Nortech DU 100 User Manual

Nortech International (Pty) Ltd
P O Box 4099 32A Wiganthorpe Road
Willowton Hub Pietermaritzburg
Pietermaritzburg 3201 South Africa
3200 South Africa Reg. No. 98/10951

Tel: [phone] Int. Tel: [phone]
Fax: [phone] Int. Fax: [phone]
Email: [e-mail] URL: www.nortech .co.za

NORTECH
All rights reserved
Copyright
Document No. : 895UM0001-02

Date of issue : May 2001

©

2000

DU 100

USER MANUAL

Table of Contents

1. INTRODUCTION............................................................................................ 3

2. TECHNICAL SPECIFICATIONS……………………………………….

3. OPERATIONAL INSTRUCTIONS.....................................................……

3.1 Intelligent Power Control...........................................................................….. 4

3.2 Display Contrast/Viewing Angle…………………………………………….

3.3 Data Acquisition……………………………………………………………..

3.4 DiagnosticOperation...................................................................................…. 5

4. OPERATIONAL MODES............................................................................. 6

4.1 Loop (Loop).................................................................................................... 6

4.2 Frequency (Freq)............................................................................................. 7

4.3 Sensitivity (Sens)............................................................................................. 8

4.4 Status (Stat)..................................................................................................... 9

4.5 Time (Time).................................................................................................... 10

4.6 Crosstalk (Xtlk)............................................................................................... 11

4.7 Built In Self Test (Test)................................................................................. 13

5. THEORY OF APPLICATIONS................................................................... 14

5.1 Loop Frequency and Inductance Change........................................................ 14

5.2 Loop Frequency Drift....................................................................................... 15

5.3 Detection Sensitivity........................................................................................ 16

5.4 Detector Status................................................................................................ 16

5.5 Historical Fault Data........................................................................................ 17

5.6 Crosstalk Prevention....................................................................................... 18

6. APPENDIX A – TYPICAL VALUES……………………………………… 19

4

4
5

895UM0001_02 DU100 User Manual Page 2 of 19

. INTRODUCTION

providing installation/service personnel with positive verification of the correct
operation of a vehicle detector installation. It may only be utilised in conjunction with
diagnostic compatible vehicle detector products from Nortech Industries.

Current operational and historical data are transferred form the vehicle detector to the
DU100 by means of an optical link. Data transmission form the vehicle detector unit
occurs continuously so no service disruption is necessary. Received data is verified
for integrity by means of a cyclic redundancy check (CRC), processes, and then
displayed on a LCD screen.

The Nortech DU100 Diagnostic Unit is a hand held test instrument capable of

1.1 The DU100 can be used with the following inductive loop detectors;
PD130, PD139 (excluding I²C models), PD140, PD230, PD239 (excluding I²C models),
PD240, TD136, TD136 Enhanced, TD250, TD250L, TD250LS, TD252.

1.2 Related Documents

“Inductive Loop Vehicle Detection” Document No. MKT01.

1.3 This manual covers the following units;

895FT0001 – DU100 Diagnostic unit – English
895FT0002 – DU100 Diagnostic unit – German
895FT0003 – DU100 Diagnostic unit – French
895FT0004 – DU100 Diagnostic unit – Italian
895FT0005 – DU100 Diagnostic unit - Spanish

895UM0001_02 DU100 User Manual Page 3 of 19

2. DU100 TECHNICAL SPECIFICATIONS

Frequency Resolution 1Hz

Sensitivity Resolution 0.001 % ∆ L/L

Display Element 2 line x 16 Character LCD

Display Contrast Adjustable via multi-function keyswitch

Keyswitch 1 x Mode Selection, 1 x Power-on/execute

Auto Power off 2 Minutes after last operation

Optical Receiver Detachable wand with photo-diode

Power Supply 4 X 1.5V AA dry cell

Battery Life > 10 hours continuous

Operating Temperature Range 0°C to + 50 ° C

Dimensions 200mm (h) x 100mm (w) x 40mm (d)

Weight 380gms including batteries

3. OPERATIONAL INSTRUCTIONS

3.1 Intelligent Power Control

The DU100 Diagnostic Unit may be powered-up by pressing either the SELECT or
ENTER key. The unit may be turned off by the simultaneous pressing of both keys.
Automatic power-down will occur after the unit has been left unused after two
minutes.

3.2 Display Contrast/Viewing Angle

The display contrast may be adjusted by holding down either key: SELECT for
lighter, ENTER for darker.

895UM0001_02 DU100 User Manual Page 4 of 19

3.3 Data Acquisition

optical link. An optical wand ( normally located in the zippered side pocket of the
DU100 bag) should be plugged into the jack socket at the top of the unit and the unit
should be powered-up. When the optical wand is brought into close proximity of the
red “RUN LED” of the detector under test, the DU100 will emit audible beeps as it
acquires data. A single beep received indicates that sufficient data has been received
and the optical link may be broken at this stage to enable operator interrogation.
Alternatively, the optical link may be maintained in order to facilitate continuous data
transfer and updating.

Data is extracted form the vehicle detector under test by means of a unidirectional

3.4 Diagnostic Operation

After pressing any button and powering the diagnostic unit, information can be
acquired ( indicated by an audible beep ). The DU100 will display the type of the
vehicle detector under test ( e.g. PD130 ) and its software release version on the top
line of the two display screen. The lower line will consist of a cyclical menu. Each
time the SELECT key [¤] is pressed, the cursor will jump to the next menu option.
Menu options, once selected, are activated by means of the ENTER key[ ↵ ].

895UM0001_02 DU100 User Manual Page 5 of 19

4. OPERATIONAL MODES

Each operational mode corresponds to a menu option. These are discussed below.

4.1 Loop (Loop)

e.g.

Frequency

The loop frequency and change in inductance are displayed for the currently selected
channel. The currently selected channel is displayed in the top right hand corner. This
mode can be used to monitor the change in loop frequency and inductance as a vehicle
traverses the loop.

SELECT [¤] advance to the next detector channel ( multi-channel units only ).

ENTER [ ↵ ] returns control to main menu.

The inductance change (%∆L/L) is a measure of the magnitude of detection. Typical
passenger vehicles register a peak change of the order of 1% - 3% ∆ L/L. Poorly
designed loop installations can lead to this value being significantly reduced.

Below are typical inductance changes (%∆L/L) for a loop measuring 2m x 1m and
having 3 turns; with no wire mesh re-inforcing.

KHZ % ∆ L/L 1

20.231 1.371

Channel

VEHICLE TYPE

BICYCLE 0.04 %

MOTORBIKE 0.12 %

ARTICULATED TRUCK 0.38 %

FOUR WHEEL DRIVE 0.40 %

5 TON TIP TRUCK 0.45 %

MOTOR CAR > 1.00 %

FORKLIFT > 1.00 %

The inductance change parameter can also be utilised to determine whether the
inductance change registered by a particular vehicle ( e.g. high undercarriage of a
commercial vehicle ) is of sufficient magnitude to break through the sensitivity
threshold of the vehicle detector. The relevant sensitivity threshold value may be
obtained from the detector data sheet and is typically 0.02% ∆ L/L.

895UM0001_02 DU100 User Manual Page 6 of 19

∆ L/L

4.2 Frequency ( Freq )

The loop frequency and frequency drift ( since last reset/retune ) are displayed for
the currently selected channel. The currently selected channel is displayed in the top
right hand corner. The drift measurement gives an indication of the quality of a loop
installation.

Note: The drift value is an historical value and is cleared each time the detector
resets/retunes.

SELECT [¤] advances to the next channel ( multi-channel units only ).

ENTER [ ↵ ] returns control to the main menu.

The loop frequency value represents the frequency of the AC signal energising the
inductive loop and should be in the range of 20 KHz - 150 KHz. It is determined both
by switch settings on the detector and loop geometry ( size and no. of turns ). Loops
in close proximity to one another require a frequency spacing of greater than 2KHz
typical to avoid crosstalk ( not necessary for multiplexed multi-channel detectors ).

The frequency drift is used to determine the quality of the loop and feeder cable
typically the frequency drift should be less than 3 %. Typically frequency drift of
greater than 0.1 % per minute (typical) will cause a detect.

Factors affecting frequency drift are:

• Mechanical movement of loop wires.

• Deterioration of loop wire insulation allowing penetration of moisture.

• Temperature variation of the loop environment.

[Refer to Section 5.2]

e.g.

KHz Drift 1

20.231 0.20%

895UM0001_02 DU100 User Manual Page 7 of 19

4.3 Sensitivity ( Sens )

The minimum and maximum change in the loop inductance during vehicle detection
are displayed for the currently selected channel. The currently selected channel is
displayed in the top right hand corner. These values represent absolute minima and
maxima and are valid since the last detector reset/retune.

Note: MIN and MAX are historical values which are cleared each time the detector
resets/retunes. Their value will remain at zero until the first detect.

SELECT [ ¤ ] advances to the next channel ( multi-channel units only ).

ENTER [ ↵ ] returns control to the main menu.

The maximum value (MAX) corresponds to the greatest magnitude of detection for all
vehicles since the last reset of the vehicle detector. If the vehicle detector is manually
reset before the loop is traversed by a vehicle, the MAX display will indicate the
highest detection level over the profile vehicle. Typical levels for a passenger vehicle
are 1% - 3% ∆ L/L. As the sensitivity of the installation can be severely degraded by
poor layout or proximity of ferrous metal, this value is useful for site-to-site
comparisons ( i.e. using the same vehicle ).

The minimum value (MIN) indicates the smallest magnitude of inductance change
( resulting in a detect ) for all vehicles, since the last reset of the vehicle detector. Over
a relatively short span of time, this value will tend towards the sensitivity setting of
the vehicle detector.

A detection change of greater than 15 % (typical), will cause the detector to re-tune.
( A change greater than 15 % is considered a fault condition ).

e.g.

MIN MAX 1

0.110% 3.401%

895UM0001_02 DU100 User Manual Page 8 of 19

4.4 Status ( Stat )

The loop status of the currently selected channel is displayed. The currently selected
channel is displayed in the top right hand corner.

Possible loop status conditions include:

i. Undetect

ii. Detect

iii. Open circuit

iv. Short circuit

v. Indeterminate

SELECT [ ¤ ] advances to the next detector channel ( multi-channel units only )

ENTER [ ↵ ] returns control to the main menu.

Open circuit status will also be caused by a loop inductance of greater than

e.g.

STATUS Chan : 1

( undetect )

1500uH 2000uH (typical).

Short circuit status will also be caused by a loop inductance of less than
20uH (typical).

895UM0001_02 DU100 User Manual Page 9 of 19

4.5 Time ( Time )

e.g.

Elapsed time ( in days and hours ) since the last reset/retune and the reason for the
reset/retune are displayed.

This information is particularly useful for detecting intermittent faults which are self­ healing.

Possible reasons for reset/retune include:

i. Reset: manual reset ( pushbutton ) or power failure

ii. Short circuit

iii. Open circuit

iv. Indeterminate

v. Inductance change of greater than 15 % ∆ L/L (typical).

SELECT [ ¤ ] advances to the next detector channel ( multi-channel units only )

ENTER [ ↵ ] returns control to the main menu.

10 D 5 H 1

( Reset )

895UM0001_02 DU100 User Manual Page 10 of 19

4.6 Crosstalk ( Xtlk )

First level screen awaiting first data capture.

e.g.

The channel to be stored can be changed by pressing the Select button if the detector
is a multi-channel unit. The frequency of the channel indicated in the top right hand
corner will be stored when the Enter button is pressed. This value becomes the
reference until the mode is cleared and re-entered.

The following menu will be displayed after the Enter button is pressed.

e.g.

Upon each successful data capture by the DU100 a result of the crosstalk will be
automatically displayed. If the same channel of the the same detector is re-captured
the test will fail as the result will be based on the original value.

e.g.

CROSSTALK 1

Store . . .

CROSSTALK 1

Test :

CROSSTALK 3

Test: PASS

CROSSTALK 2

Test: FAIL

895UM0001_02 DU100 User Manual Page 11 of 19

The test uses the original stored frequency and compares it to the new successful samples. If
the frequency is too close in proximity to the stored value, the test will fail.

SELECT [ ¤ ] advances to the next detector channel ( multi-channel units only )

ENTER [ ↵ ] returns control to the main menu.

This mode allows comparison of loop frequencies for potential crosstalk situations on
a pass/fail basis. The comparison can however be manually investigated, as described
under loop frequency.

Loops in close proximity to one another require a frequency spacing of greater than
2 kHz (typical) to avoid crosstalk (not necessary for channels connected to the same
multiplexed multi-channel detectors.

895UM0001_02 DU100 User Manual Page 12 of 19

4.7 Built In Self Test ( Test )

The function of the self test is to check the diagnostic unit’s functionality. The first
test will test the display and buzzer, the screen will blink with all characters flashing
and the buzzer being audible for this duration.

The next test is to verify that the EPROM ( the device which contains all the
diagnostic information ) is not damaged, the result being “PASS” or “FAIL”. Below
will be the checksum number of the EPROM which is used to verify the EPROM.

The next test is the RAM ( the device which contains all the working parameters and
received information from the detector ) and this test will ensure that the RAM has no
errors. The result of the test being “PASS” or “FAIL”.

The last line of information returned from the test is the version number of the
Diagnostic Unit.

The screen will then return to the normal operating mode.

Note: The keys will be disabled during the tests and restores upon the test being
completed.

895UM0001_02 DU100 User Manual Page 13 of 19

5. THEORY OF APPLICATION

5.1 Loop Frequency and Inductance Change

the vehicle detector. The operating frequency of the oscillator is determined by both
the physical characteristics of the loop and the frequency determining components
within the detector.

When a vehicle enters the loop, the loop inductance decreases causing a
corresponding increase in oscillator frequency. Experience has shown that the
percentage change of inductance ( ∆ L/L ) from an unoccupied loop to an occupied
loop is extremely repeatable for a given loop size and geometry, and for a given
location of the vehicle with respect to the loop.

• Loop size

• Loop depth below ground level

• Amount of residual metal in close proximity to the loop

Absolute loop frequency may be in the range of 12 kHz – 150 kHz. Change in
inductance, however, is vehicle and installation dependent. Its merit lies in
comparisons between various vehicles at a particular site or between various sites
with the same vehicle.

The relationship between absolute loop frequency and absolute loop inductance is
exponential in nature and is dependent on the particular detector type. Curves which
define this relationship are available on request from Nortech for a particular detector
type.

The inductive loop is energised by an AC signal which is produced by an oscillator in

When operated in “Loop” mode, the DU100 Diagnostic Unit displays both the
absolute loop frequency and the percentage change in inductance ( ∆ L/L ). For the
case of an unoccupied loop, the percentage change in inductance will remain at zero
( small values may occur due to oscillator or loop drift ). A vehicle traverses the loop,
the change in frequency and inductance may be observed.

The percentage change in inductance ( ∆ L/L ) is a measure of the sensitivity of the
loop detector installation. For a given vehicle, the value will be dependent on various
factors including:

895UM0001_02 DU100 User Manual Page 14 of 19

5.2 Loop Frequency Drift

This is a measure of the quality of loop installation. The display of drift value in
Frequency mode represents the absolute difference between the current loop
frequency and the reference loop frequency ( defined at the last reset/retune ).

Abnormal values of loop frequency drift can indicate a loop installation of poor
quality. Drift occurs primarily as a result of changes in ambient temperature and
should normally be less than 3%. Values significantly greater than 3% are generally
indicative of loops of poor quality. Potential causes include damaged insulation ( low
resistance earth path ), ingression of moisture and movement of loop wires.

Ingression of moisture also results in increased loop frequency drift. Capacitive
coupling exists between loop turns and the side walls of the loop slot as shown in
figure 4.1

Figure 4.1 - Loop capacitance coupling in roadway slot

This capacitance is directly proportional to the dielectric constant of the slot sealing
material. If this material is hygroscopic ( readily absorbs and retains water) or
incomplete ( does not fill the slot or encapsulate the wires ) allowing water to enter
the slot and penetrate between loop conductors, the capacitance will change greatly
due to the high dielectric constant of water. This change in loop capacitance will shift
the loop operating frequency thus causing loop frequency drift to increase.

895UM0001_02 DU100 User Manual Page 15 of 19

5.3 Detection Sensitivity

Detection sensitivity may be defined as the threshold level at which the smallest
change in inductance results in an output actuation. This is clearly dependent on the
inductive loop characteristics and may be adjusted by the sensitivity switch setting on
the detector itself.

With the detector set to maximum sensitivity, relatively smaller changes in inductance
result in detection. Detector sensitivity settings are designed such that maximum
sensitivity should be capable of detecting all vehicles while lower settings would
eliminate detection of bicycles, supermarket trolleys, and the over hang of high bed
vehicles.

Maximum and minimum values ( as shown in the DU100 sensitivity menu )
correspond to the largest and smallest changes in inductance resulting in detection
since the last time the detector was reset ( manual or power reset ).

The desired level of sensitivity may be achieved by comparison between recorded
changes and sensitivity switch settings at a particular site.

Over a process of time, the minimum value which will approach the demanded
sensitivity threshold of the detector, thus confirming this selection.

To reliably determine which sensitivity level should be used at any particular site, the
sensitivity level of the detector should be set to maximum ( to ensure that all vehicles
are detected ). A variety of vehicles matching the types used on the site should be
driven over the loop to determine the level of change. The vehicle with the lowest
change ( on the “MAX” level of the DU100 sensitivity menu ) should be used to then
determine the sensitivity threshold of the detector. A threshold more sensitive than the
observed change should be selected.

If a particular vehicle was to be excluded (e.g. supermarket trolley ) then the threshold
level selected on the detector would be less sensitive than the maximum change
recorded for the vehicle.

5.4 Detector Status

the Diagnostic Unit takes the samples.

Detector status may be defined as the current state the detector is operating in when

The first event that will occur after the detector is powered or a loop is connected
( and the Diagnostic Unit is receiving data ) is that the detector will begin to tune
( Tuning ). During this time the detector will determine the operating frequency of the
loop connected and most suitable operating parameters to be applied to the loop.

895UM0001_02 DU100 User Manual Page 16 of 19

Thereafter the detector will change to the undetect ( Undetect ) state. During this time
the detector will monitor the loop for vehicles, as well as determine the temperature
changes around the loop and detector and adjust the levels accordingly.

Upon a vehicle entering the loop and the threshold levels for detect being correct, the
state then changes to detect ( Detect ). The detector will then monitor the vehicle as it
passes over the loop. It will continuously monitor the vehicle until it leaves and reverts
the state to undetect. ( Undetect ).

If the loop connected to the detector was disconnected or shorted due to failure, the
detector would immediately log this occurrence and change states to loop fault ( Loop
Fault ). The detector will then determine the characteristics and nature of the fault and
wait for the problem to be corrected.

5.5 Historical Fault Data

Historical Fault will display the last recorded fault by the detector as well as the time
elapsed since the last fault. If no fault has occurred during the detector’s operation, the
fault status will be “RESET” and the time displayed will be from the time the detector
was last powered up or the reset push button was pressed.

If a loop fault occurs then the fault will be recorded and the elapsed time since the
fault occurred to the current time will be displayed to the nearest hour. Even if the
loop fault no longer exists the event will remain until the next fault occurs. The loop
fault will be displayed as either “Short Circuit” or “Open Circuit”. An open circuit
indicates that the loop has been disconnected ( wire continuity broken ). A short
circuit indicates that the loop has been shorted at some point.

895UM0001_02 DU100 User Manual Page 17 of 19

5.6 Crosstalk Prevention

When two or more loop configurations are in close proximity, the fields of one loop
can interfere and disturb the field of another. This phenomena, known as crosstalk,
can cause false detects and cause the detector to lock-up and no longer function. The
problem also exists when reinforcing used to strengthen a structure is in close
proximity to the loop. It provides an efficient means of coupling two loops together.

Crosstalk can be eliminated by following a few simple steps:

• Always ensure separation between loops when planning a new site. Where
possible ensure a minimum distance of 2 metres between loops.

• When using non multiplex detectors, change the number of turns between adjacent
loops by one or two turns, if a number of loops are being installed.

• When reinforcing is present, the number of turns should be increased by two or
more to compensate for the loading effect of the loop caused by the reinforcing.
There will be a loss in sensitivity. The loop should also be mounted as far from the
reinforcing as possible, typically 150mm. Care should be taken to ensure that no
loop cable is exposed after sealing compound is applied.

• The loop feeder should ideally be a twisted pair with a low series resistance so that
the feeder does not reduce sensitivity. The twisting of the feeders is especially
important as this will counteract the effects of noise and crosstalk form adjacent
feeders and power cables. Typical twists are greater than 1 turn per 3 centimetre.
( 33 twist per metre ).

• Once detectors have been connected and powered up the loop frequencies must be
measured to check frequency separation between loops. When only one multiplex
detector is used, this does not need to be done. If more than one detector is used
this is crucial. Record the frequencies and check that there is at least 2000Hz
separation between all loops in close proximity to one another. Note that this
situation can be severely aggravated by the presence of steel re-inforcing below the
road surface.

895UM0001_02 DU100 User Manual Page 18 of 19

6. Appendix A – Typical Values

Detector
Model

Frequency of
Operation

Inductance Change
%∆L/L

Drift

Sensitivity %∆L/L

MAX

Typical 20KHz 150 KHz

Parking
Detectors

Traffic
Detectors

MIN MAX MIN

0.02 %∆L/L 6 %∆L/L

12KHz 85KHz

15KHz 140KHz

0.02 %∆L/L 6%∆L/L

0.02%∆L/L 6%∆L/L

before
retune

MAX

less

than

3%

3 %

3%

MIN MAX

0.02 to 0.5 %∆L/L 0.03 to 6 %∆L/L

0.02 to 0.5 %∆L/L 0.03 to 6%∆L/L

0.02 to 0.5 %∆L/L 0.03 to 6%∆L/L

895UM0001_02 DU100 User Manual Page 19 of 19