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Geokon 4200 Series, Instruction Manual

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Geokon 4200 Series Instruction Manual Download Page 5

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TABLE OF CONTENTS

1. INTRODUCTION

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2. MODELS

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2.1 MODELS 4200 AND 4200L

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2.2 MODELS 4200-6 AND 4200-7

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2.3 MODEL 4202

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2.4 MODEL 4210

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3. PRIOR TO INSTALLATION

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3.1 ADJUSTING GAUGE TO THE DESIRED RANGE

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3.2 GAUGE AND CABLE ASSEMBLY

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3.3 PRELIMINARY CHECK

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4. INSTALLING THE GAUGES IN CONCRETE

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4.1 DIRECT ATTACHMENT TO REBAR

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4.2 SUSPENSION METHOD

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4.3 ALTERNATIVE SUSPENSION METHOD

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4.4 USING PRE-CAST BRIQUETTES, SHOTCRETE, OR GROUTING

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4.5 CABLE SPLICING AND TERMINATION

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4.6 LIGHTNING PROTECTION

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5. TAKING READINGS

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5.1 MICRO-6000 DATALOGGER

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5.2 EMBEDMENT STRAIN GAUGE READOUT POSITIONS

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5.3 GK-404 READOUT BOX

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5.3.1 OPERATING THE GK-404

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12

5.4 GK-405 READOUT BOX

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5.4.1 CONNECTING SENSORS WITH 10-PIN BULKHEAD CONNECTORS 

ATTACHED

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13

5.4.2 CONNECTING SENSORS WITH BARE LEADS

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13

5.4.3 OPERATING THE GK-405

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13

5.5 GK-403 READOUT BOX (OBSOLETE MODEL)

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14

5.5.1 CONNECTING SENSORS WITH 10-PIN BULKHEAD CONNECTORS 

ATTACHED

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14

5.5.2 CONNECTING SENSORS WITH BARE LEADS

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14

5.5.3 OPERATING THE GK-403

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14

5.6 MEASURING TEMPERATURES

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14

6. DATA REDUCTION

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15

Summary of Contents for 4200 Series

Page 1: ... 2018 GEOKON All rights reserved Document Revision BB Release date 12 4 18 Model 4200 Series Vibrating Wire Strain Gauges Instruction Manual ...

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Page 3: ...ON is not responsible for any damages or losses caused to other equipment whether direct indirect incidental special or consequential which the purchaser may experience as a result of the instal lation or use of the product The buyer s sole remedy for any breach of this agreement by GEOKON or any breach of any warranty by GEOKON shall not exceed the purchase price paid by the purchaser to GEOKON f...

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Page 5: ...E OR GROUTING 9 4 5 CABLE SPLICING AND TERMINATION 9 4 6 LIGHTNING PROTECTION 9 5 TAKING READINGS 11 5 1 MICRO 6000 DATALOGGER 11 5 2 EMBEDMENT STRAIN GAUGE READOUT POSITIONS 11 5 3 GK 404 READOUT BOX 11 5 3 1 OPERATING THE GK 404 12 5 4 GK 405 READOUT BOX 12 5 4 1 CONNECTING SENSORS WITH 10 PIN BULKHEAD CONNECTORS ATTACHED 13 5 4 2 CONNECTING SENSORS WITH BARE LEADS 13 5 4 3 OPERATING THE GK 405 ...

Page 6: ...OUS GROWTH 18 6 9 CONVERTING STRAIN TO LOAD 18 6 10 EFFECTIVE MODULUS 18 7 TROUBLESHOOTING 19 APPENDIX A SPECIFICATIONS 21 A 1 STRAIN GAUGE 21 A 2 THERMISTOR 21 APPENDIX B THEORY OF OPERATION 22 APPENDIX C THERMISTOR TEMPERATURE DERIVATION 24 APPENDIX D HIGH TEMPERATURE THERMISTOR LINEARIZATION 25 APPENDIX E NO STRESS STRAIN ENCLOSURE 26 APPENDIX F MODEL 4200HT T HIGH TEMPERATURE STRAIN GAUGE 28 A...

Page 7: ... FIGURE 7 MODEL 4210 VIBRATING WIRE STRAIN GAUGE 4 FIGURE 8 ADJUSTING THE RANGE OF THE STRAIN GAUGE 5 FIGURE 9 ASSEMBLED STRAIN GAUGE AND COIL HOUSING 5 FIGURE 10 ATTACHING GAUGES TO REBAR 7 FIGURE 11 SUSPENDING STRAIN GAUGES BETWEEN REBAR 8 FIGURE 12 ALTERNATIVE METHOD FOR ATTACHING GAUGES TO REBAR 8 FIGURE 13 LIGHTNING PROTECTION SCHEME 10 FIGURE 14 GK 404 READOUT 12 FIGURE 15 LEMO CONNECTOR TO ...

Page 8: ...IN GAUGE FACTORS 15 TABLE 5 STRAIN RESOLUTION 16 TABLE 6 EFFECTIVE MODULUS 18 TABLE 7 RESISTANCE WORK SHEET 20 TABLE 8 SAMPLE RESISTANCE 20 TABLE 9 STRAIN GAUGE SPECIFICATIONS 21 TABLE 10 EMBEDMENT STRAIN GAUGE THEORETICAL PARAMETERS 22 TABLE 11 THERMISTOR RESISTANCE VERSUS TEMPERATURE 24 TABLE 12 THERMISTOR RESISTANCE VERSUS TEMPERATURE FOR MODEL 4200HT 25 ...

Page 9: ...ON 5 TRUE LOAD RELATED STRAIN CORRECTED FOR TEMPERATURE 16 EQUATION 6 ACTUAL STRAIN 17 EQUATION 7 STRAIN TO LOAD FORMULA 18 EQUATION 8 RESISTANCE TO TEMPERATURE 24 EQUATION 9 HIGH TEMPERATURE RESISTANCE TO TEMPERATURE 25 EQUATION 10 TEMPERATURE INDUCED STRESS 29 EQUATION 11 COMBINED TEMPERATURE AND LOAD RELATED STRESS 29 EQUATION 12 EXTERNAL LOAD STRESS 29 EQUATION 13 ACTUAL STRAIN 29 ...

Page 10: ...VI ...

Page 11: ...red as a change in the resonant frequency of vibration of the wire Two coils one with a magnet insert the other with a pole piece insert are located close to the vibrating wire In use a pulse of varying frequency swept frequency is applied to the coils causing the wire to vibrate primarily at its resonant frequency Portable readouts and dataloggers are available from GEOKON These models when used ...

Page 12: ...ON 2 1 MODELS 4200 AND 4200L GEOKON Models 4200 and 4200L are designed primarily for long term strain measurements inside mass concrete in structures such as foundations piles bridges dams containment vessels tunnel liners etc The 4200L is a low modulus version designed to enable early curing strains to be measured The length of the 4200 gauge is 152 mm 6 FIGURE 2 Model 4200 Vibrating Wire Strain ...

Page 13: ...he small collar under the shrink tube at one end FIGURE 4 Model 4200 6 Vibrating Wire Strain Gauge FIGURE 5 Model 4200 7 Vibrating Wire Strain Gauge 2 3 MODEL 4202 Model 4202 is designed for direct embedment in grout mortar and small aggregate concrete It is also useful for model studies The length of the 4202 gauge is 50 mm 2 FIGURE 6 Model 4202 Vibrating Wire Strain Gauge Collar Collar ...

Page 14: ...esigned for embedment in large aggregate concrete greater than 3 4 of an inch The standard gauge length is 254 mm 10 other gauge lengths available include Model 4212 305 mm 12 and Model 4214 356 mm 14 FIGURE 7 Model 4210 Vibrating Wire Strain Gauge ...

Page 15: ...4000 microstrain FIGURE 8 Adjusting the Range of the Strain Gauge Model 4200 6 4200 7 Note Although the readings are taken on position D the digits shown must be converted to microstrain manually To do this multiply the observed digit change by the gauge factor given on the calibration sheet provided with the strain gauge 3 2 GAUGE AND CABLE ASSEMBLY Insert the flat part of the gauge into the slot...

Page 16: ...the two thermistor wires usually white and green Using Table 11 on page 24 convert the resistance to temperature Compare the result to the current ambient temperature For Model 4200HT see Table 12 on page 25 3 Connect the gauge to a readout box See readout instructions Section 5 Observe the displayed readout The reading should be about the midrange position as defined in Table 2 on page 11 4 Press...

Page 17: ...ie the instrument cable off to the rebar using nylon cable ties Note Don t tie the wires too tightly since rebar and tension cables tend to move during concrete placement and vibration Take care not to damage the cable with the vibrator The gauge can also be placed directly into the mix if it can be assured that the orientation will be correct after the gauge placement 4 2 SUSPENSION METHOD 1 Wrap...

Page 18: ...sing nylon cable ties as shown in the figure below Then tie the strain gauge to the short pieces of rebar again using more nylon cable ties This method avoids the resonance problems associated with the previous method FIGURE 12 Alternative Method for Attaching Model 4200 4200HT Strain Gauges to Rebar Instrument Cable Coil Assembly Rebar or Tensioned Cable Wire Tie Wire Tie Rubber Tape 4200 Wire Ti...

Page 19: ...e effect on gauge readings therefore splicing of cables has no ill effects and in some cases may be beneficial The cable used for making splices should be a high quality twisted pair type with 100 shielding and an integrated shield drain wire When splicing it is very important that the shield drain wires be spliced together Always maintain polarity by connecting color to color Splice kits recommen...

Page 20: ...ce the board in the event that the unit is damaged by a lightning strike A connection is made between the enclosure and earth ground to facilitate the passing of transients away from the gauge See the figure below Plasma surge arrestors can be epoxied into the instrument cable close to the sensor A ground strap then connects the surge arrestor to an earth ground such as a grounding stake or the re...

Page 21: ...ITIONS The following table indicates the readout position detail for each strain gauge model TABLE 3 Readout Positions The following sections describe how to take readings using readout equipment available from GEOKON 5 3 GK 404 READOUT BOX The Model GK 404 Vibrating Wire Readout is a portable low power hand held unit that is capable of running for more than 20 hours continuously on two AA batteri...

Page 22: ...OS button displayed as A through F The current reading set by the MODE button displayed as a numeric value followed by the unit of measure Temperature reading of the attached instrument in degrees Celsius Use the POS and MODE buttons to select the correct position and display units for the model of equipment purchased The GK 404 will continue to take measurements and display readings until the uni...

Page 23: ...hen twist the outer ring of the male connector until it locks into place 5 4 2 CONNECTING SENSORS WITH BARE LEADS Attach the GK 403 2 flying leads to the bare leads of a GEOKON vibrating wire sensor by connecting each of the clips on the leads to the matching colors of the sensor conductors with blue representing the shield bare 5 4 3 OPERATING THE GK 405 Press the power button on the Readout Unit...

Page 24: ...the instrument reading in degrees Celsius 5 Press the Store button to record the value displayed If the no reading displays or the reading is unstable see Section 5 for troubleshooting suggestions The unit will automatically turn off after two minutes to conserve power For more information consult the GK 403 manual 5 6 MEASURING TEMPERATURES All GEOKON vibrating wire transducers are equipped with ...

Page 25: ...E Reading for Models 4200 position D and 4202 position E are displayed on the readout box directly in microstrain based on the theoretical equation EQUATION 2 Theoretical Strain Where f is the frequency in digits G is the theoretical gauge factor equal to 3 304 for the 4200 gauge and 0 3910 for the 4202 gauge In practice the act of clamping shortens the vibrating wire slightly causing it to over r...

Page 26: ... concrete expanded by exactly the same amount as the wire the wire tension would remain constant and no correction would be necessary However the steel expansion coefficient is different from the concrete expansion coefficient Due to this difference a temperature correction is required equal to EQUATION 4 Correction for Temperature Effects on the Gauge Where T0 is the initial temperature T1 is the...

Page 27: ...ain levels of 4000 8000 and 12000 at five different temperature levels i e 40 20 0 20 40 and 60 degrees Celsius When using the polynomial expression to calculate the strain this correction factor must be applied to the current reading R1 The modified value of R1 is then inserted into the polynomial Thus the modified value of R1 to be inserted into the polynomial is R1 0 000401 R1 1 067 x T1 T0 6 6...

Page 28: ...ulus of the structural element in the appropriate units is the strain in microstrain A is the cross sectional area in the appropriate units When installing strain gauges in concrete piles it is standard practice to install them in pairs on either side of the neutral axis This allows any strains imposed by bending to be corrected by taking the average strain of the two gauges It is also standard pr...

Page 29: ...ng outside the specified compressive or tensile range of the instrument The gauge may have become too slack or too tight inspect the data to determine whether this is a possibility Is there a source of electrical noise nearby Likely candidates are generators motors arc welding equipment high voltage lines etc If possible move the instrument cable away from power lines and electrical equipment or i...

Page 30: ...0HT T 120 for Model 4200HT infinite infinite infinite Black 180 50 for Models 4202 4200HT T 120 for Model 4200HT N A infinite infinite infinite White infinite infinite N A 3000 at 25 C infinite Green infinite infinite 3000 at 25 C N A infinite Shield infinite infinite infinite infinite N A Vibrating Wire Sensor Lead Grid SENSOR NAME Red Black White Green Shield Red Black White Green Shield ...

Page 31: ...l 4200 4200 6 4200 7 4202 4204 4210 4212 4214 4200HT Range Nominal 3000 5 000 10 000 3000 Resolution 1 0 1 0 5 1 0 4 1 1 0 1 0 4 1 0 4 1 0 4 1 1 0 1 Calibration Accuracy 0 1 Full Scale Reading FSR 0 5 FSR 0 1 FSR Typical Batch Factor 0 98 N A 0 91 N A 0 95 N A N A 0 98 Batch Factor Accuracy 0 5 FSR N A 0 5 FSR System Accuracy 2 0 FSR2 Stability 0 1 Full Scale FS yr Linearity 0 5 FSR 0 3 FSR 0 5 FS...

Page 32: ...quency of vibration of a wire is related to its tension length and mass The fundamental frequency may be determined by the equation Where Lw is the length of the wire in inches F is the wire tension in pounds m is the mass of the wire per unit length pounds seconds2 inches2 2 Note that Where W is the weight of Lw inches of wire in pounds g is the acceleration of gravity 386 inches seconds2 3 And W...

Page 33: ... the body must equal the deformation of the wire Where Ɛ is the strain in the body Lg is the gauge length in inches 11 Combining the equations from steps nine and ten gives Where for Model 4200 Lw is 5 875 inches Lg is 6 000 inches 12 Therefore 13 The display on position D of the readout is based on the equation The squaring inverting and multiplication by the factor 3 304 109 is all done internal...

Page 34: ...1 2 1475 42 353 4 82 110 8 122 82 87K 37 8417 3 1418 43 342 2 83 107 9 123 77 66K 36 8006 4 1363 44 331 5 84 105 2 124 72 81K 35 7618 5 1310 45 321 2 85 102 5 125 68 30K 34 7252 6 1260 46 311 3 86 99 9 126 64 09K 33 6905 7 1212 47 301 7 87 97 3 127 60 17K 32 6576 8 1167 48 292 4 88 94 9 128 56 51K 31 6265 9 1123 49 283 5 89 92 5 129 53 10K 30 5971 10 1081 50 274 9 90 90 2 130 49 91K 29 5692 11 104...

Page 35: ... 1 530 74 571 2 106 247 0 138 119 4 170 63 3 202 36 2 234 18 971 11 4 725 43 1 480 75 555 3 107 241 1 139 116 9 171 62 1 203 35 6 235 18 090 12 4 543 44 1 432 76 539 9 108 235 3 140 114 5 172 61 0 204 35 1 236 17 255 13 4 368 45 1 385 77 525 0 109 229 7 141 112 1 173 59 9 205 34 5 237 16 463 14 4 201 46 1 340 78 510 6 110 224 3 142 109 8 174 58 8 206 33 9 238 15 712 15 4 041 47 1 297 79 496 7 111 ...

Page 36: ...e can be used to apply corrections for these phenomena to the other strain gauges in the mass concrete allowing the user to quantify only those strains that result from stress changes INSTALLING THE 4200 4 ENCLOSURE 1 Position the enclosure inside the concrete mass with the top open so that it can be easily filled with concrete Often the 4200 4 will be placed next to a strain gauge rosette 2 Mount...

Page 37: ...sing another tie wire and the second set of holes in the enclosure 6 Arrange the instrument cable so that it exits through the top of the enclosure 7 When pouring concrete into the enclosure remove aggregate that is too large Be careful not to disturb the gauges during the filling process ...

Page 38: ... 17 3 C Coil resistance for Model 4200HT T is 50 ohms The thermistor included with the gauge is a high temperature thermistor which uses the resistance to temperature conversion table shown in Table 12 on page 25 When using a readout box it is not necessary to connect the green and white wires to the readout because the temperature shown on the readout will be incorrect Instead use a digital ohmme...

Page 39: ...hanges the resulting graph will show a straight line relationship the slope of which yields a factor KT microstrain degree This factor can be used to calculate the temperature induced stress as shown by the following equation σ temperature induced KT T1 T0 E EQUATION 10 Temperature Induced Stress This can be subtracted if desired from the combined load related stress change using the following equ...

Page 40: ...in in the concrete slab On the other hand if the concrete slab is free of all restraint and experiences a temperature change of 1 C then the concrete would expand 10 microstrains while the vibrating wire would expand 12 2 microstrains The value of R1 R0 B would then be 2 2 microstrains the vibrating wire would slacken slightly and Equation 5 would yield a value of 10 microstrains ...

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Page 44: ...GEOKON 48 Spencer Street Lebanon New Hampshire 03766 USA Phone 1 603 448 1562 Email info geokon com Website www geokon com GEOKON is an ISO 9001 2015 registered company ...

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