Geokon 4650 User manual

Instruction Manual
Model 4650
VW Settlement Sensor
No part of this instruction manual may be reproduced, 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 © 1984-2018 by Geokon®
(Doc Rev S, 12/19/18)

Warranty Statement
Geokon warrants its products to be free of defects in materials and workmanship, under normal
use and service for a period of 13 months from date of purchase. If the unit should malfunction,
it must be returned to the factory for evaluation, freight prepaid. Upon examination by Geokon,
if the unit is found to be defective, it will be repaired or replaced at no charge. However, the
WARRANTY is VOID if the unit shows evidence of having been tampered with or shows
evidence of being damaged as a result of excessive corrosion or current, heat, moisture or
vibration, improper specification, misapplication, misuse or other operating conditions outside of
Geokon's control. Components which wear or which are damaged by misuse are not warranted.
This includes fuses and batteries.
Geokon manufactures scientific instruments whose misuse is potentially dangerous. The
instruments are intended to be installed and used only by qualified personnel. 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 of the installation 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 for the unit or units, or equipment directly affected by
such breach. Under no circumstances will Geokon reimburse the claimant for loss incurred in
removing and/or reinstalling equipment.
Every precaution for accuracy has been taken in the preparation of manuals and/or software,
however, Geokon neither assumes responsibility for any omissions or errors that may appear nor
assumes liability for any damages or losses that result from the use of the products in accordance
with the information contained in the manual or software.

TABLE of CONTENTS
1. GENERAL DESCRIPTION...................................................................................................................................1
2. INSTALLATION PROCEDURES ........................................................................................................................3
2.1 INSTALLING THE SENSOR .....................................................................................................................................3
2.2 INSTALLING THE CABLES AND LIQUID FILLED TUBES .........................................................................................3
2.3 INSTALLING THE RESERVOIR,CONNECTING THE SENSOR TUBES AND VENT TUBE .............................................4
2.4 INITIAL READINGS ...............................................................................................................................................5
3. TAKING READINGS.............................................................................................................................................6
3.1 GK-404 READOUT BOX.......................................................................................................................................6
3.2 GK-405 READOUT BOX.......................................................................................................................................7
3.2.1 Connecting Sensors with 10-pin Bulkhead Connectors Attached ...............................................................7
3.2.2 Sensors with Bare Leads .............................................................................................................................7
3.2.3 Operating the GK-405 ................................................................................................................................7
3.3 GK-403 READOUT BOX (OBSOLETE MODEL)......................................................................................................8
3.3.1 Connecting Sensors with 10-pin Bulkhead Connectors Attached ...............................................................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 CALCULATION OF SENSOR ELEVATION................................................................................................................9
4.2 CORRECTION FOR SETTLEMENT OR HEAVE OF THE RESERVOIR TERMINAL .......................................................10
4.3 CORRECTIONS FOR TEMPERATURE ....................................................................................................................10
5. SPECIAL TOOLS AND APPARATUS REQUIRED FOR VARIOUS TEST PROCEDURES....................12
6. FLUSHING PROCEDURES................................................................................................................................12
7. PURGING THE VENT LINES............................................................................................................................13
8. IN SITU CALIBRATION.....................................................................................................................................14
9. IN SITU ZERO CHECK ......................................................................................................................................15
10. MAINTENANCE ................................................................................................................................................15
11. TROUBLE SHOOTING .....................................................................................................................................16
11.1 UNSTABLE READINGS......................................................................................................................................16
11.2 READING OF 9999 ............................................................................................................................................16
11.3 SUDDEN OR LARGE CHANGES IN READINGS ....................................................................................................16
APPENDIX A. SPECIFICATIONS.........................................................................................................................17
A.1 MODEL 4650 VW SETTLEMENT SENSOR ..........................................................................................................17
A.2 THERMISTOR (SEE APPENDIX BALSO) ..............................................................................................................17
APPENDIX B. THERMISTOR TEMPERATURE DERIVATION.....................................................................18
APPENDIX C. SPLICING 4650 SETTLEMENT SENSOR TUBING AND CABLE ........................................19
C.1 REPLACING A TRANSDUCER..............................................................................................................................19
C.1.1 Liquid Line ...............................................................................................................................................19
C.1.2 Splicing the Cable ....................................................................................................................................20
C.2 ADDING AN EXTENSION TO A SENSOR ASSEMBLY ............................................................................................20
APPENDIX D. SWAGELOK TUBE FITTING INSTRUCTIONS ......................................................................21
D.1 INSTALLATION ..................................................................................................................................................21
D.2 REASSEMBLY INSTRUCTIONS ............................................................................................................................22

FIGURES
Figure 1 - Typical Installation of Vibration Wire Settlement System .......................................................................... 1
Figure 2 - Sensor Details .............................................................................................................................................. 1
Figure 3 - Reservoir Details.......................................................................................................................................... 2
Figure 4 - Lemo Connector to GK-404......................................................................................................................... 6
Figure 5 - Live Readings – Raw Readings ................................................................................................................... 7
Figure 6 - Typical Calibration Report..........................................................................................................................11
Figure 7 - Flushing Apparatus .....................................................................................................................................12
Figure 8 - In Situ Calibration Apparatus......................................................................................................................14
Figure 9 - Tube Insertion .............................................................................................................................................21
Figure 10 - Make a Mark at Six O’clock .....................................................................................................................21
Figure 11 - Tighten One and One-Quarter Turns.........................................................................................................21
Figure 12 - Marks for Reassembly...............................................................................................................................22
Figure 13 - Ferrules Seated Against Fitting Body .......................................................................................................22
Figure 14 - Tighten Nut Slightly..................................................................................................................................22
TABLES
Table 1 - Specifications ...............................................................................................................................................17
Table 2 - Thermistor Resistance versus Temperature..................................................................................................18
EQUATIONS
Equation 1 - Elevation .................................................................................................................................................. 9
Equation 2 - Elevation, corrected for temperature .......................................................................................................10
Equation 3 - Resistance to Temperature ......................................................................................................................18

1
1. GENERAL DESCRIPTION
The 4650 Settlement System is designed to measure the differential settlement between two
points. A reservoir is located at a stable reference point and is connected to a sensor located at
the settlement point by two liquid filled tubes. The sensor senses the pressure of liquid within the
tube. This provides a measure of the height of the liquid column, which in turn gives a
measurement of the elevation difference between the reservoir and the sensor.
Figure 1 shows a typical installation used to measure the settlement inside an embankment. The
sensor is read by means of an electrical cable extending to the readout location. Readings may be
taken using a readout box or datalogger.
Figure 1 - Typical Installation of Vibration Wire Settlement System
The sensor (Figure 2) contains a thermistor for measurement of temperature as well as gas
discharge tubes for protection against lightning damage. The cable contains a vent tube that
connects the air inside the sensor to the space above the reservoir. This ensures that the sensor
readings are unaffected by any changes in barometric pressure. A desiccant chamber located at
the reservoir end of the vent line prevents moisture from migrating into the line.
Figure 2 - Sensor Details

2
Figure 3 shows details of a typical reservoir system. Two liquid filled tubes are provided for each
sensor and more than one sensor can be connected to a single reservoir. The use of two liquid
filled tubes permits the tubing to be flushed periodically to remove any accumulation of air
bubbles. With this type of liquid settlement sensor, it is vital that there be no air bubbles in the
liquid line. The liquid used is typically a de-aired antifreeze mixture, which resists the growth of
algae and is not susceptible to freezing.
Figure 3 - Reservoir Details

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2. INSTALLATION PROCEDURES
Most installations are in fills and embankments where the sensor and cables are buried.
Elsewhere the cables and sensors may be attached directly to structures undergoing settlement of
heave. The reservoir location must always be at a higher elevation then the sensor and higher
than any part of the liquid filled connecting tube.
Prefilled systems are usually delivered with de-aired antifreeze solution already in the liquid
lines. An extra length of small diameter tubing is connected to the outer ends of the liquid lines
to allow the system to breath during transportation while simultaneously protecting the sensor
from being overranged by temperature or pressure fluctuations and preventing the entry of air
bubbles into the main liquid lines.
Alternatively, systems may be provided with the tubing empty for filling in the field.
2.1 Installing the Sensor
The sensor is usually attached to a settlement plate using the bracket(s) provided.
The settlement plate may be attached directly to a structure using bolts. In the case of installation
in fills, a smooth, flat bottomed excavation should be made about 300 to 600 mm (12 to 24")
deep. The sensor plate is placed on this flat surface and covered with fine material, similar to the
fill, with all particles over 10 mm (0.4") in size removed. This material should be tamped down
around the cell until the excavation is filled back to the original ground surface. The elevation of
the settlement plate should be measured at the time of the installation using conventional level
survey techniques. Check also that the sensor is still functioning after tamping.
2.2 Installing the Cables and Liquid Filled Tubes
Cables and tubing need to be placed in a trench approximately 300 to 600 mm (12 to 24") deep.
The trench should not undulate and individual cables and tubes should be laid side by side
without touching or crossing each other. In no place should the tubing be higher than the
reservoir location. Before backfilling the trench, examine the tubing for signs of air bubbles: If
any are noted, the tubing will need to be flushed before initial readings are taken.
Compact the material in the trench around the cables. Do not allow large angular pieces of rock
to rest directly on the cable. To prevent migration of water along the trench, bentonite plugs can
be constructed at intervals.
Trenches in earth dam embankments should never penetrate entirely through the clay core.
Compaction of the fill above the cables can proceed in a normal manner when the cover exceeds
600 mm (24") depth. Where cables are not buried, they should be adequately supported along
their length to prevent undulations. They should also be protected from direct sunlight and
insulated from rapid temperature fluctuations by encasing them in Styrofoam or urethane foam,
etc.

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2.3 Installing the Reservoir, Connecting the Sensor Tubes and Vent Tube
The reservoir should be installed on stable ground or at a location that can be level surveyed. The
terminal housing should be affixed to stakes grouted firmly into the ground or preferably into a
concrete pad poured at a location. The elevation of the reservoir pad should be surveyed and
recorded at the time of installation. The reservoir should never be located where it is exposed to
direct sunlight.
To fill the reservoir first make sure that the valve at the bottom is closed, then completely
remove the vent line Swagelok fitting from the top and half-fill the reservoir with antifreeze
solution (supplied) using the syringe supplied. To avoid foaming, poke the tube from the syringe
to the bottom of the reservoir and keep it below the surface of the liquid while filling.
The sensor tubes are shipped full of de-aired antifreeze solution. One tube is capped and to the
other tube is attached a long small diameter breather tube which is also full of antifreeze
solution. The purpose of the breather tube is to prevent air from entering into the sensor tube
during shipment while at the same time allowing the barometric pressure to equalize inside and
outside the sensor. It ensures that when the cap and the breather tube are removed from the ends
of the sensor tubing air is not sucked into the tubing by a built-up negative pressure. When
connecting the tubes from the sensor to the reservoir do not allow air to be trapped inside the
tubing.
Installation is as follows:
1) With the reservoir valve closed, remove one of the caps from the fitting at the base of the
reservoir, as well as the cap that does not have the breather tube from the end of the sensor
tube.
2) Make sure that water is oozing out of the tube. (Elevate the breather tube if necessary.)
3) Open the reservoir valve slightly so that water dribbles out.
4) Connect the tube fitting to the mating reservoir fitting and tighten one turn only.
5) Remove the breather tube from the end of the other sensor tube. (Make sure that water is
oozing out of the tube.)
6) Remove the second cap from the other fitting on the base of the reservoir.
7) Slightly open the reservoir valve.
8) While the water is dribbling out connect the second sensor tube fitting and tighten.
9) Remove the cap from the end of the vent line.
10) Make sure that the vent line to the sensor is not blocked. This can be checked using an
aspirator bulb, (or simply by sucking), to draw a vacuum on the vent line while observing the
sensor reading change on the GK-403, GK-404 or GK-405 readout box.
11) Attach the vent line to the vent line manifold using the Swagelok fittings. Follow the
instructions in Appendix D to ensure the Swagelok fittings are tightened properly!

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12) Add fresh desiccant to the desiccant chamber (or the vent line manifold).
13) Add more liquid to the reservoir to bring up to the half-full point. A few drops of light oil
added through the top of the reservoir will prevent evaporation from the liquid surface.
14) Reconnect the vent line fitting to the top of the reservoir.
15) Connect the sensor cable to the terminal panel (if one exists) as follows: Black and Red wires
to the gauge position, Green and White wires to the thermistor (temperature) position.
Manual switch panels can be used in conjunction with GK-403, GK-404, or GK-405 readout
boxes. Terminal strips are used in conjunction with dataloggers.
2.4 Initial Readings
Initial readings must be taken with great care; they are the base line readings to which all
subsequent readings are compared. It is important that the liquid filled tubes be at a constant
temperature. If the tubes are not completely buried the readings should be taken at a time when
the temperature is relatively constant. The readings should never be taken when the tubes are
exposed to direct sunlight. In addition, there should be no air bubbles in the liquid tubes. If air
bubbles are detected the tubes should be flushed before the initial readings are taken. If there is
any doubt, take readings, flush the tubing, and take readings again. Repeat if necessary until the
readings are stable. (See Section 3 for readout instructions.) Always record the ambient
temperature when taking readings.
Take careful measurement of the elevation of the liquid level inside the reservoir sight tube.
Make a mark on the tube opposite the liquid level. This will serve as a quick visual check on any
fluctuations and enable a quick means of measuring the magnitude of the change. For correction
of subsequent calculations of settlement, see Section 4. (Reservoir level fluctuations may be due
to temperature or pressure fluctuations or due to leakage.)

6
3. TAKING READINGS
When taking sensor readings also record the height of the fill above the sensor, the temperature,
and any other physical phenomena or construction activity that might affect the readings.
3.1 GK-404 Readout Box
The Model GK-404 Vibrating Wire Readout is a portable, low-power, handheld unit that is
capable of running for more than 20 hours continuously on two AA batteries. It is designed for
the readout of all Geokon vibrating wire gauges and transducers, and is capable of displaying the
reading in either digits, frequency (Hz), period (µs), or microstrain (µε). The GK-404 also
displays the temperature of the transducer (embedded thermistor) with a resolution of 0.1 °C.
Before use, attach the flying leads to the GK-404 by aligning the red circle on the silver “Lemo”
connector of the flying leads with the red line on the top of the GK-404 (Figure 4). Insert the
Lemo connector into the GK-404 until it locks into place.
Figure 4 - Lemo Connector to GK-404
Connect each of the clips on the leads to the matching colors 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 by the POS button, displayed as a letter 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 gauge in degrees Celsius.
Use the POS button to select position Band the MODE button to select Dg (digits). (Other
functions can be selected as described in the GK-404 Manual.)
The GK-404 will continue to take measurements and display readings until the unit is turned off,
either manually, or if enabled, by the Auto-Off timer. If no reading displays or the reading is
unstable, consult Section 11 for troubleshooting suggestions.
For further information, consult the GK-404 manual.

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3.2 GK-405 Readout Box
The GK-405 Vibrating Wire Readout is made up of two components: The Readout Unit,
consisting of a Windows Mobile handheld PC running the GK-405 Vibrating Wire Readout
Application; and the GK-405 Remote Module, which is housed in a weatherproof enclosure and
connects via a cable to the vibrating wire gauge to be measured. The two components
communicate wirelessly using Bluetooth®, a reliable digital communications protocol. The
Readout Unit can operate from the cradle of the Remote Module, or, if more convenient, can be
removed and operated up to 20 meters (65 feet) from the Remote Module.
3.2.1 Connecting Sensors with 10-pin Bulkhead Connectors Attached
Align the grooves on the sensor connector (male), with the appropriate connector on the
readout (female connector labeled senor or load cell). Push the connector into place, and
then twist the outer ring of the male connector until it locks into place.
3.2.2 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).
3.2.3 Operating the GK-405
Press the button labeled “POWER ON (BLUETOOTH)”. A blue light will begin
blinking, signifying that the Remote Module is waiting to connect to the handheld unit.
Launch the GK-405 VWRA program by tapping on “Start” from the handheld PC’s main
window, then “Programs” then the GK-405 VWRA icon. After a few seconds, the blue
light on the Remote Module should stop flashing and remain lit. The Live Readings
Window will be displayed on the handheld PC. Choose display mode “B”. Figure 5
shows a typical vibrating wire output in digits and thermistor output in degrees Celsius. If
no reading displays or the reading is unstable, see Section 11 for troubleshooting
suggestions. For further information, consult the GK-405 Instruction Manual.
Figure 5 - Live Readings – Raw Readings

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3.3 GK-403 Readout Box (Obsolete Model)
The GK-403 can store gauge readings and apply calibration factors to convert readings to
engineering units. The following instructions explain taking gauge measurements using Mode
“B”. Consult the GK-403 Instruction Manual for additional information.
3.3.1 Connecting Sensors with 10-pin Bulkhead Connectors Attached
Align the grooves on the sensor connector (male), with the appropriate connector on the
readout (female connector labeled senor or load cell). Push the connector into place, and
then twist the outer ring of the male connector until it locks into place.
3.3.2 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).
3.3.3 Operating the GK-403
1) Turn the display selector to position “B”.
2) Turn the unit on.
3) The readout will display the vibrating wire output in digits. The last digit may change
one or two digits while reading.
4) The thermistor reading will be displayed 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 11 for troubleshooting
suggestions.
The unit will automatically turn off after approximately two minutes to conserve power.
3.4 Measuring Temperatures
All vibrating wire transducers are equipped with a thermistor, which gives a varying resistance
output as the temperature changes. The white and green leads of the instrument cable are
normally connected to the internal thermistor.
The GK-403, GK-404, and GK-405 readout boxes will read the thermistor and display the
temperature in degrees C.
To read temperatures using an ohmmeter: Connect an ohmmeter to the green and white
thermistor leads coming from the displacement transducer. (Since the resistance changes with
temperature are large, the effect of cable resistance is usually insignificant. For long cables a
correction can be applied, equal to approximately 48.5Ωper km (14.7Ωper 1000 ft.) 20 °C.
Multiply these factors by two to account for both directions.) Look up the temperature for the
measured resistance in Appendix B, Table 2.

9
4. DATA REDUCTION
4.1 Calculation of Sensor Elevation
Readings can be used to calculate the elevation of the sensor and to plot them on a graph versus
time. The graph should also show the elevation of the fill above the sensor at the time of each
reading. A plot of temperature can also be included. For the standard 4650 settlement system,
using type 4500SV or 4500ALV transducers, the readings will get smaller as the sensors settle
relative to the reservoir.
For these sensors, the elevation (E) of the sensor is given by:
E = E0 – (R1 – R0) G + ∆ERES
Equation 1 - Elevation
Where;
E0is the sensor elevation at installation.
∆ERES is any change of the fluid level inside the reservoir sight glass.
(If the fluid level falls, ∆ERES is negative. If the fluid level rises, ∆ERES is positive.)
R0is the initial sensor reading.
R1is the subsequent sensor reading.
G is the calibration factor supplied with the sensor. (A typical calibration report supplied by the
factory is shown in Figure 6.)
For Example:
If;
E0 = 541.62 meters
R0 = 9030 digits
R1 = 8800 digits
G = -0.001765 meters/digit
∆ERES = –10 mm (i.e. the level of water in the reservoir sight tube is 10 mm lower than the level
measure at the time of the initial reading).
Then the new sensor elevation equals:
E = 541.62 – [(8800-9030) x -0.00175] + (–0.010)
E= 541.204 meters
In other words, there has been a settlement of 0.416 meters.

10
4.2 Correction for Settlement or Heave of the Reservoir Terminal
Periodic level surveys should be made of the elevation of the concrete pad on which the reservoir
terminal is located. Any measured settlement of the reservoir should be subtracted from the
calculated sensor elevations.
4.3 Corrections for Temperature
Temperature effects on liquid volume (liquid density) and on the expansion and contraction of
the liquid confines can be quite complex and in some ways self-canceling. Liquid lines in fills
are generally well insulated so that temperature effects tend to be insignificant. Systems exposed
to the atmosphere and to sunlight may suffer from rapidly changing temperatures at different
parts of the system causing significant fluctuation of the readings. In such cases, precautions may
be necessary to obtain readings at times of maximum temperature stability.
Temperature effects on the sensor can be corrected for but are usually quite insignificant
especially if the sensor is buried.
The elevation (ET) corrected for temperature is given by:
ET= E0 – [(R1 – R0) G + (T1– T0) K] +∆ERES
Equation 2 - Elevation, corrected for temperature
Where;
T0is the initial temperature.
T1is the current temperature.
K is the temperature correction factor included on the calibration report.
Please note: The calibration report shown in Figure 6 was developed using a simple manometer
and is good only over a range of three meters (ten feet) height differential between reservoir and
sensor. If this range is exceeded by the initial setup, or by large amounts of settlement, then there
are two options:
1) Continue to use the calibration report shown in Figure 6.
2) Use the second calibration report, supplied with the equipment, which was developed by
calibrating the pressure sensor over a wider range.

11
Figure 6 - Typical Calibration Report

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5. SPECIAL TOOLS AND APPARATUS REQUIRED FOR VARIOUS
TEST PROCEDURES
•GK-403, GK-404, or GK-405 Readout Box
•Assorted wrenches
•Nitrogen supply cylinder with regulator valve
•Pressure tanks filled with de-aired liquid (50% antifreeze solution made with distilled water
and containing dye)
•Vacuum pump and rubber connecting hoses with pinch clamps
•Motor generator (Gasoline powered)
•Auxiliary reservoir
•Miscellaneous connecting tubes and fitting
6. FLUSHING PROCEDURES
Periodic flushing of the liquid filled tubes may be required to remove air bubbles. A 300 meter
(1,000 foot) length of tubing requires 2.5 liters (0.67 gallons) of liquid. Tubes should always be
filled with de-aired liquid. Dye, added to the new flushing fluid, can be used to indicate when the
flushing is complete.
The best way to de-air a liquid is to use a Nold DeAerator (ask Geokon for more details). De-
aired liquid is also available from Geokon in two gallon or five-gallon pressure tanks specially
designed to prevent air from reaching the fluid. The liquid should also resist the growth of algae
and should not be liable to freeze in cold climates. The growth of algae can be prevented by
dissolving a crystal of copper sulfate in the liquid or by using commercial grade ethylene glycol
solutions, which also prevent freezing. The use of distilled water, rather than tap water, is
recommended. Figure 7 shows the apparatus recommended for flushing the tubes.
Figure 7 - Flushing Apparatus
Note that a bicycle pump can be used in place of the nitrogen cylinder.

13
1) Close the shut off valve at the base of the reservoir.
2) Disconnect one of the tubes and then reconnect it to the base of a filling tank that is filled
with de-aired liquid.
3) The second tube is disconnected and attached to the base of an auxiliary reservoir. (For tubes
longer than 200 meters (650 feet) it is recommended that a vacuum pump be attached to the
top of the auxiliary reservoir. This will speed up the flushing process.)
4) Connect a nitrogen cylinder with regulator to the top of the filling tank.
5) Start the vacuum pump running then open the valve at the bottom of the pressure tank.
6) Adjust the nitrogen pressure until the settlement sensor reads at its maximum range value on
the Readout Box. (See Section 3 for Readout instructions.) Be careful not to over range the
sensor by more than 20%. CAUTION! Do not allow the nitrogen pressure to exceed the
pressure rating marked on the outside of the filling tank (usually 100 psi (700 kPa).
Failure to observe this precaution could result in injury.
7) Continue flushing until all the old liquid has been removed. (As flushing proceeds, the
auxiliary reservoir may need to be emptied periodically.)
8) Store the flushed liquid in a container for later disposal. Do not allow any liquid to enter the
vacuum pump as this could ruin it.
9) When flushing is complete, reconnect the fluid lines to the base of the reservoir. Be careful
not to introduce air bubbles during this process.
7. PURGING THE VENT LINES
The vent line must remain open at all times; it connects the inside of the sensor to the space
above the reservoir. Any blockage of the vent line due to pinching, dirt, or moisture will cause
false readings that fluctuate and/or are sensitive to temperatures.
Blockages due to pinched tubes can be confirmed by applying a vacuum to the vent line and
observing the reading on the sensor. If the sensor does not respond the tube is blocked by dirt or
pinched, and this might be correctable if the blockage is accessible. Blockages due to moisture
and condensation can be purged using a vacuum pump to evacuate the vent line. As the vacuum
is applied watch for signs of water in the vent line. When the vacuum has stabilized, stop the
pump, disconnect the vent line, and quickly reattach either a desiccant chamber containing fresh
desiccant, or a cylinder of dry nitrogen. This ensures that the gas drawn back into the vent line is
dry. Make sure the vent line connection is open between the desiccant chamber (or vent line
manifold) and the top of the reservoir.

14
8. IN SITU CALIBRATION
A valuable feature of the Model 4650 settlement system is the ability to perform in situ
calibrations. This is done by connecting an auxiliary reservoir to one of the fluid lines as shown
in Figure 8.
Figure 8 - In Situ Calibration Apparatus
First close off the valve at the bottom of the reservoir, half-fill the auxiliary reservoir with the
same liquid used in the reservoir and connect it via a short length of tubing to one of the fluid
lines, being careful not to introduce air into the lines. Cap off the open fitting on the reservoir
connection and disconnect the vent line from the vent manifold. Raise and lower the auxiliary
reservoir by measured amounts using a scale to measure the elevation of the water level.
Read the sensor using a GK-403, GK-404, or GK-405 readout box. (See Section 3 for readout
instructions.) Record the readings after allowing sufficient time for the readings to stabilize
(usually requires around one to five minutes although it will be noted that the sensor responds
instantaneously to change of water elevation even where the liquid tubes are very long.) Record
the sensor readings at five or more different elevations, then, from the data calculate the
calibration factor and compare it with the factory generated value on the calibration report.
Remove the auxiliary reservoir and reconnect the fluid line to the base of the reservoir and the
vent line to the desiccant chamber or vent line manifold. Reopen the valve at the base of the
reservoir.