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Geokon 3400 Series, Instruction Manual

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Geokon 3400 Series Instruction Manual Download Page 21

  15 

5.5 Calibration 

 
Calibration Reports are supplied with the sensors. Typical calibration reports for the three types 
of Model 3400 semiconductor piezometers are shown in Figure 9, Figure 10, and Figure 11. 
 

 

Figure 9 - Typical Calibration Report for Model 3400-1 with 100mV Output 

 

 

Summary of Contents for 3400 Series

Page 1: ...means without the written consent of Geokon Inc The information contained herein is believed to be accurate and reliable However Geokon Inc assumes no responsibility for errors omissions or misinterpretation The information herein is subject to change without notification Copyright 1983 2018 by Geokon Inc REV H 02 12 2018 ...

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Page 3: ...re are no warranties except as stated herein 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 Geokon Inc 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 t...

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Page 5: ...4 6 MODEL 3400H TRANSDUCER 11 4 7 SPLICING AND JUNCTION BOXES 11 4 8 ELECTRICAL NOISE 12 4 9 FREEZING PROTECTION 12 4 10 LIGHTNING PROTECTION 12 5 READOUT PROCEDURES 14 5 1 INITIAL READINGS 14 5 2 INPUT VOLTAGE 14 5 3 CONVERTING TO PRESSURES 14 5 4 MEASURING TEMPERATURES 14 5 5 CALIBRATION 15 6 DATA REDUCTION 18 6 1 PRESSURE CALCULATION 18 6 2 TEMPERATURE CORRECTION 19 6 3 BAROMETRIC CORRECTIONS 1...

Page 6: ...EL 3400 1 WITH 100MV OUTPUT 15 FIGURE 10 TYPICAL CALIBRATION REPORT FOR MODEL 3400 2 WITH 0 TO 5 VOLT OUTPUT 16 FIGURE 11 TYPICAL CALIBRATION REPORT FOR MODEL 3400 3 WITH 4 TO 20MA OUTPUT 17 TABLES TABLE 1 CEMENT BENTONITE WATER RATIOS 7 TABLE 2 ENGINEERING UNITS MULTIPLICATION FACTORS 18 TABLE 3 MODEL 3400 SPECIFICATIONS 20 TABLE 4 OUTPUT UNITS SPECIFICATIONS 21 TABLE 5 THERMISTOR RESISTANCE VERS...

Page 7: ...ggressive environments At one end of this tube is a filter housing to allow the passage of water while preventing the entry of soil particles At the other end is located a bulkhead seal and cable entry seal to prevent water from reaching the backside of the transducer A thermistor included inside the main housing allows the measurement of temperature The output cable is multi conductor with from t...

Page 8: ...d the shield The resistance should be greater than 50 megohms If an attempt is made to check the calibration make sure that the applied pressure is accurate Be aware that calibrations performed by raising and lowering the piezometer inside a borehole or well can be compromised by a displacement of the water level caused by changing volumes of immersed cable Calibrations performed in this way shoul...

Page 9: ...essure sensitive diaphragm After a period of time this air will dissolve into the water filling the filter and the space above it entirely with water To speed up the saturation process remove the filter from the piezometer by carefully twisting and pulling on the filter housing assembly or unscrewing the point of the piezometer for model 3400DP Hold the piezometer with the filter facing up and fil...

Page 10: ...When maximum vacuum has been achieved allow de aired water to enter the chamber until it reaches an elevation a few inches above the piezometer filter 4 Close off the inlet port 5 Release the vacuum 6 Observe the transducer output It may take up to 24 hours for the filter to completely saturate and the pressure to rise to zero 7 After saturation the transducer should be kept in a container of de a...

Page 11: ...6 to 12 inches below the proposed piezometer location Boreholes should be drilled without using drilling mud or by using a material that degrades rapidly with time such as Revert Wash the borehole clean of drill cuttings Backfill the borehole with clean fine sand to a point six inches below the desired piezometer tip location The piezometer can then be lowered into position Preferably the piezomet...

Page 12: ... using a bentonite cement grout only However good results have been obtained by placing the piezometer inside a canvas bag filled with sand before grouting The general rule for installing piezometers in this way is to use a bentonite grout that mimics the strength of the surrounding soil The emphasis should be on controlling the water to cement ratio This is accomplished by mixing the cement with ...

Page 13: ... the bottom of the borehole should be avoided It is good practice to read the piezometer while pumping For more details on grouting refer to Piezometers in Fully Grouted Boreholes by Mikkelson and Green FMGM proceedings Oslo 2003 Copies are available from Geokon 4 3 Installation in Fills and Embankments Geokon piezometers are normally supplied with direct burial cable suitable for placement in fil...

Page 14: ...etween the pore air pressure and the pore water pressure The difference between these two pressures is due to the capillary suction in the soil The consensus is that the difference is normally of no consequence to embankment stability The coarse tip filter is suitable for most routine measurements Both the installation shown in Figure 3 and the installation shown in Figure 4 may be used with the s...

Page 15: ...oils it is possible to drill a hole and then push the 3400DP only a few feet below the bottom of the hole but if the soil is too stiff the sensor may overrange or break The piezometer should be connected to a readout box and monitored during the installation process If pressures reach or exceed the calibrated range the installation should be stopped Allow the pressure to dissipate before continuin...

Page 16: ...pe well 4 Be sure the cable is securely fastened to prevent the piezometer from sliding further into the well and causing an error in the readings Figure 6 Typical Level Monitoring Installation It is not recommended that piezometers be installed in wells or standpipes where an electrical pump or cable is nearby Electrical interference from these sources can cause unstable readings If unavoidable i...

Page 17: ...er 4 7 Splicing and Junction Boxes Cable splicing should be kept to a minimum since changes in cable resistance can cause changes in calibration if remote sensing techniques or 4 20 mA output are not in use The Model 3400 utilizes a semiconductor transducer and as such has low level output signals If cables are damaged or improperly spliced the outputs can be seriously degraded Therefore it is abs...

Page 18: ... cause a problem obtaining a stable reading Contact the factory concerning filtering options available for use with the Geokon dataloggers and readouts should difficulties arise 4 9 Freezing Protection If the water around the piezometer freezes this could damage the piezometer diaphragm causing a large shift in the zero pressure reading If the piezometer is to be used in locations that are subject...

Page 19: ...e to the installed piezometer see Figure 8 This is the recommended method of lightning protection Piezometer Piezometer Cable To Terminal Box Readout Equipment Lightning Arrestor Board LAB 3 in special enclosure Ground Stake Ground Connection accessible from surface Figure 8 Recommended Lightning Protection Scheme ...

Page 20: ...h linear and polynomial expressions are shown For better accuracy the polynomial expression should be used with a proviso that the value for the C coefficient be derived in the field by taking an initial reading when the sensor is subject to atmospheric pressures only as described in Section 4 1 Then substituting this initial value into the formula and setting the value of P to zero will yield the...

Page 21: ...ts are supplied with the sensors Typical calibration reports for the three types of Model 3400 semiconductor piezometers are shown in Figure 9 Figure 10 and Figure 11 Figure 9 Typical Calibration Report for Model 3400 1 with 100mV Output ...

Page 22: ...16 Figure 10 Typical Calibration Report for Model 3400 2 with 0 to 5 Volt Output ...

Page 23: ...17 Figure 11 Typical Calibration Report for Model 3400 3 with 4 to 20mA Output ...

Page 24: ... H2O H2O mm H20 m H20 HG mm HG atm mbar bar kPa MPa psi 1 036127 43275 0014223 1 4223 49116 019337 14 696 014503 14 5039 14503 145 03 H2O 27 730 1 12 039372 39 372 13 596 53525 406 78 40147 401 47 4 0147 4016 1 H2O 2 3108 08333 1 003281 3 281 1 133 044604 33 8983 033456 33 4558 3346 334 6 mm H20 704 32 25 399 304 788 1 1000 345 32 13 595 10332 10 197 10197 101 97 101970 m H20 70432 025399 304788 0...

Page 25: ...ers and antennas Make sure the shield drain wire is connected to ground whether using a portable readout or datalogger Does the readout work with another piezometer If not the readout may have a low battery or be malfunctioning Consult the appropriate readout manual for charging or troubleshooting directions Is the filter clogged Remove piezo if possible and inspect Symptom Piezometer Fails to Rea...

Page 26: ...r elec codes 2 D G 3 20 to 50 C 5 to 125 F for elec codes F M P Amplified units 100C maximum 24 Vdc supply Zero Tolerance 1 of span Span Tolerance 1 of span Mechanical Configuration Pressure Port see ordering chart Wetted Parts 17 4 PH Stainless Steel Electrical Connection see ordering chart Enclosure 316 ss 17 4 PH ss IP65 for elec codes A B C D G 1 2 3 IP67 for elec code F IP68 for elec codes M ...

Page 27: ... Voltage Vs 10Vdc 7 35 Vdc 6mA Supply Voltage Sensitivity 0 01 FS Volt Min Load Resistance FS output 2 kohms Current Output Units Output 4 20mA 2 wire Supply Voltage VS 24 Vdc 7 35 Vdc Supply Voltage Sensitivity 0 01 FS Volt Max Loop Resistance Vs 7 x 50 ohms Table 4 Output Units Specifications A 2 Thermistor See Appendix B also Range 80 to 150 C Accuracy 0 5 C ...

Page 28: ...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 1040 51 266 6 91 87 9 131 46 94K 28 5427 12 1002 52 258 6 92 85...

Page 29: ...nnected internally C 2 Zero to Five Volt DC Output Geokon Cable 04 375V9 Violet Internal Sensor Wiring Function Description Red Red Power Red s Black Black Power White White Signal White s Black Black Signal Blue N C Thermistor Blue s Black N C Thermistor Shields 5 N C Ground Table 7 0 5VDC Output Wiring Note Input voltage for Model 3400 2 0 5VDC output is 6 5 35V d c C 3 Four to 20 Milliamp Outpu...

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