Geokon 4675LV Instruction Manual - User Manual

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Instruction Manual

Model 4675LV

Weir Monitor

No part of this instruction manual may be reproduced, by any 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.

(Doc Rev J, 10/23/17)

Warranty Statement

Geokon, Inc. 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, 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 the installation or use of the product. The buyer's sole remedy for any breach of this
agreement by Geokon, Inc. or any breach of any warranty by Geokon, Inc. shall not exceed the
purchase price paid by the purchaser to Geokon, Inc. 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, Inc. 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. INTRODUCTION .................................................................................................................................................. 1

2. INSTALLATION PROCEDURES ....................................................................................................................... 1

2.1

RELIMINARY

HECKS

........................................................................................................................................ 1

2.2

NSTALLATION

.................................................................................................................................................... 1

3. TAKING READINGS ............................................................................................................................................ 3

3.1

GK-404

EADOUT

...................................................................................................................................... 3

3.1.1 Operating the GK-404 ................................................................................................................................ 3

3.2

GK-405

EADOUT

...................................................................................................................................... 4

3.2.1 Connecting Sensors .................................................................................................................................... 4

3.2.2 Operating the GK-405 ................................................................................................................................ 4

3.3

GK-403

EADOUT

BSOLETE

ODEL

) ..................................................................................................... 5

3.3.1 Connecting Sensors to the GK-403 ............................................................................................................ 5

3.3.2 Operating the GK-403 ................................................................................................................................ 5

3.4

EASURING

EMPERATURES

.............................................................................................................................. 5

4. DATA REDUCTION .............................................................................................................................................. 6

4.1

ETERMINATION OF

ATER

LEVATION

............................................................................................................ 6

4.2

ORRECTIONS FOR

EMPERATURE

HANGES

..................................................................................................... 8

4.3

ENSITY AND

OMPRESSIBILITY

........................................................................................................................ 8

5. MAINTENANCE .................................................................................................................................................... 9

5.1

OISTURE

RAP

................................................................................................................................................. 9

5.2

EIGHT

AINTENANCE

...................................................................................................................................... 9

5.3

ENSOR

............................................................................................................................................................... 9

6. TROUBLE SHOOTING ........................................................................................................................................ 9

APPENDIX A. SPECIFICATIONS .........................................................................................................................10

APPENDIX B. THERMISTOR TEMPERATURE DERIVATION .....................................................................11

APPENDIX C. SWAGELOK TUBE FITTING INSTRUCTIONS ......................................................................12

C.1

NSTALLATION

...................................................................................................................................................12

C.2

EASSEMBLY

NSTRUCTIONS

............................................................................................................................13

FIGURES, TABLES AND EQUATIONS

IGURE

TILLING

ELL

UPPORTS

.......................................................................................................................... 2

IGURE

EMO

ONNECTOR TO

GK-404 ................................................................................................................... 3

IGURE

IVE

EADINGS

–

EADINGS

............................................................................................................... 4

IGURE

YPICAL

ALIBRATION

HEET

..................................................................................................................... 7

IGURE

ENSITY OF WATER AS A FUNCTION OF TEMPERATURE AND PRESSURE INTENSITY

...................................... 8

IGURE

UBE

NSERTION

.........................................................................................................................................12

IGURE

AKE A

ARK AT

O’

CLOCK

................................................................................................................12

IGURE

IGHTEN

NE AND

-Q

UARTER

URNS

.................................................................................................12

IGURE

ARKS FOR

EASSEMBLY

..........................................................................................................................13

IGURE

ERRULES

EATED

GAINST

ITTING

ODY

.............................................................................................13

IGURE

IGHTEN

LIGHTLY

...........................................................................................................................13

ABLE

HERMISTOR

ESISTANCE VERSUS

EMPERATURE

......................................................................................11

QUATION

HANGE IN

ATER

EIGHT

.................................................................................................................... 6

QUATION

ORRECTION FOR

EMPERATURE

ENSITY

HANGES

............................................................................ 8

QUATION

ESISTANCE TO

EMPERATURE

.............................................................................................................11

1. INTRODUCTION

The Geokon Model 4675LV Weir Monitor is designed for the measurement of water levels in
streams, weirs, flumes, etc., where accurate measurements of very small water level changes are
required. The unit consists of a vibrating wire from which is suspended a hanging cylindrical
weight partially submerged in the water. As the water level rises and falls, the buoyancy forces
acting on the weight change causing changes in the tension and vibrational frequency in the
vibrating wire. Level changes of as little as .001 inches can be measured. Ranges of up to 10 feet
are available.

2. INSTALLATION PROCEDURES

2.1 Preliminary Checks

Before installing the weight cylinder, remove the orange colored spacer that lies between
the base of the sensor and the nut on the hook assembly.

(This releases the tension in the

sensor wire –put there as a safety precaution to protect the sensor from damage during shipment.)

The gage and weight assembly can now be checked out on site by connecting the sensor to the
readout system and measuring the output of the sensor with the weight hanging from it in air.
The readings should coincide within about 200 digits of the factory reading in air shown on the
calibration sheet. (See Section 3 for readout instructions. Be sure that the sensor is held firmly
and the system is allowed to stabilize (no swinging of the weight). Detach the weight after this
preliminary check.

Always handle with great care to prevent breakage

2.2 Installation

If the 4675LV is used in a weir box, a Stilling Well is required. The Stilling Well is provided by
Geokon, in the form of a slotted, three or four inch PVC pipe. This Stilling Well must be
installed in a

vertically plumb

position, in an area where there is little turbulence, and

positioned in such a way that

the bottom of the weight is slightly lower than the tip of the V

notch.

It is important that the well be vertical, because any friction from the weight rubbing

along the well will influence the sensor output

The installation is made by using two pipe straps to hold the stilling well in place. Two spacer
bars are provided to hold the stilling well away from the wall so that the stilling well cap can be
removed and replaced as necessary. For concrete weir boxes, four Rawl plugs are provided.
Mark out the position for four bolt holes, (see Figure 1), and drill a 1/2 inch (12 mm) diameter
hole two inches (50 mm) deep at each location. (The spacer bar can be used to help locate the
hole spacing properly). A 3/8 Rawl plug (four provided) is installed in each hole, using the
installation tool provided. The Rawl plug is first placed in the hole and tapped flush with the
surface. Then place the installation tool inside the Rawl plug and set the anchor by means of
several sharp hammer blows.

The PVC slotted tubing has a bottom plug at its lower end, which can now be cemented in place
using PVC cement. (It is left loose in case the PVC pipe needs to be shortened a little due to
space limitations). Use the four 3/8-16 bolts provided to bolt the stilling well to the wall of the
weir box using the pipe strap and spacer bars.

Figure 1 - Stilling Well Supports

Check that the sensor is reading then push it inside the Swagelok fitting in the pipe cap and
tighten the According to the instructions in Appendix C. Leave about one inch of the sensor
protruding from the Swagelok. Carefully attach the weight to the eyebolt on the base of the
sensor and lower the assembly into the stilling well until the pipe cap sits firmly on top of the
pipe.

The yellow vented readout cable can now be extended to a local readout location where an
optional terminal box can be used to enclose the end of the yellow vented cable, as well as the
vent line moisture trap. If the readout location is remote from the weir location then a blue
unvented cable can be used between the terminal box containing the moisture trap and the
readout location.

The seal screw on the bottom of the desiccant chamber must be kept open

while the Weir Monitor is in operation.

The proper color for the desiccant is blue. If the color

is pink then fresh desiccant is required.

3. TAKING 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 gages and transducers, and is capable of displaying the
reading in either digits, frequ

ency (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.

3.1.1 Operating the GK-404

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
2). Insert the Lemo connector into the GK-404 until it locks into place.

Figure 2 - 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) of the GK-404 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 gage in degrees Celsius.

Use the

POS

button to select position

and the

MODE

button to select

(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. For further details
information the GK-404 manual.

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 gage 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 from the Remote Module.

3.2.1 Connecting Sensors

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.

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).

3.2.2 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 3 shows a typical vibrating wire output in digits and thermistor output in degrees
Celsius.

Figure 3 - Live Readings – Raw Readings

For further information, consult the GK-405 Instruction Manual.

3.3 GK-403 Readout Box (Obsolete Model)

The GK-403 can store gage readings and apply calibration factors to convert readings to
engineering units. The following instructions explain taking gage measurements using Mode "B"
(similar to the GK-401 switch positions "B").

3.3.1 Connecting Sensors to the GK-403

Connecting Sensors with 10-pin Bulkhead Connectors Attached:

Connecting Sensors with Bare Leads:

3.3.2 Operating the GK-403

Turn the display selector to position "B".

Turn the unit on.

The readout will display the vibrating wire output in digits. The last digit may change
one or two digits while reading.

The thermistor reading will be displayed above the gage reading in degrees
centigrade.

Press the "Store" button to record the value displayed.

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 liquid level sensors are equipped with a thermistor that 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 strain gage.
(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 14.7 ohms per
one thousand feet. Multiply this factor by two to account for both directions.)

Look up the temperature for the measured resistance in Appendix B, Table 1.

4. DATA REDUCTION

4.1 Determination of Water Elevation

Each type of weir, depending on its type, shape, and size has an equation relating the volume of
fluid passing over it to the height of water, H, passing over the weir.
The change in height of the water is directly proportioned to the change in output of the
transducer. The following formula applies for the determination of the change in water height:

ΔH = (R

– R

) G

Equation 1 - Change in Water Height

Where;

is the height of water above the tip of the weir.

is the initial reading.

is the subsequent reading.

is the calibration factor in the height units /digit shown on the calibration sheet. (See Figure 4

for an example of a typical calibration sheet.)

At the time that the initial reading (R

) is taken, it is necessary to measure accurately as possible

the difference in elevation between the surface of the water in the weir box and the tip of the
weir. If the weir plate is graduated, simply record the initial water level as indicated, call this
difference in elevation

Then;
H = (R

– R

) G +

inches or mm

Alternatively, from the initial reading (

) taken when the measured water height is

inches, it

is possible, using the gage factor (

), to calculate the reading equivalent to the water level at the

tip of the V notch (

For instance:

If;
R

= 6500

= 5.2 inches

G= - 0.001981 inches

Then;
R

= 6500 + 5.2/0.001981= 9125 and H = G(R

-9125)

Another method, if possible, is to adjust the height of water so that water just trickles over the V
notch tip, and then take the R

reading.

Figure 4 - Typical Calibration Sheet

4.2 Corrections for Temperature Changes

The vibrating wire sensor itself is insensitive to temperature changes within the normal operating
range. The system, however, is not entirely unaffected by changes in water temperature which
influence the density and therefore, the buoyancy of the fluid. The influence is relatively minor
and can be accounted for to some degree by measuring the water temperature and making
density corrections. Alternatively, two sensors can be used, one of which is completely
submerged at all times, and whose output can be used to make corrections for the other sensor.
This technique is not fool proof either, since the water may have temperature gradients that the
submerged sensor may or may not intersect. A temperature/density curve for water is shown in
Figure 5. As can be seen from the data the density of the water changes very little in the normal
operating range of the sensor. The following equation is used to correct for temperature/density
changes:

∆

H = (R

) G /(1-0.0002T

) - (R

) G /(1- 0.0002T

)

Equation 2 - Correction for Temperature/Density Changes

Where;

is the height of water above the tip of the weir.

is the initial reading.

is the subsequent reading.

is the initial water temperature in

is the current water temperature in

is the calibration factor in the height units /digit shown on the calibration sheet. (See Figure 4

for an example of a typical calibration sheet.)

4.3 Density and Compressibility

Density is defined as the mass per unit volume, and it depends upon the temperature and pressure
intensity. The density of pure water is given in Figure 5 below.

Figure 5 - Density of water as a function of temperature and pressure intensity

(Figure 5 used with permission from

Fluid Mechanics for Hydraulic Engineers,

by Hunter

5. MAINTENANCE

5.1 Moisture Trap

The vibrating wire sensor has a vent tube to prevent loading on the sensor due to changes in
atmosphere pressure, and the moisture trap on the vent line requires periodic changing of the
desiccant capsules. The frequency of this is dependent on weather conditions, but three to six
months is a normal period. The seal screw on the moisture trap must be left open when the weir
monitor is in operation.

5.2 Weight Maintenance

Since the weight is assumed to be of constant mass, it is important that it be kept clean and free
of encrustation, algal growth, etc. Periodic observation should be made and this can coincide
with the moisture trap maintenance.

5.3 Sensor

Maintenance of the sensor itself is confined to periodic checks of cable connections and
maintenance of terminals. The transducers themselves cannot be opened for inspection.

6. TROUBLE SHOOTING

Should difficulties arise, consult the following list of problems and possible solutions. For
additional troubleshooting and support, contact Geokon.

Symptom: Thermistor resistance is too high



Likely, there is an open circuit. Check all connections, terminals, and plugs. If a cut is
located in the cable, splice according to recommended procedures.

Symptom: Thermistor resistance is too low



A short is likely. Check all connections, terminals, and plugs. If a short is located in the
cable, splice according to recommended procedures.



Water may have penetrated the interior of the transducer. There is no remedial action.

Symptom: Transducer reading unstable



Make sure the shield drain wire is connected to the blue clip on the flying leads. (Green for
the GK-401.)



Isolate the readout from the ground by placing it on a piece of wood or other insulator.



Check for sources of nearby electrical noise such as motors, generators, antennas, or
electrical cables. Move the transducer cable away from these sources if possible. Contact the
factory for available filtering and shielding equipment.

APPENDIX A. SPECIFICATIONS

Model No.

4675LV

Standard Ranges

150, 300, 600, 1500 mm

Accuracy

0.1% F.S.

Temperature Range

-30 to +80

Frequency Range

1400-3500 Hz

Materials:

Sensor and Weight:

Stainless steel

Sitting Well:

PVC standard, stainless steel (optional)

Cable

Four Conductor, 22 gage PVC jacket

Sensor

Diameter: 1.00”

Length: 8.5”

Other ranges available on request

Accuracy achieved by using a polynomial expression rather than a linear coefficient

Using antifreeze solution can extend the range below 0 °C. The system requires calibration with

the solution being used.

APPENDIX B. THERMISTOR TEMPERATURE DERIVATION

Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3
Resistance to Temperature Equation:

A+B

(

LnR

)

+C(LnR)

-273.2

Equation 3 - Resistance to Temperature

Where;

Temperature in

LnR

Natural Log of Thermistor Resistance

1.4051

10-3

2.369

10-4

1.019

10-7

Note: Coefficients calculated over the

−

50 to +150

C. span.

Ohms

Temp

Ohms

Temp

Ohms

Temp

Ohms

Temp

Ohms

Temp

201.1K

-50

16.60K

-10

2417

525.4

153.2

110

187.3K

-49

15.72K

-9

2317

507.8

149.0

111

174.5K

-48

14.90K

-8

2221

490.9

145.0

112

162.7K

-47

14.12K

-7

2130

474.7

141.1

113

151.7K

-46

13.39K

-6

2042

459.0

137.2

114

141.6K

-45

12.70K

-5

1959

444.0

133.6

115

132.2K

-44

12.05K

-4

1880

429.5

130.0

116

123.5K

-43

11.44K

-3

1805

415.6

126.5

117

115.4K

-42

10.86K

-2

1733

402.2

123.2

118

107.9K

-41

10.31K

-1

1664

389.3

119.9

119

101.0K

-40

9796

1598

376.9

116.8

120

94.48K

-39

9310

1535

364.9

113.8

121

88.46K

-38

8851

1475

353.4

110.8

122

82.87K

-37

8417

1418

342.2

107.9

123

77.66K

-36

8006

1363

331.5

105.2

124

72.81K

-35

7618

1310

321.2

102.5

125

68.30K

-34

7252

1260

311.3

99.9

126

64.09K

-33

6905

1212

301.7

97.3

127

60.17K

-32

6576

1167

292.4

94.9

128

56.51K

-31

6265

1123

283.5

92.5

129

53.10K

-30

5971

1081

274.9

90.2

130

49.91K

-29

5692

1040

266.6

87.9

131

46.94K

-28

5427

1002

258.6

85.7

132

44.16K

-27

5177

965.0

250.9

83.6

133

41.56K

-26

4939

929.6

243.4

81.6

134

39.13K

-25

4714

895.8

236.2

79.6

135

36.86K

-24

4500

863.3

229.3

77.6

136

34.73K

-23

4297

832.2

222.6

75.8

137

32.74K

-22

4105

802.3

216.1

73.9

138

30.87K

-21

3922

773.7

209.8

72.2

139

29.13K

-20

3748

746.3

203.8

100

70.4

140

27.49K

-19

3583

719.9

197.9

101

68.8

141

25.95K

-18

3426

694.7

192.2

102

67.1

142

24.51K

-17

3277

670.4

186.8

103

65.5

143

23.16K

-16

3135

647.1

181.5

104

64.0

144

21.89K

-15

3000

624.7

176.4

105

62.5

145

20.70K

-14

2872

603.3

171.4

106

61.1

146

19.58K

-13

2750

582.6

166.7

107

59.6

147

18.52K

-12

2633

562.8

162.0

108

58.3

148

17.53K

-11

2523

543.7

157.6

109

56.8

149

Table 1 - Thermistor Resistance versus Temperature

55.6

150

APPENDIX C. SWAGELOK TUBE FITTING INSTRUCTIONS

These instructions apply to

one inch (25 mm) and smaller fittings

C.1 Installation

Fully insert the tube into the fitting until it bumps against the shoulder.

Figure 6 - Tube Insertion

Rotate the nut until it is finger-tight. (For high-pressure applications as well as high-safety-
factor systems, further tighten the nut until the tube will not turn by hand or move axially in
the fitting.)

Mark the nut at the six o’clock position.

Figure 7 - Make a Mark at Six O’clock

While holding the fitting body steady, tighten the nut one and one-quarter turns until the
mark is at the nine o’clock position. (Note: For 1/16”, 1/8”, 3/16”, and 2, 3, and 4 mm
fittings, tighten the nut three-quarters of a turn until the mark is at the three o’clock position.)

Figure 8 - Tighten One and One-Quarter Turns

C.2 Reassembly Instructions

Swagelok tube fittings may be disassembled and reassembled many times.

Warning! Always depressurize the system before disassembling a Swagelok tube fitting.

Prior to disassembly, mark the tube at the back of the nut, then make a line along the nut and
fitting body flats.

These marks will be used during reassembly to ensure the nut is returned to

its current position.

Figure 9 - Marks for Reassembly

Disassemble the fitting.

Inspect the ferrules for damage and replace if necessary.

If the ferrules are replaced the

connector should be treated as a new assembly. Refer to the section above for
installation instructions.

Reassemble the fitting by inserting the tube with preswaged ferrules into the fitting until the
front ferrule seats against the fitting body.

Figure 10 - Ferrules Seated Against Fitting Body

While holding the fitting body steady, rotate the nut with a wrench to the previous position as
indicated by the marks on the tube and the connector. At this point, there will be a significant
increase in resistance.

Tighten the nut slightly.

Figure 11 - Tighten Nut Slightly

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