Data acquisition, transmission and processing. Survey networks

5 DATA ACQUISITION, TRANSMISSION AND PROCESSING. SURVEY NETWORKS 

Data processing. The microprocessor functions according to the program stored in the programmable read-only memory (PROM), a solid-state data-storage device whose contents is virtually indestructible. The main tasks of the 8-bit microprocessor are (a) control of the input multiplexer (b) start and control of the calibration cycle (c) correction of measured values according to the results of the calibration cycle (d) computation of periodic averages (e) calculation of output data (f) output of data and (g) control of peripherals. 

Output of control signals to the monitor. Up to three control signals can be sent to the pollution monitors via the digital output control. One of these signals is the calibration cycle control signal. 

Timing. An accurate, real-time digital clock is used for timing all events. At the heart of the digital clock is a crystal whose output is used to derive the minute, hour and day signals. From these, the microprocessor obtains the months and years. 

Protection against loss of data due to power failure. The microprocessor and digital clock are provided with reserve power supplies, which ensures that, if the normal mains supply should fail, the timing continues uninterrupted and there is no loss of data from the RAM. After restoration of the normal supply following a power failure, the time, date and stored data are recorded by the output equipment and normal automatic operation is resumed. Recharging of the reserve power-pack also takes place when the operation from the mains supply is restored. No reserve supply is required by the PROM, whose memory contents are unaffected by disturbances to the mains. 

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