MAN-213 Vibrating Wire Precision Water Level
Contents
1. by reversing the sign of the K or G factor User Manual 2 04 Cable Jointing It is desirable to minimise cable joints but where they are unavoidable a special joint kit may be supplied The effectiveness of this joint largely depends on the care with which the jointing operation is carried out 2 04 1 Preparation of the Cable Thoroughly scrape all wax and dirt from each cable and for approximately 150mm Prepare the cable ends exactly as shown in Figure 5 Stagger the individual conductor connections 2 04 2 Conductor Connections Use the crimped connectors to join the conductors and use the electrical insulation tape to wrap the connectors Stretch the tape to half its original width and apply one layer half lapped over connector area only Figure 6 Do not warp the tape beyond the pencilled area 2 04 3 Fitting Mould Trim the ends of the mould with a sharp knife to suit the diameter of the cable Hold the mould halves in place centred over the splice Snap both halves together and fit the pouring spouts in the holes Ensure that both seams are completely snapped together Tape the ends of the mould body to form a seal 2 04 4 Filling with Resin Mix the resin thoroughly and maintaining the mould in a level position spouts uppermost pour the resin through one spout until both spouts are completely filled When the resin has solidified and cooled remove the spouts NOTE In cold weather below 15 the resin becomes very visc2. find out that 1 is equal to 0 01019 so we would derive the factor for KGF Cm by multiplying the K factor for kPa by 0 01019 Please see conversion factors in Section 10 Calculation using Linear units The following formula is used for readings in Linear units E G RO R1 User Manual 8 Where E is the resultant Engineering unit G the linear Gauge factor for the units of calibration from the calibration sheet RO is the Linear pase or zero reading Ri is the current Linear reading Again the Linear gauge factor for units other than the units of calibration would need to be calculated using the same principles as stated in the last paragraph of the Period unit section User Manual 9 Appendix A Example of Calibration Sheet Vibrating Wire PWLM BSI itmsoil Bell Lane Uckfield East Sussex t 44 0 1825 765044 e sales itmsoil com TN22 1QL United Kingdom f 44 0 1825 744398 w www itmsoil com ber stered fiel VIBRATING WIRE INSTRUMENT CALIBRATION CERTIFICATE Sensor Type Water Level Transducer Transducer Serial 21467 Range 0 300mm Weight Serial No 21466 Works Calibration Data Calibration Equipment Calibrated Weight Set Soil Equipment No 1160 Vibrating Wire Readout E031 Date 6 Jun 2006 Period Gauge Constant mm K 516 363722 Ambient Temp 24 C Period Gauge Constant gramms K 1968 1943 Calibrated By S Higgs F 1000 Gauge Constant mm Digi
3. tensioned wire and the force applying the tension is an approximate straight line relationship between the square of the measured frequency and the applied force Engineering units of measurement maybe derived from the frequency based units measured by vibrating wire readouts in 2 traditional ways From Period units and from Linear F2 1000 units Calculation using Period units The following formula is used for readings in Period units E K 10 7 P0 2 10 7 P1 2 Where E is the Pressure in resultant Engineering units K is the Period Gauge Factor for units of calibration from the calibration sheet PO is the Period base or zero reading Pi is the current Period reading This method of calculation is used by the Soil Instruments Vibrating Wire loggers models RO 1 VW 1 or 2 and with serial numbers starting VL TVL internal processors for calculating and displaying directly on the loggers LCD screen the required Engineering based units The loggers require Period base or zero reading units for entering into their channel tables to calculate and display correctly the required engineering units If an Engineering based unit is required other than the units of calibration then the correct K factor will have to be calculated using the standard relationship between Engineering units For example if the units of calculation required were in KGF Cm and the calibration units were kPa we can
4. 3 107 3 10942 1 0730 1 0589 10 960 35 960 804 78 1 15 562 2240 0 6 895 x 10 6 895 ilt 6805 1020 7043 02 3108 51 714 6 426 x 102 1 144 00 4 788 105 1 788 x 4883x 4788 1 555 x 10 4891x 605 x 107 0 3591 4 464 x 10 16 944 x 10 1 10 10 10 10 User Manual 11 Appendix C Troubleshooting If a failure of any vibrating wire transducer or the electrical cable is suspected the following steps can be followed The transducers themselves are sealed and cannot be opened for inspection The Troubleshooting Flowchart should also be followed if any instrument failures are suspected The steps below and the Troubleshooting Flowchart are applicable generally to any vibrating wire instrument STEP 1 Before any of the following steps are followed the portable data logger should be used to verify the stability of the reading and the audio signal from the portable logger should be heard An unstable wildly fluctuating reading from a transducer or an unsteady audio signal are both indications of possible problems with instruments or their related electrical cables If a portable data logger is giving faulty readings or audio signals from all transducers a faulty readout unit must be suspected Another readout unit should be used to check the readings from the transducers and Soil Instruments should be consulted about the faulty readout unit STEP 2 The resistance across the two conductors of the electrical cable should be checke
5. Preparation of Cable Joint User Manual 15 Pouring Spouts __ n yi _Mold Bodies T mE 20 IMPORTANT Cables and Connector Must be Centerd in Mold Figure 6 Cable Jointing Kit Wrapping Electrical Connectors amp Fitting Mould soil INSTRUMENTS Bell Lane Uckfield East Sussex t 44 0 1825 765044 e info itmsoil com TN22 1QL United Kingdom f 44 0 1825 744398 w www itmsoil com Soil Instruments Ltd Registered in England Number 07960087 Registered Office 5th Floor 24 Old Bond Street London W1S 4AW User Manual 16
6. ction 3 8 been TES 8 Appendix A Example of Calibration Sheet Vibrating Wire PWLM 10 Appendix B Conversion Factor 11 Appendix C Troubleshooting 4 eee iiie sees essen nenne nanenane ennn nnan nnan nasa ants 12 Figure 5 Preparation of Cable 15 Figure 6 Cable Jointing Kit Wrapping Electrical Connectors amp Fitting Mould 16 User Manual 2 Section 1 General Information 1 01 Description The Precision Water Level Meter PWLM consists of a cylindrical weight suspended from a vibrating wire strain gauge housed within a plastic stilling well The PWLM is designed to measure water levels in streams weirs and boreholes where accurate measurements of small water level changes are required 1 02 Operating Principle The weight connected to the strain gauge has a specific gravity that is slightly greater than that of water The strain gage works by measuring the load exerted by the weight s buoyant forces as the water level changes in relation to the fixed position of weight The change in load changes the wire s tension and resonant frequency The readout box supplies an electrical pulse to the coil magnet assembly which in effec
7. d This can be done using a multimeter device across the two exposed conductors if the cable has not been connected to a terminal cabinet or can be done just as easily across the two conductors if the instrument has been connected to such a terminal or datalogger The resistance across the two conductors should be approximately of the order of 1200 to 1800 The majority of this resistance will come from the transducer say approximately 130 Before proceeding to Steps 3 and 4 the continuity should be checked between conductors and earthing screen of the electrical cable If continuity exists a damaged cable is confirmed STEP 3 If the resistance across the two conductors is much higher than the values quoted in STEP 1 or is infinite a severed cable must be suspected STEP 4 If the resistance across the two conductors is much lower than the values quoted in STEP 1 say 800 or less it is likely that cable damage has occurred causing a short in the circuit STEP 5 If the resistance is within the values quoted in STEP 1 i e 1200 to 1800 AND no continuity exists between conductor and earth screen and on checking the reading from the transducer it proves to be still unstable or wildly fluctuating it must be assumed that the integrity of the circuit is good A faulty transducer could be suspected if neighbouring construction activities do not account for the anomaly Soil Instruments should be consulted If the point at w
8. hich the cable is damaged is found the cable can then be spliced in accordance with recommended procedures User Manual 12 User Manual R is very high TROUBLE SHOOTING FLOWCHART R less than 800 13 DECLARATION OF CONFORMITY WITH COUNCIL DIRECTIVE 73 23 EEC as Amended by 93 68 EEC Date of Issue 12 October 2006 DoC Soil CE L VDAMNV UB Directive T2 23 EEC Low Voltage Directive as amended by 93 68 Conforming Apparatus All Vibrating Wire Instruments Manufactured by Soil Instruments Ltd see pages 3 10 of Technical File Manufacturer Soil Instruments Ltd Responsible Person Chris Rasmussen Soil Instruments Ltd Bell Lane Uckfield East Sussex TN22 1QL Standards Referenced Annex of 1 3 26 2 0 2 0 3b amp 3 Directive Technical File Sail Instruments Ltd EU Low Voltage Directive 7 3 23 EEC as amended 93 68 EEC Technical Documentation Issue 1 October 2006 Vibrating Wire Instruments We hereby certify that the apparatus described above conforms with the protection requirements of 72 23 Low Voltage Directive as amended by 93 68 EEC on the approximation of the laws of the Member States relating to Low Voltage Equipment Signed 1 42 Signatory Chris Rasmussen Technical Director User Manual 14 5 00 5 00 0 Scrape Cut Sheath Back Cut Sheath Back Scrape Sheath Sheath 25 00 zi ie 25 00 Figure 5
9. nstant value Transit Screw NI Transit Screw User Manual 2 02 Cable Connection and Potting PWLM s are usually supplied with 5 metre of cable already connected to the transducer Additional cable lengths may be added on site using a cable jointing kit see section 2 04 2 03 Installation The stilling well should be installed vertically in a position where there is little water turbulence The vertical position should be such that the weight of the PWLM will be in the desired position relative to the water level After installation of the stilling well connect the PWLM to the cap of the stilling well and lower the assembly into the stilling well It is important that the PWLM is centred within the stilling well and that the weight is not touching the side of the stilling well as this will influence the sensor output After installation the seal screw should be removed from the moisture trap The trap should be positioned in a dry environment away from the stream or weir The installation zero reading should now be taken and recorded for later use in data reduction It is advisable to test the PWLM by raising the cap a few centimetres and recording the change in reading and then calculating the change in engineering units This will ensure that you are aware of the direction of change of the engineering units raising the cap simulates a drop in water level You can reverse the indicated direction of change
10. ous It is therefore advisable to keep the resin in a warm place prior to mixing Mix the compound until its temperature starts to rise this decreases the viscosity User Manual 6 Section 3 Termination of Cables The cables are normally terminated in a 5 channel terminal box or 12 and 24 channel terminal units The cables enter through waterproof glands The terminal box has a cover secured by four screws whereas the terminal units have a hinged lid The cables are terminated as follows Unscrew the cover or open the lid as appropriate Unscrew the four fixing screws holding the terminal panel and carefully remove it without straining the connecting leads Prepare the cables by stripping and cutting back 20cm approximately of the outer insulation and armour Remove the rubber packing and strip back 5cm of the conductor insulation Slacken the entry glands and insert the cables Make connections to the contact block details of colour coding supplied with each instrument Retighten the glands to grip the cables Replace the terminal panel and secure Connect the readout to each instrument in turn to check connections User Manual Section 4 Vibrating Wire Precision Water Level Meter Data Reduction Procedures 4 01 The Calibration Certificate The end of this section shows example of the Calibration Certificate as supplied with each PWLM 4 02 Data Reduction The mathematical relationship between the frequency of vibration of a
11. scil INSTRUMENTS Vibrating Wire Precision Water Level Meter User Manual oo Man213 1 0 2 07 08 2014 Day Chris Rasmussen Chris Rasmussen Manual No Revision Date Originator Checked Authorised for Issue User Manual Contents Section 1 General Information 3 1 01 IBI Te 55 55 15 DEAE REDONDA DC RC IHR ETE 3 1 02 Operating Pririciple c Ie Ete ee 3 1 03 s HER 3 Section 2 Installation of Precision Water Level 4 2 01 Test Prior to Installation cor ies c EUREN a A rM UE CUIR 4 2 02 Gable Connection and Potting en exe ere v pa xe 5 2 03 TASCA ACI OM es eT 5 2 04 Cable Jointing 6 2 04 1 Preparation of the Cable aie ea eae RETRO RE 6 2 04 2 Conductor Connections ers ere rera ete ded dea esa dees 6 2 04 3 Fitting Mould e RENA 6 2 04 4 Filling with RESIN ER RR SRI 6 Section 3 Termination of Cables eesiieeeieee eiie essen 7 Section 4 Vibrating Wire Precision Water Level Meter Data Reduction Procedures 8 4 01 The Calibration Certificate E E E AEE 8 4 02 Deitea Red
12. t G 0 0516364 Weight Ave Diameler mm 69 66 F 1000 Gauge Constant gramms Digit G 0 1968194 Weight Volume Factor V 3 8116 WATER LEVEL TRANSDUCER CALIBRATION The instrument detailed hereon has as applicable been tested and calibrated in accordance with procedures which are part of our 509001 2008 Quality Management System and unless otherwise indicated performs within 0 0596 as specified Thus the in Certified By Line Manager User Manual 10 Appendix B Conversion Factor Chart Pressure Stress amp Modulus of Elasticity 0 1013 101 33 9 788 x 10 9 7885 2 983 x 10 12 9835 1 333 x 10 0 1333 0 100 100 0 1 0197 1 0 9869 10 215 33 515 1 0332 9 983 x 10 3 043 x 2 984 x 107 102 1 3595 1 333 103 10 1 0132 9 789 x 107 10 351 33 959 2 945 x 107 0 3048 1 750 06 760 02 22 377 1 1000 10 197 10 000 9 869 102 2 335 2 7500 6 9 320 145 04 20886 0 001 1 Ti x 0 0100 9 87 x10 0 1022 0 3352 7 5006 0 0093 0 14504 20 886 9 807 102 9807 1 0 9807 0 9678 10 017 32 866 735 56 0 9139 14 223 2048 1 14 504 14 696 0 9320 0 9444 1 9 661 x 10 1 3 2808 73 424 9 124 x 10 1 4198 204 45 2 781 x 107 0 43275 1 315 x 10 i X 4 469 x 10 1 1 243 x 10 1 934 x 10 2 7846 2088 6 2116 2 62 316 0 107
13. t plucks the wire and causes it to vibrate at its resonant frequency The coil magnet assembly then acts as a pickup as the oscillations of the wire through the magnetic field induce an alternating current in the coil which is detected by the readout The readout converts the sinusoidal alternating voltage to a square wave from which may easily be timed using a frequency oscillator In this way the period of oscillation may accurately be measured The relationship between a change in the period of oscillation and the strain of the wire is non linear so to facilitate the reading procedure the readout converts the period of oscillation to frequency squared which has a linear relationship to strain 1 03 Performance The PWLM has a very good long term stability but are sensitive to temperature and an allowance for temperature variations may be necessary when interpolating the results The PWLM s can accommodate a thermistor to monitor temperature if such variations are anticipated User Manual Section 2 Installation of Precision Water Level Meter 2 01 Test Prior to Installation Before installation the PWLM should be subjected to an operational test with the portable readout connected as follows Suspend the PWLM and gently attached the weight loosen the two transit screws that secure the weight hanging hook The hook should hang freely and not be in contact with the body or the transit screws Take a zero reading which should be of a co
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