Oct/Nov 2006

ZigBee low-powered machine-to-machine wireless technology, a relatively new standard, has been harnessed by telematics specialist CMS Global Technologies for an enhancement to its trailer tracking system. It says the system offers particularly precise and detailed real-time temperature monitoring.

The company is pitching it particularly at operators needing to meet the latest legislative requirements for tracking the temperature of goods throughout the delivery cycle. It says the system meets the relevant British quality standard (BS EN 12830:1999).

ZigBee requires very little power - no more than the amounts delivered by "fit-and-forget" batteries sometimes used in trailer tracking systems; yet theoretically it can transmit data up to 250ft.

In the CMS implementation, sensors monitoring individual load compartments in refrigerated bodies are each equipped with a ZigBee transmitter, and send temperature information wirelessly to a central "black box" monitoring unit in the truck cab, which is set up to sound alerts if temperatures pass out of a predetermined range.

 

The black box is also equipped with conventional GPS/GSM technology to track the position of the trailer and transmit that information, along with temperature and other details, to a central CMS server. From here, the operator can look up the information on the Internet.

Accuracy and security have been given special attention. CMS says the sensors have a measurement range from minus 50 deg C to plus 110 deg C. They are encased in enclosures offering protection to IP67, and comply with EN61010-1, EN50081-1 and 50082-1. Resolution is said to be plus or minus 0.1 deg C, and accuracy better than plus or minus 0.5 deg C.

The sensors record temperature every minute, but the interval is programmable up to 18 hours. Every sensor reading is time-stamped with the absolute time (UTC) maintained in a real-time clock that is set from a GPS receiver, and these times cannot be altered.