Access Control and tracking System for Hazardous Areas

• Personnel tracking and protection
• Vehicle tracking and identification
• ATEX certified for M1 and Group 11B
• ATEX approved for hazardous dust environments to Zone 20
• Multiple transponders can be read

Introduction

Davis Derby has developed a radio frequency based access control and tracking system for hazardous areas using Identec Cryptag technology. The system is ATEX certified for use in hazardous areas for mining and petro-chemical industries. The system is also ATEX approved for areas where explosive dust creates a hazard.

The system comprises three components:

• Compact radio frequency intrinsically safe transponders
• A quartz filled EEx electronic reader unit
• A range of EEx M ATEX approved antennas

Applications

Applications include man-power tracking and deployment, personnel protection, vehicle tracking and fuel loading and discharging systems.

System Components

Intrinsically safe transponders

The miniature intrinsically safe personnel transponder is certified for Group I and Group II, it is an active device, containing a lithium battery to ensure maximum range can be achieved. The battery has a life of 5 years based on being read for 10 minutes per day. The transponder sends a battery low warning when it is almost discharged.

The tag data is stored using a secure 32 bit code, which once programmed cannot be changed.

The transponder measures 86mm x 56mm x 6.5mm thick.

Reader Unit

The mains powered reader unit is housed in a stainless steel sand filled EX q type enclosure, it has an Ex e terminal chamber and intrinsically compartment for the PC 21 CAN bus interface. It has intrinsically safe switch inputs, opto-coupled digital outputs and a CAN bus data link. The certification concept is EX ia e q IIB for group II and EX ia e q I for group I.

The reader can drive up to 4 Antennas which are sequentially scanned by the Antenna Multiplexer board. In its basic form the reader unit is fitted with only one Antenna, in which case the Multiplexer board is not fitted.

The reader is fitted with a CAN bus data link, this can be a high speed link running at 125 kb/s at distances of 500 metres, which connects to a CAN bus cluster typically comprising of the Davis Derby Group I MineWATCH PC 21 modules, there can be up a total of 8 modules connected to the CAN bus cluster. Alternatively it may be a CAN bridge low speed data link operating at 10 kb/s at distances of up to 5 km. The CAN bridge option allows connection to a computer via a suitable Davis Derby interface unit.

The reader unit has 8 intrinsically safe inputs derived from voltage free switch contacts. There are also 6 segregated opto-coupled outputs designed to interface with other intrinsically safe equipment. The reader unit has an intrinsically safe compartment containing the PC 21 –1 – R module and the associated terminals. The unit is equipped with diagnostic led’s which are visible through a window in the intrinsically safe compartment.

Antennas

Davis Derby has developed a range of Antennas for various applications, these are ATEX certified for Groups I and II to category EX m.

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