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Manual – Precision Water Level Instrument

Unidata Manual 6293 - Precision Water Level Instruments Issue 2.1

Picture of the Water Level Instrument

Summary of Contents for 6541

Page 1: ...41 Precision Water Level Instruments Issue 2 1 2007 AB CB JH MS KC Copyright Unidata Pty Ltd 2000 2008 All rights reserved No part of this publication may be reproduced transmitted transcribed stored...

Page 2: ...Manual Precision Water Level Instrument Unidata Manual 6293 Precision Water Level Instruments Issue 2 1 Picture of the Water Level Instrument...

Page 3: ...LATION 14 4 1 CONTROLS AND SETTINGS 14 4 2 CONNECTING A BATTERY PACK 14 4 3 CONNECTING TO AN EXTERNAL DATA LOGGER VIA HSIO 15 4 3 1 HSIO Interfaces 16 4 4 CONNECTING MORE THAN ONE INSTRUMENT TO A LOGG...

Page 4: ...DETAILS OF UNIDATA FLOAT SYSTEMS 34 9 1 FLOAT LINES 34 9 2 FLOATS 34 9 3 FLOAT PULLEYS 37 9 4 FLOAT SYSTEM ACCESSORIES 37 10 APPENDIX C FLOAT SYSTEMS 38 10 1 INTRODUCTION TO FLOAT SYSTEMS 38 10 2 SOU...

Page 5: ...t The instrument is normally connected to the water surface by a float system As the water level changes this rotates the input shaft on which is mounted an optical encoder The encoder is continuously...

Page 6: ...all captured in measuring tanks long term precipitation data Evaporation from measuring pans automatic evaporation monitoring The float pulley can be changed to vary the units and resolution of the me...

Page 7: ...m an external power source HSIO Access to a 4 wire plus ground Unidata HSIO interface is provided by the front panel terminals A data in terminal allows extension of a HSIO instrument chain SDI 12 The...

Page 8: ...setting cannot be used for HSIO please use 5 SDI 12 instead Note 2 Pulley size resolution Pulley Circumference Resolution 100mm 0 1mm 500mm 1mm 1 foot 0 01 In general there are three ways of using the...

Page 9: ...pulley alkaline battery and UNIDATA Micrologger fitted Config Model 6541B 0 Model 6541B 1x Model 6541B 2x Model 6541B 3x No pulley wheel 500mm circ pulley metric 1mm res 1 foot circ float pulley Imper...

Page 10: ...time and measurements are instantaneously available allowing the use of the aR0 commands The CRCed version of this command is also valid HSIO Interfaces The 6541B has Primary and secondary interfaces...

Page 11: ...same holes as the superseded 6509 Offset Pulley These attach to the instrument mounting bracket to guide the float line to hang correctly inside the float well They are not normally used as the added...

Page 12: ...instrument incorporates the UNIDATA 6541L Micrologger See Appendix A for details Water level is measured using the Micrologger s high speed serial IO channel The Micrologger has two analogue inputs an...

Page 13: ...logger Schemes are generally unique to a site or project The scheme instructs the logger What instruments are connected How and when to log the data How to scale the acquired data How to format the o...

Page 14: ...nnected to the correct terminal on the Field Termination Strip if you are using one or the correct pin in the INPUT SIGNALS connector if you are connecting directly to a STARLOGGER See your logger man...

Page 15: ...mbination of time and events say once each day and each time the level changes 10mm Time Based Logging The default method is time based logging and this is typically used for water level measurement T...

Page 16: ...e hour The sub interval allows you to average data over a portion of the log interval For example if you have selected a log interval of 1 hour and you enter a sub interval of 5 minutes the data you l...

Page 17: ...h log period Averaging data has the effect of smoothing out minor variations It is a useful way of eliminating spikes caused by waves or ripples Logging an average over a long period say one hour may...

Page 18: ...recovery of a period of data This will allow you to confirm satisfactory operation of the entire system and for the site operators to become familiar with the instruments and software 4 1 Controls and...

Page 19: ...evel Instrument STARLOGGER Prologger Wire Colour Logger Function Pin Term Pin Term Red 5 00V DC sync terminal 3 13 15 16 or 17 18 14 Green terminal 7 23 14 28 17 Blue DATA IN s0 terminal 5 21 11 32 11...

Page 20: ...ects to the logger s serial channel input S0 the second encoder s DATA IN blue wire connects to the first encoder s SERIAL LINK white wire S1 and so on The 5V DC red COMMON green and SERIAL CLOCK yell...

Page 21: ...DI 12 Signal Terminal 7 SDI 12 GND 4 5 2 Commands The SDI 12 commands below are useful for communicating with the 6541B Water Level Instrument Action Command to 6541B Response from 6541B Acknowledge A...

Page 22: ...4 to 20mA current loop output which is driven by a 16 bit converter on the main 6541B PCB The output loop compliance is from 0V Vloop supply 2 5V The zero level 4mA and span level 20mA points are prog...

Page 23: ...for I 4mA The span value is the level for I 20mA To save power the 6541B zero span values can be transposed providing a 20 4mA output PRESS HOLD UP DOWN BUTTONS TURN WLI ON Sw 8 HOLD BUTTONS FOR 5S S...

Page 24: ...mes a standalone logging instrument The HSIO interface wiring shall be configured as below 4 8 Connecting More Than One Instrument to a Logger Each serial channel on a STARLOGGER or PROLOGGER will sup...

Page 25: ...y should show the correct scheme details and the same value as displayed on the instrument LCD When you change the level displayed on the LCD by rotating the float pulley wheel the PC screen display s...

Page 26: ...through a cable gland in the base The Water Level Instrument should be protected from direct weather by a shelter It is not waterproof 5 2 Installing the Float System A float system consists of a flo...

Page 27: ...n the same level 1mm each time If it doesn t the float system is not moving freely The float line or counterweight may be rubbing on an obstruction or the instrument pulley may have on its shaft 6 Use...

Page 28: ...stable this is At many sites the UNIDATA Model 6256 STARFLOW system will be a better option for flow measurement In small channels it is common practice to construct a small weir flume or other measur...

Page 29: ...water level change The instrument is protected and kept dry clean and secure The cable to the data logger should be protected from damage 6 5 Measuring Rainfall Float instruments producing graphical c...

Page 30: ...structed from lightweight materials such as PVC pipe On larger rivers constructing new floatwells can be uneconomic and alternative instruments such as UNIDATA Pressure transducers should be considere...

Page 31: ...f the line on the opposite side of the pulley and run away The endless floatline is an alternative that eliminates the transfer of weight from one side of the float to the other and the errors so indu...

Page 32: ...l HSIO channels Data in Data out Sync Clock Current Loop Range 4 20 mA Span Zero User programmable DAC Resolution 16 bit Up to 8 instruments can be daisy chained Environmental Operating Temperature 10...

Page 33: ...Reprogrammable 8K EEPROM Inputs Outputs 1 x 16 bit Counter Channel 2 x Analog Channels Hi res 0 2 5V scaled 1 221mV bit A0 A1 2 x Digital Inputs Potential Free Log Start SENSE 1 1 x High Speed Serial...

Page 34: ...ear To Send 9 Ring Indicator Signal Communication Terminals Pin Label Description 1 UPS Output 2 GND Digital Power Ground 3 OUT0 Open Collector Control Output 4 INP0 Digital Input Log Start 5 GND Digi...

Page 35: ...form op code 132 UPS _of_ON_scans Pre scan_in_15 625ms_ lsb msb of On scans 0 UPS remains OFF 1 UPS ON next scan only 2 255 UPS ON next 2 255 scans Pre scan 0 UPS turns ON after I O measurement 1 UPS...

Page 36: ...n representation 8 bit 24 2 Counter channel C0 16 bit 32 1 Digital input values normally high Bit 3 Log Start Detect Log Start in memory Bit set not detected Bit 6 High speed serial Data 0 33 1 User P...

Page 37: ...nect the dual output PCB to the main PCB using the 14 pin header cable supplied and then mount the dual output PCB on the main PCB 5 Re connect the cable to the instrument see the illustrations for th...

Page 38: ...teel metric floatline with brass beads each 125mm Model 6541D I 1mm stainless steel imperial floatline with brass beads each 3 inches Model 6541E Previously model 6509E 0 4mm diameter lightweight and...

Page 39: ...and fittings Stainless Steel eye bolt for float line Ballasted to float at the centreline when used with a 160g counterweight Weight 1100g Model 6541F 115 This float is suitable for sites where a 6541...

Page 40: ...at the centreline when installed with a 160g counterweight Weight 430g Model 6541F 50 Previously part of 6509C This float is a long cylinder intended for use in small bores and float wells Smaller dia...

Page 41: ...mperial 6541P I 12 Use with 1mm cable with optional beads each 3 inches 100mm circumference Metric 6541P M100 Use with 0 4mm cable OEM Adaptor 6541U Mounting mechanism to suit pulleys with 0 5 12 7mm...

Page 42: ...t Systems All float systems are subject to a range of minor errors The errors involved in the recordings made by a properly designed float operated level recorder are generally too small to be of grea...

Page 43: ...s rising above a given reference starting point this error will make the level measure slightly high for a level falling below the reference point the error makes the level appear low The amount of er...

Page 44: ...Coefficient X Factor 1 2mm SS Beaded Cable 0 0000009 0 0009mm C metre 0 4mm Stainless Steel 0 0000009 0 0009mm C metre Supporting concrete 0 0000065 0 0065mm C metre Therefore the error expected from...

Page 45: ...6mm error occurs This example demonstrates the large errors that can result from the use of unsuitable components If the recommended 170mm float was used in the system described in the example the lin...

Page 46: ...influences do not affect the measurement you will need to use a floatwell stilling well 11 2 Floatwell Design A floatwell must be designed to suit the conditions at the measurement site Small sites m...

Page 47: ...t range If the floatwell is small a separate pipe can be used for the counterweight or offset guide pulleys can be used to re direct the floatline to a better location The instrument mount should be s...

Page 48: ...water enters the well and the silt settles in the still water If there are several entrances and exits through which water can flow lots of silt can be deposited In such cases there must be some way...

Page 49: ...rn improve the quality of the site data A major cause of data loss is interference by curious people or animals and vandalism All instruments should be inside locked cabinets and the floatwell design...

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