MODEL TES-GS-30V VIBRATING WIRE SETTLEMENT MEASUREMENT SYSTEM

Transcription

1 USERS MANUAL MODEL TES-GS-30V VIBRATING WIRE SETTLEMENT MEASUREMENT SYSTEM Doc. # WI Rev. 01 Printed March, 2008

2 1 Introduction The TES-GS-30V settlement cell is designed for monitoring soil settlement by using a vibrating wire pressure sensor. It finds major application in measuring settlement in embankments and embankment foundations. It is used to measure soil settlement due to de-watering and subsidence due to tunnelling & mining operations. Settlement in marine fills & consolidation under heavy storage tanks is also monitored. The system consists of a vibrating wire pressure sensor of specified range, a reservoir and two fluidfilled tubes connecting the reservoir to the sensor. The settlement cell is normally installed in a soil fill. One end each of the two tubes is connected to the cell and the other end to the reservoir. As the settlement cell settles with the surrounding ground, the height of fluid column increases and the sensor measures the higher pressure. Settlement is read on the TES-DI-51V vibrating wire indicator by noting the difference in pressure readings in terms of meter. The sensor and the tubes are completely buried in soil. They do not therefore interfere with any construction activity and are less likely to be damaged. The readings also are taken remotely at a place where the reservoir is located; again avoiding interruption of construction activity. A thermistor is provided in the pressure sensor for measurement of temperature. Each transducer is individually calibrated for change in zero reading due to temperature changes. The correlating data due to temperature induced frequency changes is provided in the test report. As density of the fluid changes with temperature, necessary corrections may be made if required. Generally no correction is required as the sensor and nylon tubes are embedded in soil. 1.1 Specifications of sensor Sensor capacity Temperature limit Integral thermistor Enclosure Cable Read out unit 7, 15, 30, 50, 70 m Operational -20 to 70 o C; compensated 0 to 55 o C YSI or equivalent Stainless steel CS-0501 four core vented cable for 7, 15 m sensors CS-0702 four core cable for higher capacity sensors TES-DI-51V portable read-out unit/data logger 1.2 Instrument and its accessories Sensor assembly with liquid filled twin tube and connected cable Settlement plate with fasteners Enclosure Fluid reservoir Desiccant chamber Desiccant De-aerated liquid 1.3 Installation tool kit and consumables Digital multi meter Screw driver set Acetone (commercial) Adjustable spanner Hacksaw with 150 mm blade Surgical blade with holder Wire stripper Page 1-1

3 1.4 Conventions used in this manual WARNING! Warning messages calls attention to a procedure or practice, that if not properly followed could possibly cause personal injury. CAUTION: Caution messages calls attention to a procedure or practice, that if not properly followed may result in loss of data or damage to equipment. Note contains important information and is set off from regular text to draw the users attention. 1.5 How to use this manual This users manual covers description of the vibrating wire settlement cell with its accessories, the installation procedure, maintenance of the sensor, method of taking observations and recording the data from the sensor. This manual is intended to provide you with sufficient information for making optimum use of vibrating wire settlement cell in your applications. The installation personnel must have a background of good installation practices and knowledge of the fundamentals of geotechnics. Novices may find it very difficult to carry on the installation work. Intricacies involved in installation are such that even if a single essential but apparently minor requirement is ignored or overlooked, the most reliable of instruments will be rendered useless. A lot of effort has been made in preparing this instruction manual. However the best of instruction manuals cannot provide for each and every condition in the field that may affect the performance of the sensor. Also, blindly following the instruction manual will not guarantee success. Sometimes, depending upon field conditions, the installation personnel will have to consciously depart from the written text and use their knowledge and common sense to find the solution to a particular problem. To make this manual more useful we invite your valuable comments and suggestions regarding any additions or enhancements. We also request you to please let us know of any errors that you may find while going through this manual. The manual is divided into a number of sections. Each section contains a specific type of information. The list given below tells you where to look for in this manual if you need some specific information. For understanding principle of vibrating wire settlement cell: See 2.1 Operating principle. For general description: See 2.2 General description. For test certificate: See 2.4 Sample test certificate. For installation of vibrating wire settlement cell: See 3 Installation. For evaluating thermistor data: See 4 Thermistor - temperature resistance correlation. Page 1-2

4 2 2.1 Operating principle The settlement cell consists of a vibrating wire pressure sensor of specified range, a reservoir and two fluid-filled tubes connecting the reservoir to the sensor. The pressure sensor is normally installed in a soil fill. One end each of the two tubes is connected to the sensor and the other end to the reservoir. As the sensor settles with the surrounding ground, the height of fluid column increases and the sensor measures the higher pressure. Settlement is read on the TES-DI-51V vibrating wire indicator by noting the difference in pressure readings in terms of meter. The vibrating wire pressure sensor basically consists of a magnetic, high tensile strength stretched wire, one end of which is anchored and the other end fixed to a diaphragm that deflects in some proportion to the applied pressure. Any change in pressure, deflects the diaphragm proportionally and this in turn affects the tension in the stretched wire. Thus any change in pressure, directly affects the tension in the wire. The wire is plucked by a coil magnet. Proportionate to the tension in the wire, it resonates at a frequency f, which can be determined as follows: f = [σg/ρ] 1/2 / 2l Hz σ = tension of wire in kg/cm 2 g = 980 cm/sec 2 ρ = density of wire in kg/cm 3 l = length of wire in cm Figure 2.1 Enclosure with reservoir, desiccant chamber and terminal board The resonant frequency, with which the wire vibrates, induces an alternating current in the coil magnet. This is read by the read out unit. Summarizing, any variation in settlement increases the water pressure on the sensor causing the diaphragm to deflect. This changes the tension in the wire thus affecting the frequency of vibration. The pressure is proportional to the square of the frequency and the read out unit is able to display this directly in engineering units. 2.2 General description VW Settlement cell The settlement cell basically consists of (refer to figure 2.2): Pressure sensor of capacity 7, 15, 30, 50, 70 m with a thermistor for measurement of temperature and gas discharge tubes for protection against lightning damage. Base plate (paper phenolic board 300 mm x 300 mm x 5 mm). Mounting bracket (angle) for fixing pressure sensor to base plate. Page 2-1

5 Resolution of system depends upon range of the settlement cell. Accuracy and repeatability depend on proper installation, maintenance of de-aired fluid and application of temperature corrections. Polynomial linearity correction for pressure sensor is provided in the test certificate Tubing Figure 2.2 Settlement cell layout The TRITECH settlement cell is connected to the reservoir by a polyethylene sheathed twin nylon tubing. Use of two fluid-filled tubes permits periodic flushing of tubing for removing any accumulation of air bubbles. Normally the fluid used is a de-aired antifreeze/water mixture to prevent freezing and resist growth of algae Vented polyurethane sheathed signal cable The shielded cable has a vent tube running from inside the sensor to the outside atmosphere ensuring that sensor reading is unaffected by any change in barometric pressure. The reservoir end of the vent tube terminates into a desiccant chamber in the enclosure thus preventing any moisture from migrating into the vent tube Enclosure Item Description Qty. 1. Base plate (paper phenolic board) 1 2. Sensor mounting bracket 1 3 VW sensor assembly 1 4 Allen head screw M16x12 with nut 2 5 Allen head screw M6x8 2 6 Cable 4-core vented As reqd. 7 Instant fitting 2 8 Twin tube As reqd. 9 Cable tie 150 mm long 1 A wall mounted 300 mm W x 400 mm H x 210 mm D enclosure houses the reservoir, desiccant chamber and terminal board. Refer to figure 2.1 and 2.3. The standard enclosure has provision for connecting one settlement cell to the reservoir. However, if specifically requested the enclosure can be factory provided for connecting two settlement cells to the reservoir. Refer to figure 2.4. In case more than two settlement cells are to be connected to the reservoir, a separate junction box for the cable connections and a separate manifold for the twin tubing is available from the factory for connecting to Page 2-2

6 Users manual the standard enclosure. Refer to figure 2.5 and 2.6 for switch box and a manifold system suitable for seven settlement cells. These are specifically factory made depending upon the number of settlement cells to be connected to the standard enclosure. Figure 2.7 gives details of how the tubing and wiring connections are made between the sensors, manifold, junction box and the reservoir/desiccant chamber in the wall mounted enclosure. Moisture trap Enclosure (300x400x210 mm) Reservoir Air vent tube Liquid Shut-off valve Nylon twin tubes Liquid head Vented cable Settlement plate V/W settlement cell Figure 2.3 Schematic of settlement system Figure 2.5 switch box Figure 2.4 Enclosure suitable for two settlement cells Figure 2.6 Manifold system for upto seven settlement cells Page 2-3

7 Fluid reservior Reservior system Desiccant Desiccant chamber Output cable to DAS Switched output Selector switch Screwed terminals COMM Vent tube Manifold system Flushing valve Switching system Cables from sensor Twin tubes from sensor Figure 2.7 Typical observation room layout suitable for seven sensors Page 2-4

8 Users manual De-aired fluid A mixture containing 50% ethylene glycol and 50% de-aired water is used for maintaining the fluid level in the reservoir and filling the nylon tubes. The mixture has a relative density of 1.06 at 4 C. Ethylene glycol is a good wetting agent and also an antifreeze. A foot pump is required to pump de-aired fluid through the nylon tubes. While using foot pump to circulate the fluid, always monitor the sensor pressure ensuring that it does not exceed the capacity of the settlement cell. If air bubbles are present in the tubes, they can cause errors because air is lighter than the fluid fill. Any suitable pump may be used instead of a foot pump. 2.3 Taking readings with the model TES-DI-51V vibrating wire indicator Model TES-DI-51V vibrating wire indicator is a microprocessor based readout unit for use with TRITECH s range of vibrating wire sensors. It can display the measured frequency in terms of time period, frequency, frequency squared or value of measured parameter directly in proper engineering units. It can store calibration coefficients of up to 500 vibrating wire transducers. The indicator has an internal non-volatile memory with sufficient capacity to store about 4,500 readings from any of the 500 programmed transducers in any combination. 4,500 sets of readings can be stored either from any one transducer or 9 sets stored from all 500 transducers. Each reading is stamped with date and time of taking measurement. Calibration coefficients are given in the individual Test Certificate provided with each transducer. Refer to model TES-DI-51V instruction manual WI for entering the transducer calibration coefficients. The gage factor given in the test certificate and the zero reading in frequency 2 (digits) at the time of installation are used for setting up the transducer coefficients in the readout unit. The Test certificate also gives factory zero reading in frequency 2 for use with transducers provided with polynomial linearity correction. For polynomial linearity correction, pressure is calculated by following equation: P = A(R1)² + B(R1)² + C m where P = pressure in engineering unit R1 = current reading in digits during observation A, B, C = polynomial constants The polynomial constants are stored in model TES-DI-51V memory to give linearity corrected data of the parameter in engineering units. For more details refer to 6.2 of this manual and instruction manual WI of model TES-DI-51V. For transducers with a built-in interchangeable thermistor, the model TES-DI-51V can also display and record the temperature of the transducer directly in degree Centigrade. Any TRITECH vibrating wire sensor with the exception of the temperature sensor has a thermistor incorporated in it for temperature measurement, unless not required specifically by the customer. The stored readings can either be uploaded to a host computer using a serial interface or can be printed out on any text printer equipped with a RS-232C serial communications interface. The set-up information (calibration coefficients) for all the channels can also be printed out for verification. The readout indicator is powered by an internal 6 V rechargeable sealed maintenance free battery. A fully charged new battery provides nearly 60 hours of operation on a single charge. A separate battery charger is provided with the TES-DI-51V indicator to charge the internal battery from 230 V AC mains. The TES-DI- 51V indicator is housed in a splash proof resin moulded enclosure with weatherproof connectors for making connections to the vibrating wire transducer and the battery charger. Page 2-5

9 2.4 Sample test certificate TEST CERTIFICATE DWT Traceable to standard no. : G RED 090 TC Customer : P.O.No. : Instrument : Date: Model : TES-GS-30V Temperature:20 C Serial number : XYZ Atm. pressure: m wc Capacity : 7 m wc (6.57 m AFL) Twin tube length : -----m (Tubing filled with 1:1 mix of water and anti-freeze liquid (AFL) specific gravity 1.065) Input Corresponding Observed data Average End Point Poly Non Conformance pressure AFL column Up1 Down Up2 Fit Fit (% FS) (m wc) (m AFL) (Digit) (Digit) (Digit) (Digit) (m AFL) (m AFL) Non linearity (% FS): 0.46 Accuracy( % FS): 0.13 Digit : f ² X 10E-3 Gage factor (G) : 1.466E-03 m /digit (Use gage factor with minus sign with our read out unit Model : TES-DI-51V) Thermal factor (K) : m / C Polynomial constants : A = E-09 B = E-03 C = E+01 Pressure "P" is calculated with the following equation: Linear, : P(m) =G(R0-R1)+K(T1-T0)-E Polynomial, : P(m) = A(R1)² + B(R1) + C+K(T1-T0)-E R1 = current reading & R0 is initial reading in digit. T0 = Initial temperature ( C) and T1 is current temperature ( C) E = Change in reservoir level in m Pin configuration/wiring code: Red & blue: Signal Green & yellow: Thermistor Checked by Tested by Page 2-6

10 3 Installation The TRITECH model TES-GS-30V vibrating wire settlement system is suitable for measurement of settlement or heave in an embankment of a dam, embankment foundation or in fills. It can also be used to monitor settlement or heave of a structure by directly attaching the settlement cell along with cables to it. The VW settlement cell comprises of a precision vibrating wire pressure sensor connected to a reservoir through a twin nylon tube. The tube and reservoir are filled with de-aerated anti-freeze fluid. The VW settlement measures the pressure of fluid column acting on the diaphragm of pressure sensor. The reservoir is installed above the pressure sensor (not more than the range of sensor). Its location must always be at an elevation higher then the settlement cell and also above any part of the fluid-filled twin tubing. The pressure sensor fixed on a settlement plate and placed at the required location moves along with adjacent soil or structure helping to measure any settlement or heave. The settlement cell along with twin tubing is generally supplied pre-filled with de-aired anti freeze fluid. To protect settlement cell from being subjected to over range by pressure and temperature variation, an extra length of smaller diameter tubing is connected to the outer ends of twin tubing to allow system to breathe. 3.1 Check sensor Check working of the sensor as follows: The coil resistance measured by a digital multimeter between the red and black pins, should lie between Ohm. Determine resistance at room temperature from thermistor temperature resistance chart in 4. This resistance should be approximately equal to that between pins marked green and white. For example, if room temperature were 25 o C, the resistance would be 3,000 Ohm. The resistance between any lead and the protective armour should be > 500 M Ohm. Connect sensor to TRITECH model TES-DI-51V portable readout unit and switch it on. The display will show something like: Freq: Hz where the actual figure will vary depending on the transducer connected to the indicator. This initial reading on the portable readout unit should be stable. Check whether sensor is responding to changes in pressure. A crude but simple and effective method of checking whether sensor is responding to changes in pressure is as follows: Place the settlement cell on the floor. Raise the free end of the fluid filled twin tubing by around a meter. Verify that frequency reading on indicator decreases. This change in reading ensures that deformation produced by raising the twin tubing is transmitted to vibrating wire sensing element. 3.2 Installation of Settlement cell, tubing and cable Attach pressure cell to base plate and secure cable with cable tie as shown in figure In case a structure is to be monitored, attach settlement cell directly to it by means of expandable/groutable fasteners and bolts. When mounting on structures, cable and tubing should be adequately supported along its length to prevent stretching and waviness. Settlement cell, cable and tubing must be protected from direct sunlight and insulated from rapid temperature fluctuations by encasing them in thermocole, styrofoam or urethane foam, etc. Page 3-1

11 3.2.3 In case an embankment or a fill is to be monitored, locate exact position where settlement cell has to be installed by surveying. Excavate a smooth flat-bottomed block of around 300 to 600 mm deep. Place settlement cell at bottom and note elevation by level surveying. Use hand shovel to cover settlement cell with fine sieved material similar to the fill. Tamp material around cell filling back the trench. Compaction may be done with a light duty pneumatic or petrol backfill tamper. Check functioning of sensor after tamping Make a gradually sloped 300 to 600 mm deep trench from this block to point where reservoir is to be installed. A gradual slope helps in avoiding formation of air pockets in the tubing. Properly clean the trench, ensure that its bottom is smooth, not wavy and any sharp material that can damage the cable or the tubing is removed Lay down tubing along with cable in sloped trench from sensor to location of the reservoir. Care should be taken to avoid kinks or sudden bends in the tubing and cable. Slake the tubing in the trench to allow for ground movement. Lay cable and tube side by side without touching it and crossing each other. At no place tubing should be higher than the reservoir level Use hand shovel to cover cable and tubing with fine sieved material similar to the fill. Large angular and sharp rocks should not be allowed to come in contact with the cable and tubing. Tamp material around cable and tubing, filling back the trench. Compaction may be done with a light duty pneumatic or petrol backfill tamper. Check functioning of sensor after back filling and tamping of trench is completed.. To prevent migration of water along the trench, bentonite plugs can be constructed at intervals. To prevent migration of water along the trench, bentonite plugs can be constructed at intervals. In case of an earth dam, before packing the trench with back fill, a plug approximately 100 mm thick, made of a mixture of 5% bentonite (by volume) exhibiting a free swell factor of approximately 600%, and 95% sand should be placed in the trench at intervals of approximately 10 m. CAUTION: The cable and tubing should be suitably protected from damage due to construction activity, weather changes and vandalism. Tubing must be protected from stretching as a result of differential compaction of surrounding material. Cable and twin tubing should be laid in the trench by rolling the cable reel on its periphery. Under no circumstances should the tubing be unwound from any one side of the reel. This can happen, for example, when the tubing is kept on its side and is taken out without rolling the cable reel. Do not move any construction equipment over installation till a further 1 m is back filled. Contact of any sharp or angular objects with the nylon tubing must be avoided 3.3 Installation of reservoir The reservoir is normally installed on stable ground at an elevation higher than the sensor and any part of fluid filled connecting tubing, depending upon the capacity of sensor. Elevation of reservoir should be surveyed and recorded at the time of initial installation for verification at any subsequent date. Any settlement or heave in the settlement cell can be measured by measuring reading of pressure sensor on TES-DI-51V VW Indicator. The Enclosure should be firmly grouted in the ground or on a concrete pad or fixed on a wall in a stable room at the location. The reservoir should never be located where it is exposed to direct sunlight. Page 3-2

12 Users manual Settlement is measured with respect to the reservoir. The reservoir may itself be subjected to lateral and vertical shift. A survey marker pin should be provided at a suitable location on the place, preferably on the rooftop. The survey pin position (northing, easting and elevation) should be determined just after installation and from then on checked periodically. This will enable the settlement measurement to be corrected to get absolute values. The reservoir should be installed at a convenient height near eye-level, stable enough to be un-disturbed by movement of heavy vehicles or any other ground movement. In no case should elevation of reservoir be higher than elevation of sensor and the difference should never exceed range of settlement sensor Remove top cover of fluid reservoir and fill the reservoir with de-aired anti-freeze fluid until it is half full Connect tubings from sensor to the ports (when more than one sensor is connected to a single reservoir, use manifold and switch box figure 2.7). Do not allow air to be trapped inside tubing during connection Connect vent tube to the desiccant chamber (moisture trap). Put desiccant into it. Check that the connecting tubing between desiccant chamber and fluid reservoir is not blocked A few drops of light oil may be added through the top of reservoir. It will prevent evaporation of liquid from surface of fluid reservoir Connect sensor cable to the terminal panel, if one exists: Black and Red wires are connected to the gage position; Green and White wires are connected to the thermistor (temperature) position. 3.4 Taking initial reading Connect sensor cable RED BLACK for coil and GREEN-WHITE for thermistor Note down initial reading with the help of TES-DI-51V VW Indicator. This reading (IR) will be taken as reference reading Initial reading forms the reference with which all subsequent readings are compared. It should therefore be taken very carefully. Readings should be taken only when fluid filled tubing is at constant temperature. In fills and embankments it is usually so as the tubing is buried. However, when monitoring structures, it may not be so. No readings should be taken when tubing or sensor is exposed to sunlight directly and/ or any air bubble is detected in the tubes. Also take care that there are no air bubbles in the tubing. Presence of air bubbles will give an erroneous reading. If air bubbles are detected or suspected, flush the tubing with fresh de-aerated fluid. You may have to repeat the process till the reading becomes stable Note down fluid level in reservoir with a steel scale and put a mark on the reservoir. This will serve as a quick check for readings to be taken subsequently. Top up fluid in case the level in reservoir has gone down. Level change in reservoir may be due to change in temperature or pressure or due to leakage Record the ambient temperature Determine northing, easting and elevation of survey pin on the terminal structure. Page 3-3

13 No readings should be taken when any air bubble is detected in the tubes. In case air bubble is seen flush the system again and take readings. Always record temperature, as reservoir level may vary due to variation in temperature. 3.4 Flushing of twin tubes Close all valves except V2, V3 and respective inlet and outlet valve Vix and Vox of the particular sensor under flushing. Pump in de-aerated fluid through valve V3 till bubble free fluid comes out of V2 (refer to figure 3.1) Close valve Vix. & again pump in de-aerated fluid through valve V3 till bubble free fluid comes out of V2 (refer to figure 3.2) Open valve V1 slightly so that any air trapped comes out of reservoir. Do not allow water to fill the fluid reservoir completely (refer to figure 3.3) Close valve V1, V2 and V3. The schedule of installation of sensor for VW cell settlement system shall be different for each sensor installed at different locations and elevations. The flushing operation for twin tubes may be carried out after installation of sensors and prior to recording the initial reading. Fluid reservior V1 V2 Drain Vo V3 Inlet Vi Valve open V W cell Valve close Figure 3.1 (VWS switching step-1) Fluid reservior Repeat the above flushing process for all the sensors connected to reservoir system through manifold system and switching system Open valve V1, Vix and Vox for observation. V1 V2 Drain 3.5 Calculation of settlement The settlement of sensor can be calculated by: H=(D 0 -D 1 ) XG F - E Vo Vi V3 Inlet Where H is the settlement in mm D 0 is the initial reading of sensor in digits D 1 is the subsequent reading of sensor in digits V W cell Figure 3.2 (VWS switching step-2) G F is the gage factor supplied with the sensor in m/digit Page 3-4

14 Users manual E is the change in reservoir reading in m Fluid reservior (If fluid level falls, E is negative. If fluid level rises, E is positive) TES-DI-51V VW Indicator can directly read settlement reading [(D 0 -D 1 ) x G F ] by feeding Initial reading and gage factors in the set up. V1 V2 Drain 3.6 General precautions in routing of cable Careful and skilled routing of cable is required as cable is the life of sensor. The following points are particularly emphasized: Vo Vi V3 Inlet Cables & tubes should not get damaged during routing or further construction activities. V W cell Cable & tube must be protected from stretching as a result of differential compaction of surrounding material. Figure 3.3 (VWS switching step 3) All cables should be properly identified by tagging particularly at the point from where they come out of the borehole or ground. The tags should be of a non-corrosive material like stainless steel or plastics. The cables & tubes should be suitably protected from damage due to construction activity, weather changes and vandalism. Precaution must be taken that cables are properly tagged, onward from point where the sensors are installed. With the best possible precautions, mistakes may still occur. Tags may get lost due to cable getting accidentally cut. TRITECH uses the convention that looking from the end of the trench towards the sensor, the cable from the most distant sensor is always at the left hand side and the offset trenches are to the right of the cable trench. In that order, the cable from the closest sensor is at the extreme right. In dam fill it is convenient to install sensor and cable in a trench. By doing so, adequate degrees of compaction of the backfill can be more easily obtained without damage to the sensor or the cable trench. As the sensors and cables are covered and compacted, repeated readings should be taken to ensure that the sensors continue to function properly. 3.7 Connection to DAS The VW cell settlement system maybe connected to a data acquisition system for long term monitoring of data. However, it must be noted that for the settlement reading to be reliable, it will be necessary to monitor the fluid level in the reservoir regularly. 3.8 Trouble shooting The settlement cell is generally installed in soil fills. Once installed, the settlement cell is usually inaccessible and remedial action is limited. Maintenance and trouble shooting is consequently confined to periodic checks of cable connection and functioning of the read-out unit. Refer to the Page 3-5

15 following list of problems and possible solutions should problems arise. For any additional help, consult the factory Symptom: settlement cell reading unstable Check the insulation resistance. The resistance between any lead and the protective armour should be > 500 m Ohm. If not, cut a meter or so from the end of cable and check again. Does the read-out work with another settlement cell? If not, the read-out may have a low battery or be malfunctioning. Consult the manual of the readout unit for charging or trouble shooting instructions. Use another read-out unit to take the reading. Check if there is a source of electrical noise nearby? General sources of electrical noise are motors, generators, transformers, arc welders and antennas. If so the problem could be reduced by shielding from the electrical noise Symptom: settlement cell fails to read The cable may be cut or crushed? If the resistance reads infinite or a very high value, a cut in the cable is suspected. If the resistance reads very low (<100 Ohm), a short in the cable is likely. Does the read-out work with another settlement cell? If not, the read-out may have a low battery or be malfunctioning. Consult the manual of the readout unit for charging or trouble shooting instructions. Use another read-out unit to take the reading. Page 3-6

16 4 Thermistor - temperature resistance correlation Thermistor type: Dale 1C3001-B3 Temperature resistance equation T = 1/[A + B(LnR) + C(LnR) 3 ] o C T = temperature in o C LnR = Natural log of thermistor resistance A = x 10-3 B = x 10-4 C = x 10-7 Ohm Temp. o C Ohm Temp. o C Ohm Temp. o C 201.1k K K K K K K K K k K K K K K K K K K K K K K K K K K K K K K K K K k K K K K K K K K K K K K K K K Page 4-1

17 4.1 Measurement of temperature Thermistor for temperature measurement is integral with all settlement cell. The thermistor gives a varying resistance output related to the temperature (see 4). The thermistor is connected between the green and white leads. The resistance can be measured with an Ohmmeter. The cable resistance may be subtracted from the Ohmmeter reading to get the correct thermistor resistance. However the effect is small and is usually ignored. The TRITECH model TES-DI-51V read-out unit gives the temperature from the thermistor reading directly in o C. 4.2 Temperature correction Each vibrating wire sensor is individually calibrated for temperature zero drift In case a level - temperature variation correlation is required, the correction for the temperature effect on the sensor can be made by making use of the temperature zero shift factor (K) provided in the test certificate (see 3.10) and substituting it in the following equation: P c o r r e c t i o n = (current temperature - initial temperature) x K The temperature correction value is added to the stress value read from the TES-DI-51V read-out. Page 4-2

18 5 WARRANTY The Company warrants its products against defective workmanship or material for a period of 12 months from date of receipt or 13 months from date of dispatch from the factory, whichever is earlier. The warranty is however void in case the product shows evidence of being tampered with or shows evidence of damage due to excessive heat, moisture, corrosion, vibration or improper use, application, specifications or other operating conditions not in control of TRITECH. The warranty is limited to free repair/replacement of the product/parts with manufacturing defects only and does not cover products/parts worn out due to normal wear and tear or damaged due to mishandling or improper installation. This includes fuses and batteries If any of the products does not function or functions improperly, it should be returned freight prepaid to the factory for our evaluation. In case it is found defective, it will be replaced/repaired free of cost. A range of technical/scientific instruments are manufactured by TRITECH, the improper use of which is potentially dangerous. Only qualified personnel should install or use the instruments. Installation personnel must have a background of good installation practices as intricacies involved in installation are such that even if a single essential but apparently minor requirement is ignored or overlooked, the most reliable of instruments will be rendered useless. The warranty is limited to as stated herein. TRITECH is not responsible for any consequential damages experienced by the user. There are no other warranties, expressed or implied, including but not limited to the implied warranties of merchantability and of fitness for a particular purpose. TRITECH is not responsible for any direct, indirect, incidental, special or consequential damage or loss caused to other equipment or people that the purchaser may experience as a result of installation or use of the product. The buyer s sole remedy for any breach of this agreement or any warranty by TRITECH shall not exceed the purchase price paid by the purchaser to TRITECH. Under no circumstances will TRITECH reimburse the claimant for loss incurred in removing and/or reinstalling equipment. A lot of effort has been made and precaution for accuracy taken in preparing instruction manuals and software. However best of instruction manuals and software cannot provide for each and every condition in field that may affect performance of the product. TRITECH neither assumes responsibility for any omissions or errors that may appear nor assumes liability for any damage or loss that results from use of TRITECH products in accordance with the information contained in the manuals or software. Products described in TRITECH s catalogs are subject to modification and improvement as dictated by subsequent developments. TRITECH reserves the right to modify, change or improve products, to discontinue them or to add new ones without notice. Page 5-1

19 TABLE OF CONTENTS 1 INTRODUCTION Specifications of sensor Instrument and its accessories Installation tool kit and consumables Conventions used in this manual How to use this manual VIBRATING WIRE SETTLEMENT CELL Operating principle General description VW Settlement cell Tubing Vented polyurethane sheathed signal cable Enclosure De-aired fluid Taking readings with the model TES-DI-51V vibrating wire indicator Sample test certificate INSTALLATION Check sensor Installation of Settlement cell, tubing and cable Installation of reservoir Taking initial reading Flushing of twin tubes Calculation of settlement General precautions in routing of cable Connection to DAS Trouble shooting Symptom: settlement cell reading unstable Symptom: settlement cell fails to read THERMISTOR - TEMPERATURE RESISTANCE CORRELATION Measurement of temperature Temperature correction WARRANTY 5-1 i