1. Hydrological Services Pty Ltd Sydney, Australia Bill Barratt CEO AHA Conference July,04 © Copyright

2. Old Vs New -40 o C Float Wells History Of Gas Purge System © Copyright

3. Skeppsholen Maregraph Continuous Water Level Records Since 1755 © Copyright

4. Skeppsholen Maregraph cont © Copyright

5. Skeppsholen Maregraph cont Late 1700s These Records Were Used To Show That The Swedish Land Mass Was Rising About 50 mm Per Year © Copyright

6. Skeppsholen Maregraph cont In 1765 Mr Celsius Commenced Air Temperature Measurements At This Site © Copyright

7. Float Well IN SWEDEN FLOAT WELLS OPERATE IN TEMPERATURES DOWN TO –40 o C. THERE ARE TWO TYPES OF FLOAT WELLS: 1.HEATED FLOAT WELLS 2.UNHEATED FLOAT WELLS © Copyright

9. Heated Float Well 380 VAC Power. Hut Temp +10 o C. Air Heater. Air Blower In Well. Heating Element In Inlet Pipe. © Copyright

10. Heated Float Well Cont © Copyright

11. Unheated Float Well © Copyright

12. Gas Purge Systems © Copyright

13. Gas Purge Systems Cont Developed By Dutch Engineer Late 1940s Adopted By U.S. State Of Illinois Water Group in 1954. (Re: Bubbler System Instrumentation For Water Level Measurements, By Gerald H Nelson, 1954) USGS Australia, Des Sherlock Late 1950s © Copyright

14. Gas Purge Systems Cont Early Instruments: Miriam Site Glass Bubble Units Bottled Dry Nitrogen or CO 2 Exactel Servo Manometers U.S.G.S Servo Manometer ( In Australia known As Stevens) © Copyright

15. Gas Purge Systems Cont AUSTRALIA: Qld Developed Their Gas Electric Manometer To Get A Larger Range In Late 50s Des Sherlock Developed The Sherlock Pressure Sensing Unit 1965-68 Using The Force Balance Principle. GCO, For Use With Gas Purge Or As A Fixed Open Bell System. © Copyright

16. Gas Purge System Cont © Copyright

17. Gas Purge System Cont © Copyright

18. Gas Purge System Cont Force Balance System More Accurate, It Measures Water Level Direct Others Measured Mercury level Changes -A Factor Of 13.7 © Copyright

19. Gas Purge Systems Cont 1972 Sherlock & Holmes Paper On P.S.U. In Germany Next Year A U.S. & A Germany Copy Were Marketed Neither Achieved P.S.U. Accuracy Or Reliability © Copyright

20. Gas Purge System 1978H.S. 50 Metre Model Built For Dam Storage levels 1982H.S. Found HS-22 And Miriam Bubble Units Were Unstable At Bubble Rates Lower Than 80 Bubble/Minute © Copyright

21. Air Compressor System 1982-1988H.S. Developed New Differential Regulator Stable At Bubble Rates From 5 B/Minute to 200 B/Minute 1989Dry Bubble Unit (No Sight Glass) Early 90sParascientific Developed High Resolution Dry Pressure Transducer Accuracy Similar To PSU. Mid 90sGas Purge Compressors First A Company In New York Then a UTAH And French Co. © Copyright

22. Air Compressor System Cont © Copyright

23. Air Compressor System Cont 1998-H.S. Had A Contract To Supply 28 Units To a Sth. East Asian Country -Intended To Buy In And Re- Badge -On Testing None Would Operate To Our Requirement -In Six (6) Weeks We Developed HS-55 © Copyright

24. Air Compressor Systems Air Compressed Water Is Produced Must Be Dried After Compressing H.S Only Manufacturer In The World To Do This. © Copyright

25. Air Compressor System Cont © Copyright

26. Air Compressor System Cont Range Water Level0-30 Metres River LinesUp To 200 Metres Operating Temp-30 to +70 o C Humidityup to 100% © Copyright

27. Air Compressor System Cont 1998-2004 Proliferation New Models With Small Capacity Gas Storage Tanks New Type Instantaneous Purging Compressor Most With Inbuilt Pressure Transducers. None Dried Air After Compressing It Unreliable In High Humidity Conditions Moisture In River Line Insufficient Storage And/Or Compressor Capacity To Purge River Line Dry. © Copyright

28. Air Compressor System Cont At H.S. From 1984 Experimented With Pressure Transducers Technology Wasnt Until 1998 We Saw Possibility Of Making A Pressure Transducer With Similar Accuracy As The PSU I Visited Druck In U.K. In 1998 Negotiated Supply Of O.E.M Strain Gauge Modules Druck Advised Us On Processing These Elements – Remove Initial Drift – Stabilise Output © Copyright

29. Air Compressor System Cont H.S. Developed Signal Process – Initially 4-20 mA Output – Then Voltage – Now RS232 & SDI-12 © Copyright

30. Air Compressor System Cont 23/7/04 WL3100 Firmware To Accept Inputs – Latitude – Altitude – Average Water Temperature – Height Of Instrument Above Orifice And User Factor Is Calculated To Adjust Our Factory Calibration To Any Site In The World. This Is Similar To What Parascientific Do We Now Feel We Have A Pressure Transducer With Equivalent Accuracy To Our PSU However, It Will Not Have Longevity Of PSU © Copyright

31. Gas Purge Compressor Cont © Copyright

36. New Technologies © Copyright

37. Conclusion