Territory Stories

Electronic Data Collection and Analysis System



Electronic Data Collection and Analysis System


Yin Foo, Des; Foley, Margaret


E-Publications; PublicationNT; E-Books; Report ; 39/1992




Made available via the Publications (Legal Deposit) Act 2004 (NT).





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Power and Water Authority

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Report ; 39/1992

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Technical Report WRD92039 Viewed at 15:07:17 on 29/07/2010 Page 106 of 192. 43 gauge transducers and vented cable be employed. Indeed thiS is the opUon chosen by most pump test practitioners and PAWA staff may consider that a system should be set up specifically for these condJUons if they are connnon enough. However. with water depths as great as 110m. and. even for shallow water depths. with drawdo"ms over 30m not uncommon. I have been warned ollen enough about the problems associated ,vlth inefficient cable venting (either on its own or through heatL'lg of the cable or damage to it! to conclude that a gauge pressure transducer carmOl be gu~ranteed to work in such conditions every time It is employed. Besides this. the cost of vented cable will become excesSive unless a mechanism is set up to vent it down the hole and use unvented cable the rest of the way to the surface. However such a downhole vent cannot be guaranteed never to dog and. where large drawdowns are expected (for example 5Om). vented cable length may still be unacceptably large. Hence I recommend that absolute pressure transducers be employed. As was discussed earll'or, the penalties in uSing absolute sensors are that a barometer must be purchased, software must be written to correct readings. and system accuracy "rill be cut by a fa.ctor of. at most. 2. Centralized or Decentralized Logging: Here the choice is between a single logger with a large number of charmels which colleels water level infornlal.ion from all the bores as well as flow rate and water quality information, or a system comprie,ing a number of loggers located at strategic sites such that transmission cable lengths are kept short. I prefer the latter system for a number of reasons. Firstly conunllnlcatJons to distant observation bores are certain to be broken often by vehicles, animals and people. Secondly. although some multichannel loggers are cheaper than a number of Single charmel loggers (here, too. il depends on the make), signal transmission would need to be by current if multichannel loggers were used. As only the n10re e.'(pe~lSive dovtlnhoIe transducers are able to traIlsmit current. these would need to be employed, or an uphcle transmitter would become necessary to convert a frequency or vollage signal prOVided by a cheaper transducer to current for transmissIon to the logging site. In either case the cost advantage of a centralized system would be diminished. A disadvantage of the d'~cenlralized system is that increased software complexity may be necessary to collate nll the data, but this Is, in principle, not difficult and does not. in my opinJon. outweigh the advantages of decentralized logging. i

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