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).
Power and Water Authority
Report ; 39/1992
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Technical Report WRD92039 Viewed at 15:07:17 on 29/07/2010 Page 108 of 192. 45 For more distant observation bores I suggest that the much cheaper Westdata transducers together with their submersible loggers be used. The specifications are good. the cost Is very low and electrical interference should not be a problem. The disadvantages of this alternative \vJ.Il be discussed below under "loggers". It should be noted that \!.1.th the use of \Vestdata systems down the observation holes the case against gauge sensors Is not S<l strong. This Is bt!cause \Vestdata vented cable Is very cheap ($1.68 per metre) and better vented than most: also it Is only slightly thicker than their llIIvented cable and hence only marginally more cumbersome. In this case cable cheapness does not cause problems ,,1th signal quality because the signal Is digital and hence. while moisture ingress may alIect its amplitude. it will not alIect its "message" unless mOisture Ingress is excessive. Flowmeter It Is probable that PAWA staff are in a better position to make this chOice Lllan I am because of their greater experie;:lce in flow measurement ",,1thL'l the pump test context. With some reservatlons I suggest using the Signet 8500 paddlewheel flowmeter. The main advantages of this unli. are that it Is cheap. appears to be quite robust. Is battery powered and transrUlts 4-20 rnA current. Also. a particular sensor can be used on a variety of pIpe Sizes though. unfortunately, no one sensor can be used across the entire range of pipe si7.es employed by the PAWA (ranges are 1/2 - 4 lnehes. 5-8 inches and lO-up inches). The disadvantages of this .lnstrument are the possibility of abrasion of the paddlewheel. the possibility of bearing deterioration. and the fact that the measuring range is only 20:1 in a particular flow setting. If thiS instrument were used. it would be lmportant that discharge orilke plate manometer readings be lnterrnlttently recorded for both In-test callbration of the flowrneter. and to monitor any change in the latter's characteristics. over time. If this alternative is not chosen then I would consider further the Great Lakes Instruments insertion paddJewheeJ sensor marketed by Combined Instruments. the Kent 3000R helical vane flOWI::leter (with or ,,,ithoul. the rateof-flow lndlcatorl. the Signet "Mighty Mag" magnetic flowmeter or the Kent VEe magnetic flowmeter. Again. whatever instrument is chosen. the discharge Orifice plate should be retained in case of flo .... 'meter malfunction and as a check on 110\\1meter calibration. Also, depending on the type of flowmeter chosen. it may be desirable to adJ:Jsl Ihe span and zero of the electrical output as soon as the pump L., switched on so that th,! logger Is able to record flow rate variations with a high resolution. If this is the case. the manometer may be needed to set flow rate correctly upon the pump being sv.1tched on.