Reference Number: INTAS-97-0606
INTAS logo Development of an Intelligent Sensing Instrumentation Structure I.S.I.S.
System Design of ISIS
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Features of ISIS higher level | The implementation of ISIS units
The implementation of ISIS units
1. The Measurement Module The developed Measurement Module is a simple implementation the lower and middle level of the general ISIS structure. It can select and process the output voltage amplitude output signals of 15 sensor and the pulse width output signals of 10 sensors. It can also control an External Instrument equipped with an RS485 communication port. The Measuring Module structure is presented on Figure 5.

Figure 5. Measuring Module
The ADCs and multiplexers constitute the lower level circuitry. The module is controlled by two MC68HC705C8A microcontrollers (mCs). The Lower mC is responsible of receiving the ADC's outputs and calculating the pulse width of the multiplexer's output signals by the use of its internal timer. It then validates the measurement results using comparison parameters stored at the modules EEPROM. The Middle mC gets the measurements from the Low mC, calculates the result of the function (where the Ai and Bi parameters are also stored at the EEPROM) and stores the results. This microcontroller is also responsible for the management of the Data Bus messages, which are of three types: request of measurements, request of module parameters (stored on the EEPROM) and readjustment of module parameters (write to EEPROM).
2. The Portable Tester Figure 6 presents the Portable Tester, consisting of a 12-button telephone type keypad, a 2-lines 20-characters LCD, an MC68HC705C8 microcontroller and a TTL\RS485 converter. The user sends commands to the system and views the retrieved data on the LCD.

Figure 5. The Portable Tester