Nortech PD27 Series - User Manual

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Overview

Function Description
Important Technical Specifications
Functional Data
Electrical Data
Environmental Data
Mechanical Data
Approvals
Usage Features
Installation Guide
Maintenance Features

The PD27x Series Dual Channel Inductive Loop Vehicle Detector is a microprocessor-based detector designed for parking and vehicle access control applications, particularly suited for complex multi-lane access control and counting. Its primary function is to detect vehicle presence by sensing inductance changes caused by a vehicle passing over a buried wire loop.

Function Description:

The detector operates by sensing a small reduction in the inductance of a loop when a vehicle passes over it. This triggers its output relays, which can then be used for various control functions. It features fully automatic tuning with an option for Automatic Frequency Selection (AFS), which allows the detector to evaluate all five frequency bands and select the best operating frequency. When AFS is off, the frequency can be selected manually. The unit is designed to eliminate crosstalk between loops connected to the detector through sequential channel scanning.

The PD27x can be configured for different output types:

Presence on Detect: The relay provides a continuous output for the entire duration a vehicle is detected over the loop.
Pulse on Detect: The relay outputs a 150ms pulse when a vehicle is detected.

It also offers two presence methods:

Permanent Presence: Maintains vehicle presence detection by continuously compensating for environmental changes, suitable for safety-critical situations where detection must persist until the vehicle leaves the loop.
Limited Presence: Limits the duration of vehicle presence over the loop, used for statistics or control where a parked vehicle should not impede continued operation. A 1% ΔL/L detect typically times out after approximately 1 hour.

The detector includes AB Logic, which can be used for directional counting. A transition from loop 1 to loop 2 (forwards) results in a 150ms pulse on Relay 1, while a transition from loop 2 to loop 1 (backwards) results in a 150ms pulse on Relay 2.

Important Technical Specifications:

Functional Data:

Tuning: Fully Automatic, with optional AFS.
Self-tuning range: 20 μH to 1500 μH.
Sensitivity: Four steps adjustable via DIP switches (High, Medium-High, Medium-Low, Low). Options: 0.01% ΔL/L, 0.02% ΔL/L, 0.05% ΔL/L, 0.10% ΔL/L.
ASB (Automatic Sensitivity Boost): Selectable via DIP switches. Boosts sensitivity to maximum on detection and maintains it until the vehicle leaves the loop.
Frequency: Operating frequency of 18 - 110 kHz (determined by loop geometry and frequency setting). Five possible frequencies with AFS on, four selectable options with AFS off.
Output Configuration: 2 output relays, user configurable for presence or pulse on detect.
Pulse Output Duration: 150ms.
Drift Compensation Rate: Approx. 1% ΔL/L per minute.
Response Times: Detect: 53.0 - 73.0ms; Undetect: 280.0 - 350.0ms.
Surge protection: Loop isolation transformer, gas discharge tubes, and Zener diode clamping on loop input.
Power Fail: Infinite memory retention of detector state on power failure, provided certain criteria are met (detect level > 0.8% of sensitivity, temperature change < 20°C, no fault with AFS activated, vehicle presence > 1 second before power loss).

Electrical Data:

Power requirements:
- PD271: 120V AC ± 10% (48 to 62Hz), 1.5 VA Maximum @ 230V.
- PD272: 230V AC ± 10% (48 to 62Hz), 1.5 VA Maximum @ 230V.
- PD274: 12-24V ± 10% DC/AC (48 to 62Hz), 1 VA Maximum @ 12V.
Relay Contact Rating: 2A@30VDC, 0.5A@125VAC, 0.25A@250VAC. De-rating applies above 60°C.

Environmental Data:

Storage Temperature: -40°C to +80°C.
Operating Temperature: -40°C to +80°C.
Humidity: Up to 95% relative humidity without condensation.
Circuit protection: Conformal coating over PCB and all components.
IP Rating: IP30 (must be installed in an enclosure).

Mechanical Data:

Housing Material: ABS blend.
Mounting Position: DIN rail mounting and Shelf.
Connections: 11-pin Submagnal (JEDEC No. B11-88) OR 2x 6 way Plugs on DIN Rail Mount.
Size of Housing: 78mm (High) X 41mm (Wide) X 80mm (Deep).

Approvals:

CE Regulations: EN 301 489-3 (Equipment Type: III, Class of Equipment: 2), CISPR22, EN 50293 (Performance Criteria B).
Safety: IEC/EN 60950-1.
FCC Advisory Statement: Complies with Part 15 of FCC Rules.

Usage Features:

Hardware Setup: Designed for DIN rail mounting, with controls and visual indicators at the front and wiring at the rear. Power, loop, and relay outputs connect to an 11-pin relay base.
DIP Switch Selections: Used to configure presence mode (permanent/limited), pulse/presence on detect for each channel, fail-safe/fail-secure relay output polarity, AB Logic, Automatic Sensitivity Boost (ASB), and Automatic Frequency Selection (AFS).
Frequency Selection: Switches (1 and 2) allow shifting the operating frequency to prevent crosstalk between adjacent loops when multiple detectors are used.
Sensitivity Selection: Switches (1 to 4) adjust sensitivity from 0.01% to 0.1% ΔL/L.
Push Button (Retune and Powerfail):
- Holding for 3 seconds initiates a detector retune.
- Holding for 10 seconds determines Powerfail status (LEDs ON = Powerfail ON, LEDs OFF = Powerfail OFF).
- Holding for 30 seconds toggles Powerfail status.
Front Panel Indicators:
- Red Power / Communication LED: Indicates power and functionality, also used for communication with DU100 / DU700 diagnostics.
- Green Channel LED: Indicates channel status (Idle, Detect, Tuning, Fault). Flashes at 2Hz for tuning attempts or self-healing faults, 1Hz for historical faults.

Installation Guide:

Product Safety Requirements:
- Unit MUST be grounded (earthed).
- Disconnect power before working on the unit.
- Installation and operation by service personnel only.
- No user serviceable parts inside; warranty void if cover removed.
- Suspend traffic during installation and testing in barrier areas.
- For 120 VAC and 230 VAC models, a readily accessible disconnect device must be incorporated into mains wiring (EN60950-1:2005 Section 1.7.2.2).
- Power supply MUST have short circuit and over current protection (e.g., 5 Amp Magnetic Circuit Breaker for AC, fuse for DC).
- Product must be installed in an enclosure (IP30).
- Only use CE approved 11-pin relay bases (Nortech Part No. CTR119090 or equivalent).
- Nortech 11-pin wiring harness (Part No. 302FT0041) can be used for SELV voltage applications (<60 VDC or <42 VAC).
Environmental Factors: Must be installed in a housing/fire enclosure to protect from environment. Rate of temperature change MUST not exceed 1°C per minute. For outdoor installation, refer to Appendix B.
Crosstalk Prevention: Sequential polling eliminates crosstalk between loops on the same dual-channel detector. For different detector modules, ensure adequate spacing (approx. 2 metres), different frequencies, screened feeder cables (earthed at detector end only), and separate feeder cable slots (at least 300 mm apart).
Reinforcing: If reinforced steel is present, add 2 turns to the loop. Maintain minimum 150mm spacing between loop/cable and steel.
Loop and Feeder Material Specification:
- Silicone insulated cable preferred over PVC.
- Stranded copper conductor (minimum 1.5 mm² cross section) preferred over solid wire.
- Feeder should be twisted (minimum 20 turns per metre) to minimize electrical noise.
- No joints recommended in loop or feeder; if necessary, solder and terminate in a waterproof junction box.
Sensing Loop Geometry:
- Circumference: Max 30 m.
- Area: Max 30 m², Min 1 m².
- Rectangular shape, longest sides at right angles to traffic movement, ideally 1 metre apart.
- Loops for direction logic can share a common slot, max 1 metre separation.
- Feeder length: Max 100 metres (shorter is better for sensitivity).
- Loop turns: 2 turns for >10m circumference, 3 turns for <10m, 4 turns for <6m. Construct adjacent loops with alternate 3 and 4 turn windings.
Loop Installation:
- Cut slots in roadway (4mm width, 30-50mm depth).
- 45° crosscut at corners to reduce damage.
- Continuous loop and feeder cable.
- Seal loops with "quick-set" black epoxy compound or hot bitumen mastic.

Maintenance Features:

Customer Fault Analysis: Provides a table for fault finding, including symptoms (e.g., Red LED off, Green LED flashing, intermittent output), probable causes (e.g., faulty power, loop connection, crosstalk, shorted loop, low sensitivity, loose connections), and remedies (e.g., check power, diagnostics, retune, change frequency, check wiring, Megger test).
Functional Test: Connect to an inductive loop (approx. 300 microhenries). Use a small metal object to check detection (output LED lights, relays operate). For sensitivity and presence time checks, use a calibrated tester with a movable vane.
On-board Diagnostics: Obtainable using DU100 / DU700 units for comprehensive analysis of operating characteristics.
Technical Support Form: Provided for recording installation details and requesting technical support, aiding in identifying changes and resolving problems.