AWOS Automatic Weather Observation

  • readac.jpg


  • Aviation-usable data
  • Auto or manual operation
  • Multi-processor design
  • Surge and EMI protection
  • Modular for easy expansion
  • Operator interface
  • Self diagnostic package
  • -40C to + 50C operation
  • No power-down required to change modules

Detailed Description


The AWOS (Automatic Weather Observation System), formerly known as READAC (Remote Environmental Automatic Data Acquisition Concept), system was developed by the Atmospheric Environment Service of Canada through a contract to Bristol Aerospace Limited, to meet the accurate and reliable needs of general aviation weather data collection.

The weather station is capable of fully automatic or manual operation or a combination of both.

A modular design approach has been implemented in this fifth generation auto-station. A fully modular hardware bus architecture approach coupled with multi-layer protocol software heralds the arrival of a system insensitive to electronic changes.


The significant advantage is of two fold importance:

  1. As electronics technology improves over the years, these innovations can be reflected in new modules with no negative impact on existing field units.
  2. Existing stations can be user-modified, either through addition or deletion of modules, to change the configuration without software modification.

All of these changes can be made without powering down the station and with no risk of EMI (electro-magnetic interference) generated problems. The AWOS systems are designed with a complete multiple redundancy EMI protection system at the module, shelf and bus levels.


An AWOS field station consists of four classes of modules, being shelf controller, communication controller, peripheral interfaces and service modules. All modules have been designed for low power, wide temperature and high reliability operation.

The Shelf Controller (SC) is the heart of all AWOS stations. Its function is to collect and route from the Peripheral Interfaces (PI's) to the Communications Controller (CC). The SC does not process any sensor data. In this way, neither the growth of a station nor the types of PI's in it, is restricted due to the shelf controller.

The Communications Controller (CC) handles local data storage and monitoring plus specific communications media (i.e., Goes satellite, VHF radio, landline/telephone etc.) Operator command sequences include poll simulation, data monitoring, communication line monitoring and real time maintenance work through diagnostic messages.

The Peripheral Interfaces (PI's) perform more complex and varied tasks than ordinary sensor interface modules. They perform sensor interfacing, data processing and inter-module communication functions. All data sampling and data conversion processes are resident in each module. Every sensor type has its own module to assure functional modularity in station composition, operational maintenance and problem free station expansion.

Other than the possible need of an external power source, a sensor's needs are totally met by its PI. Each PI outputs both raw and processed data onto the data bus. If a complex peripheral needs data from another sensor to develop its data, it simply pulls raw data from the bus. This inter-module data transfer is totally transparent to the shelf controller, and forms the basis of the multiprocessor architecture.

The service modules include units such as the solar power supply module and the 110 volt power supply module.

Weather Data Types

An AWOS station can provide any combination of these data types:

  • wind (speed, direction and gust)
  • total precipitation
  • single or dual atmospheric pressure
  • altimeter setting
  • dewpoint temperature
  • visibility

In addition, Valcom has other modules for cloud height, etc., in development.

Test Set

The AWOS test set is a sophisticated, self contained portable unit which gives the operator complete access to all AWOS modules. The test set can be used for data monitoring, module diagnosis, setting of the shelf control real time clock and generating an emergency message for broadcast.

Operations of the test set are fully user-oriented with touch sensitive function key switches and instructional prompts on the display. It also has enhanced test mode for use with the various peripheral interface modules, all interfacing cables are conveniently stowed in the test set. The electronic and control console for the test set are packaged in a rugged metal attache case for ease of transport.

Sensor Simulators

A complete line of sensor simulators is available to support both initial installation and check-out activities and operational function tests. The units are small, lightweight and easy to connect to the appropriate module using the attached interface cable. The simulators allow an operator to conduct a complete evaluation of the AWOS hardware and software, independent of actual sensors which may be at fault.

Table Specifications