eect. The radar
device then determines the target speed from the dierence in
frequency between the reected and transmitted signal.
5.2 Interference Sources
When properly installed and operated, Doppler radar technology
is extremely accurate and reliable. However, variations in the
environment can cause situations and circumstances which can
cause spurious (erratic and unusually low or high) speeds to
display. Signs that a speed is spurious can include the following
characteristics:
• A reading appears when no target is in the operational range of
the antenna.
• A target entering the operational range overrides the
interference signal, causing the display speed to change
suddenly to the target’s speed.
• Speeds are irregular.
5.2.1 Angular Interference (Cosine Eect)
The cosine eect causes the system to display a speed which is
lower than the actual target speed. This condition occurs when
the target’s path is not parallel to the antenna such as the target
vehicle traveling on a curve or hill.

SI-3™User’s Manual
17
As the angle between the beam of the antenna and the target
increases, the displayed speed decreases. Ideally, an angle of zero
(0) degrees is preferable, because the displayed speed is the actual
target speed. However, in all uses of police radar, the radar device is
always at a slight angle to the target vehicle to avoid collisions.
Velocity
Vector
Angle
Radar
Figure 5.2.1
An angle between the antenna and the
target causes the cosine eect
The following table shows the eect that an increasing angle has
on a displayed speed.
Horizontal Angle Degrees
Actual
Speed
0° 1° 3° 5° 10° 15° 20° 30° 45° 60° 90°
Displayed speed:
30 mph 30 29 29 29 29 28 28 26 21 15 0
40 mph 40 39 39 39 39 38 37 34 28 20 0
50 mph 50 49 49 49 49 48 46 43 35 25 0
60 mph 60 59 59 59 59 57 56 51 31 30 0
70 mph 70 69 69 69 68 67 65 60 49 35 0
80 mph 80 79 79 79 78 77 75 69 57 40 0
Table 5.2.1
Actual and displayed speeds at antenna-to-target angles

SI-3™User’s Manual
18
Small angles (less than 10°) have little eect on accuracy. As the
angle increases, the displayed speed decreases. At 90°, the target
speed is 0—grossly incorrect.
5.2.2 Fan Interference
Fan interference is one of the most common forms of interference
that you are likely to experience. It is caused when the radar
measures the speed of a blower fan that is with in the beam path of
the radar. If the SI-3™ is used inside of a building keep in mind that
furnace and air conditioner fans can cause interference. To correct
this, relocate the radar so it does not display spurious speeds or
turn o the fan motor.
5.2.3 Electromagnetic Interference (EMI)
Operating electric motors can produce EMI. EMI from power seats
or windshield wipers can also produce spurious target speeds. To
correct the interference, simply turn o its source.
5.2.4 Feedback Interference
When the radar beam is directed at computer screens, streetlights,
and other electronic devices, it can display spurious speeds. To
correct the interference, relocate the SI-3™.
5.2.5 Multi-Path Beam Cancellation
If multi-path beam cancellation occurs, the target vehicle speed
sporadically blinks and reappears at semi-random intervals. This
type of interference occurs when the radar loses track of a target
because the target is reecting two or more signals, which are
interfering with each other. The SI-3™ is immune from multi-path
cancellation.
5.2.6 Radio Frequency Interference (RFI)
The system can inadvertently process radio energy as Doppler
speeds, including that from 2-way radios, airport radar, microwave
transmission towers, CB radio transmitters, and AM/FM
transmission towers. For this type of interference to occur, the SI-3™
must be operating very close to the radio transmitter.

SI-3™User’s Manual
19
5.2.7 Scanning
The SI-3™ is designed to be used while attached to a solid mount
position. Moving or “scanning” the antenna past stationary objects
can cause the system to detect motion. Obtaining a speed reading
from scanning will not happen when you properly use the radar
and is considered deliberate misuse of the system.
5.2.8 Environmental Factors: Rain & Snow
Environmental factors such as rain or snow can reduce the range
(distance) at which a target can be detected. However, these
factors will not aect accuracy.

SI-3™User’s Manual
20
6. Testing the Device
6.1 Tuning Fork Test
You can verify signal processing accuracy by using a tuning fork,
which comes with the radar. There is a one minute time window
from when the SI-3™ is rst powered on in which you can test the
unit using a tuning fork. After one minute the SI-3™ switches to
directional mode and the fork will no longer be read.
To begin the test, tap the tines of the fork on a rm, non-metallic
surface. The tuning fork will ring audibly. Then place the tuning fork
that you tapped with the narrow side facing about 3 inches directly
in front of the antenna. Compare the speed in the display window to
the speed stamped on the fork. If the dierence is within ±1 display
unit, the SI-3™ is working properly.
Figure 6.1
Place the vibrating tuning fork about 3 inches in front of the antenna
If the device does not display the expected speed, contact Decatur
Electronics Customer Service at 800.428.4315 to arrange for service.
• Only tap the tuning fork against hard plastic, wood,
and materials that are softer than metal. Repeatedly
tapping the tines on hard surfaces, such as metal and
concrete, can damage the tines and invalidate the fork
for future tests.