Abstract:
This thesis presents the design and construction of an analog data acquisition system for measuring and recording analog signal, controlled by a microprocessor. The system has an accuracy of 0.1 percent of full scale. It can be connected to several types of transducers and can handle up to a maximum of 240 transducers. The transducers are scanned with a rate of 0.1 second per transducer. The obtained data are saved in memory and can be reviewed at any time. The microprocessor system which controls the internal operation consists of a Z-80 8 bit microprocessor, 8 kilobytes of ROM and 2 kilobytes of RAM. The sampled analog signal is converted into a 12 bit digital signal. The display unit has 8 digits of 7-segment LED. When the measured value exceeds the set valve, the system will sound an alarm and energize the relays. The scanner may be located near the transducers to ease the wiring problem. The other interfacing circuits are clock unit, keyboard, printer and RS-232C to communicate with other microcomputer systems. The measurement data are printed by the printer at specified time interval. The constructed unit can be used for measuring and recording temperature in the range -200 ℃ to 200 ℃. It can be connected to 30 transducers. The transducers are type CA thermocouples and type Pt -100 resistance bulbs. The system has been tested and proved to have an accuracy better than 0.1% of full scale.