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Geokon 4580, Instruction Manual

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Geokon 4580 Instruction Manual Download Page 19

  13 

4.3.1 Vented Transducers 

 

Vented transducers are designed to eliminate barometric effects. The space inside the 

transducer is not hermetically sealed and evacuated (see Figure 1) but is connected via a 

tube (integral with the cable) to the atmosphere. A chamber containing desiccant capsules 

is attached to the end of the tube to prevent moisture from entered the transducer cavity. 

As supplied, the outer end of the desiccant chamber is closed by means of a seal screw to 

keep the desiccant fresh during storage and transportation. 

THE SEAL SCREW MUST 

BE REMOVED BEFORE THE TRANSDUCER IS PUT INTO SERVICE! 

The 

desiccant capsules are blue when fresh, they will gradually turn pink as they absorb 

moisture. When they have turned light pink in color they should be replaced. Contact 

Geokon for replacement capsules. 

 

4.4 Environmental Factors 

 

Since the purpose of the transducer installation is to monitor site conditions, factors that can 

affect these conditions should always be observed and recorded. Seemingly minor effects can 

have a real influence on the behavior of the structure being monitored and can give an early 

indication of potential problems. Some of the factors include, but are not limited to; blasting, 

rainfall, tidal levels, excavation and fill levels and sequences, traffic, temperature and barometric 

changes (and other weather conditions), changes in personnel, nearby construction activities, 

seasonal changes, etc. 

 

 

Summary of Contents for 4580

Page 1: ... by any means without the written consent of Geokon The information contained herein is believed to be accurate and reliable However Geokon assumes no responsibility for errors omissions or misinterpretation The information herein is subject to change without notification Copyright 1995 2019 by Geokon Doc Rev Q 04 30 19 ...

Page 2: ......

Page 3: ...nnel There 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 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 ...

Page 4: ......

Page 5: ...he GK 405 7 3 3 GK 403 READOUT BOX OBSOLETE MODEL 8 3 3 1 Connecting Sensors with a 10 pin Bulkhead 8 3 3 2 Connecting Sensors with Bare Leads 8 3 3 3 Operating the GK 403 8 3 4 MEASURING TEMPERATURES 8 4 DATA REDUCTION 9 4 1 PRESSURE CALCULATION 9 4 2 TEMPERATURE CORRECTION 11 4 3 BAROMETRIC CORRECTION 11 4 3 1 Vented Transducers 13 4 4 ENVIRONMENTAL FACTORS 13 5 MAINTENANCE 14 6 TROUBLESHOOTING ...

Page 6: ...ADINGS 7 FIGURE 7 SAMPLE MODEL 4580 CALIBRATION REPORT 19 TABLES TABLE 1 ENGINEERING UNITS MULTIPLICATION FACTORS 10 TABLE 2 MODEL 4580 PRESSURE TRANSDUCER SPECIFICATIONS 16 TABLE 3 THERMISTOR RESISTANCE VERSUS TEMPERATURE 17 EQUATIONS EQUATION 1 DIGITS CALCULATION 9 EQUATION 2 CONVERT DIGITS TO PRESSURE 9 EQUATION 3 TEMPERATURE CORRECTION 11 EQUATION 4 BAROMETRIC CORRECTION 11 EQUATION 5 CORRECTE...

Page 7: ...ic effects need to be eliminated such as in the weir and stream level measurements In the case where the sensor is used as a barometer the capsule is evacuated The vibrating wire is attached to the capsule on one end and to the rigid housing on the other External pressure applied to the capsule causes it to compress and exert a force on the vibrating wire gauge and this produces a change in wire t...

Page 8: ...etween the sensor being vertically up and vertically down is normal This phenomenon will not be a problem if the sensor remains stationary or is in the same orientation during use Additionally these sensors are sensitive to shock particularly the very low pressure versions A shift in the zero reading can occur during shipping or rough handling Normally this will not affect the operation of the sen...

Page 9: ...th the transducers held under water to prevent air from reentering the sensor Air trapped in the chamber can cause inaccurate and or unstable pressure readings in changing temperature environments The vented versions incorporate a moisture trap on the end of the vent line Desiccant inside the moisture trap prevents moisture from entering the inside of the sensor capsule The vent trap screw must be...

Page 10: ...r these types of installations it is recommended that the transducer be supplied with enough cable to reach the installation depth plus extra cable to pass through drilling equipment rods casing etc Cable used for making splices should be a high quality twisted pair type with 100 shielding and an integral shield drain wire When splicing it is very important that the shield drain wires be spliced t...

Page 11: ...nal boxes available from Geokon can be ordered with lightning protection built in The terminal board used to make the gauge connections has provision for the installation of plasma surge arrestors Lightning Arrestor Boards LAB 3 can also be incorporated into the terminal box The terminal box must be connected to an earth ground for these levels of protection to be effective If the instruments will...

Page 12: ...rs of the sensor conductors with blue representing the shield bare To turn the GK 404 on press the ON OFF button on the front panel of the unit The initial startup screen will be displayed After approximately one second the GK 404 will start taking readings and display them based on the settings of the POS and MODE buttons The unit display from left to right is as follows The current Position Set ...

Page 13: ...rs 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 3 2 3 Operating the GK 405 Press the button labeled POWER ON A blue light will begin blinking signifying that the Remote Module is waiting to connect to the handhel...

Page 14: ...yed above the gauge reading in degrees centigrade 5 Press the Store button to record the value displayed If the no reading displays or the reading is unstable see Section 6 for troubleshooting suggestions The unit will automatically turn off after approximately two minutes to conserve power Consult the GK 403 Instruction Manual for additional information 3 4 Measuring Temperatures All vibrating wi...

Page 15: ...ssure To convert digits to pressure using a linear calibration coefficient the following equation applies See Appendix C for use of second order polynomial Puncorrected R1 R0 G F1 Equation 2 Convert Digits to Pressure Where R0 represents the initial reading taken at installation usually the zero reading R1 represents the current reading G is the calibration factor required to convert from digits t...

Page 16: ...000133 101320 0001 1 001 1 Table 1 Engineering Units Multiplication Factors Note Due to changes in specific gravity with temperature the factors for mercury and water in the above table are approximate In the special case where the Model 4580 is being used as a Barometer it is necessary to add the atmospheric pressure at the time of the initial reading This pressure would best be obtained locally ...

Page 17: ...tial temperature K is the thermal coefficient from the supplied calibration report F1 is an optional multiplier to convert to engineering units see Table 1 The calculated correction would then be added to the Pressure calculated using Equation 2 If the engineering units were converted remember to apply the same conversion to the calculated temperature correction 4 3 Barometric Correction Since the...

Page 18: ...ion is to use pressure transducers that are vented to the atmosphere as described in Section 4 3 1 With vented transducers barometric pressure finds its way to both the inside and the outside of the pressure capsule and is thus automatically canceled Equation 5 describes the pressure calculation with both temperature and barometric corrections applied Pcorrected R1 R0 G T1 T0 K S1 S0 F2 Equation 5...

Page 19: ...desiccant capsules are blue when fresh they will gradually turn pink as they absorb moisture When they have turned light pink in color they should be replaced Contact Geokon for replacement capsules 4 4 Environmental Factors Since the purpose of the transducer installation is to monitor site conditions factors that can affect these conditions should always be observed and recorded Seemingly minor ...

Page 20: ...e sensor is installed in water with high concentrations of silts etc it may require cleaning from time to time This can be accomplished by gently flushing water through the transducer first through the P 1 port and then back through the seal screw hole Repeat this several times until the water passing through is clear Remember not to apply excess pressure to the sensor ...

Page 21: ...adings automatically are the swept frequency excitation settings correct Try reading the transducer on a different readout position For instance channel A of the GK 404 and GK 405 might be able to read the sensor To convert the Channel A period display to digits use Equation 1 in Section 4 1 Is there a source of electrical noise nearby Most probable sources of electrical noise are motors generator...

Page 22: ...ength 110 mm 4 33 172 mm 6 75 172 mm 6 75 112 mm 4 5 Weight 1 3 kg 2 8 lbs 1 5 kg 3 3 lbs 2 0 kg 4 4 lbs 4 0 kg 9 0 lbs Table 2 Model 4580 Pressure Transducer Specifications Notes Other ranges available upon request The accuracy of the calibration equipment 0 1 FS linearity available upon request Also 0 1 accuracy can be achieved by using a second order polynomial instead of a linear calibration f...

Page 23: ... 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 8...

Page 24: ...nts shown on the calibration report are those developed under the conditions of temperature and barometric pressure experienced at the time of the calibration and which are shown on the calibration report Theoretically these could be used as is but it is always good practice to establish and use zero conditions at the site since the zero may have shifted slightly due to rough handling during shipm...

Page 25: ...19 APPENDIX D TYPICAL CALIBRATION REPORT Figure 7 Sample Model 4580 Calibration Report ...

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