Geokon 6165 User manual

Installation Instructions
Model 6165
MEMS Tilt Beam
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.
Copyright © 2010-2018 by Geokon, Inc.
(Rev E, 07/17/18)

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 ....................................................................................................................................................2
2.1 PRELIMINARY TESTS............................................................................................................................................2
2.2 ATTACHING MOUNTING BRACKETS.....................................................................................................................2
2.3 MOUNTING THE BEAM.........................................................................................................................................3
3. TAKING READINGS.............................................................................................................................................5
3.1 INITIAL READINGS...............................................................................................................................................5
3.2 DATALOGGERS ....................................................................................................................................................5
3.3 RB-500 READOUT BOX .......................................................................................................................................5
3.4 MEASURING TEMPERATURE ................................................................................................................................6
4. DATA REDUCTION ..............................................................................................................................................7
4.1 TILT CALCULATION .............................................................................................................................................7
4.2 DISPLACEMENT CALCULATION............................................................................................................................7
4.3 TEMPERATURE CORRECTION...............................................................................................................................8
4.4 ENVIRONMENTAL FACTORS.................................................................................................................................8
5. TROUBLESHOOTING..........................................................................................................................................9
APPENDIX A. SPECIFICATIONS.........................................................................................................................10
A.1 MODEL 6165 MEMS TILT BEAM......................................................................................................................10
A.2 THERMISTOR (SEE APPENDIX BALSO)..............................................................................................................10
APPENDIX B. THERMISTOR TEMPERATURE DERIVATION.....................................................................11
APPENDIX C. SAMPLE CALIBRATION REPORT...........................................................................................12
APPENDIX D. PROGRAMMING THE MEMS TILT BEAM WITH CRBASIC.............................................13
D.1 DESCRIPTION ....................................................................................................................................................13
D.2 SAMPLE PROGRAM............................................................................................................................................13

FIGURES
FIGURE 1-MODEL 6165 MEMS TILT BEAM................................................................................................................. 1
FIGURE 2-BRACKET HARDWARE ................................................................................................................................. 2
FIGURE 3-BRACKETS ATTACHED TO BEAM ................................................................................................................. 3
FIGURE 4-MOUNTING BRACKET ORIENTATION ........................................................................................................... 3
FIGURE 5-MOUNTING HARDWARE............................................................................................................................... 4
FIGURE 6-SAMPLE MODEL 6165 CALIBRATION REPORT.............................................................................................12
TABLES
TABLE 1-03-250V0 CABLE WIRING............................................................................................................................. 5
TABLE 2-MODEL 6165 MEMS TILT BEAM SENSOR SPECIFICATIONS .........................................................................10
TABLE 3-THERMISTOR RESISTANCE VERSUS TEMPERATURE .....................................................................................11
EQUATIONS
EQUATION 1-INCLINATION........................................................................................................................................... 7
EQUATION 2-CALCULATED TILT.................................................................................................................................. 7
EQUATION 3-CALCULATED DISPLACEMENT ................................................................................................................ 7
EQUATION 4-TEMPERATURE CORRECTION -TILT ........................................................................................................ 8
EQUATION 5-TEMPERATURE CORRECTION -DISPLACEMENT....................................................................................... 8
EQUATION 6-RESISTANCE TO TEMPERATURE .............................................................................................................11

1
1. INTRODUCTION
Geokon’s Model 6165 MEMS Tilt Beams are designed to be attached to structures, either
vertically or horizontally, to measure any tilting or differential settlements that may occur. The
tilt beams can be coupled together, in long horizontal strings, to measure differential settlement
along embankments, railroad tracks, pipelines, tunnels, etc. They can also be used in vertical
strings to measure the horizontal deformation of retaining walls, sheet piling, etc.
Each tilt beam contains a Micro-Electro-Mechanical-System (MEMS) sensor, which offers high
sensitivity and accuracy over a range of ±15 degrees. MEMS tilt sensors have very good long-
term stability, are virtually immune to shock loading, and have very low thermal coefficients.
They are readily adaptable to automation and remote monitoring for profiling in real-time. The
included signal conditioning yields a sensor output of ±3 volts at ±10 degrees and is designed to
drive long cables without output signal degradation.
The MEMS sensor is mounted inside a fiberglass, aluminum, or anodized aluminum channel
equipped with lugs for mounting to the structure under study. The beams are bolted to the
structure using the supplied hardware, which includes two 3/8" expansion anchors. A thermistor
mounted inside the sensor housing permits the measurement of temperatures. Readout of the tilt
beams is accomplished by using a Geokon Model RB-500 Readout, or 8600 Series Datalogger.
Figure 1 - Model 6165 MEMS Tilt Beam

2
2. INSTALLATION
2.1 Preliminary Tests
Prior to installation, each tilt beam should be checked for proper operation by completing the
following:
1) Connect the beam to a readout or datalogger. (See Section 3 for readout and datalogger
instructions.)
2) Depending upon which version of the tilt beam was purchased, hold the beam in a strictly
horizontal or vertical position. The beam must be held in a steady position while taking
readings. The observed reading should be close to the factory zero reading provided on the
calibration report. (Note that the RB-500 Readout Box uses a 2:1 voltage divider to halve
the full-scale output of the MEMS sensor, which is ±4 volts. This is done so that the ±2
volt DVM in the RB-500 readout box can display the full output range of the MEMS
sensor.)
3) At one end of the beam there is a label that shows the sign of the change in readout voltage
when that end of the beam is tilted in the direction shown. Tilts in a positive direction (+)
should yield increasing readings. Tilts in a negative direction (-) should yield decreasing
readings. The temperature indicated on the readout should be close to ambient.
4) Repeat this process with the remaining beams.
Should any of these preliminary tests fail, see Section 5 for troubleshooting.
2.2 Attaching Mounting Brackets
Each beam is supplied with mounting brackets and associated hardware (Figure 2). To mount the
brackets to the beam: Slide the external tooth lock washers (D) onto the bolts (C), followed by
the flat washers (E). Use the bolts to attach the mounting brackets to the ends of the beam. Figure
3 shows the completed assembly.
Figure 2 - Bracket Hardware

3
Figure 3 - Brackets Attached to Beam
Make sure the mounting brackets are orientated so that when the beam is mounted, the front of
the beam will be facing out, as shown in Figure 4.
Figure 4 - Mounting Bracket Orientation
2.3 Mounting the Beam
1) Place the beam in the desired location.
2) Use a spirit level to make sure the beam is as close to a truly vertical or horizontal position as
possible, depending upon the type of beam purchased.
3) Using the beam as a template, mark the locations of the holes in the mounting brackets on the
mounting surface. The marks should be as close as possible to being in line on a horizontal or
vertical plane.
4) Using a masonry drill (or other suitable equipment), drill two 12 mm (1/2") diameter holes,
approximately 40 mm (1.6") deep at the marked locations.
5) Clean the holes thoroughly. (Blow them out with compressed air if possible.)
6) Insert the expansion anchors into the holes, with the slotted end down.
7) Insert the provided setting tool, small end first, into the anchor. Expand the anchor by hitting
the large end of the setting tool with several sharp hammer blows.
8) Thread the supplied 3/8-16 anchor rod into the anchor. Thread-locking cement can be used to
ensure the hardware remains secure.

4
9) Attach the beam to the mounting surface by arranging the mounting hardware as shown in
Figure 5. Use thread locking cement if desired.
Figure 5 - Mounting Hardware
10)The beam must be level along the axis of the beam, as well as the perpendicular axis. This is
to avoid any off-axis errors which can occur if the MEMS sensor is rotated axially too far
away from a true horizontal or vertical position. The spherical washers allow the beam to be
rotated in respect to the anchor bolt, thus adjustments can be made to avoid this type of error.
For vertical tilt beams, the axis of tilt can be either in the plane of the wall or perpendicular to
the wall. The direction is selectable by slackening the bolts holding the mounting brackets to
the ends of the beam and turning it 90 degrees.

5
3. TAKING READINGS
3.1 Initial Readings
The displayed output of the initial zero readings should be close to the factory zero reading
provided on the calibration report. The sensor output at ±15 degrees is ±4 volts.
Note that the RB-500 Readout Box uses a 2:1 voltage divider to halve the full-scale output
of the MEMS sensor, which is ±4 volts. This is done so that the ±2 volt DVM in the RB-500
readout box can display the full output range of the MEMS sensor.
3.2 Dataloggers
In most cases, the tilt beam will be monitored continuously and automatically using a
Datalogger. Connections to Geokon 8600 series dataloggers, which uses Campbell Scientific
CR6 MCU are shown in Table 1 below. For further information, consult the 8600 Series
Instruction Manual.
03-250V0 Cable Connector Pin Designation Function
Red
A
12VDC
Red’s Black
B
Ground
White
C
A Out Diff +
White’s Black
D
A Out Diff -
Bare
E
Shield
Green
J
Thermistor
Green’s Black
K
Thermistor
Table 1 - 03-250V0 Cable Wiring
3.3 RB-500 Readout Box
The RB-500 readout box is designed to display readings for manually transcribing into a field
book; it has no storage capabilities. This method is useful for reading systems that do not require
continuous monitoring. The RB-500 readout box is also useful during initial installations and for
setting up Datalogger systems.
Connect the leads of the beam to the RB-500 as shown on the readout overlay.
Note that the RB-500 Readout Box uses a 2:1 voltage divider to halve the full-scale output
of the MEMS sensor, which is ±4 volts. This is done so that the ±2 volt DVM in the RB-500
readout box can display the full output range of the MEMS sensor.
For further information, consult the RB-500 Instruction Manual.

6
3.4 Measuring Temperature
All tilt beams are equipped with a thermistor, which gives a varying resistance output as the
temperature changes. Although the temperature dependence of the MEMS tilt beam is very
small, and usually does not require compensation, it sometimes happens that temperature effects
can cause real changes of tilt; therefore, each MEMS tilt sensor is equipped with a thermistor for
reading temperature. This enables temperature-induced changes in tilt to be distinguished from
tilts due to other sources. See Section 4.3)
The RB-500 will not read temperatures; a separate digital ohmmeter is required. (A Geokon
GK-404 or GK-405 readout box can also be used; they have the ability to read the thermistor and
display the temperature in degrees C.)
To read temperatures using an ohmmeter:
1) Connect an ohmmeter to the green and green’s black conductors of the tilt beam. 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 14.7 Ω per
one thousand feet (48.5Ω per km). Multiply this factor by two to account for both directions.
2) Look up the temperature for the measured resistance in Appendix B, Table 3.

7
4. DATA REDUCTION
4.1 Tilt Calculation
The output of the MEMS Sensor is proportional to the sine of the angle of inclination from the
zero position. For the 15 degree MEMS sensor the full-scale output is approximately four volts.
The reading (R) in volts displayed on the RB-500 readout box, and the inclination, (θ) is given
by the equation:
θ= Gtilt (R1-Rzero) degrees
Equation 1 - Inclination
Where;
Ris the current reading in volts.
Rzero is the reading at θ= zero.
Gtilt is the Gage Factor shown on the suppled calibration report (A typical 6165 calibration report
is shown in Appendix C.)
Note that for measurements of tilt, i.e., changes of inclination, where R0 is the initial reading and
R1 is a subsequent reading, the small zero reading (Rzero) at zero inclination cancels out, so that:
Calculated Tilt (T) = Gtilt(R1-R0) degrees
Equation 2 - Calculated Tilt
4.2 Displacement Calculation
To calculate the vertical or horizontal displacement (D) of one end of the beam relative to the
other use the equation:
Calculated Displacement (D) = GsinθL(R1-R0) mm(inches)
Equation 3 - Calculated Displacement
Where;
L is length of the beam in mm or inches
Gsinθ is the calibration factor in sinθ/volt as shown on the calibration report.

8
4.3 Temperature Correction
The Model 6165 MEMS Tilt Beam sensor has negligible temperature sensitivity equal to one arc
second per degree C or 0.0003 volts/ degree C.
Tilt corrected for temperature = Gtilt[(R1-R0) - 0.0003(T1-T0)] degrees
Equation 4 - Temperature Correction - Tilt
The corresponding correction for displacement is:
Displacement corrected for temperature = GsinθL[(R1-R0) - 0.0003(T1-T0)] mm(inches)
Equation 5 - Temperature Correction - Displacement
The structure being monitored and the tilt beam are both affected by temperature to some degree.
An important point to note is that sudden changes in temperature will cause both the structure
and the tilt beam to undergo transitory physical changes, which will show up in the readings. A
system temperature correction factor can be calculated by taking readings of tilt and temperature
over a short period of time and correlating the two. Alternatively, efforts can be made to obtain
readings when the instrument and structure are at thermal equilibrium. The best time for this
tends to be in the late evening or early morning hours. For best results, the Tilt Beam should
be shielded from direct sunlight.
4.4 Environmental Factors
Since the purpose of the tilt beam installation is to monitor site conditions, factors that may
affect these conditions should be observed and recorded. Seemingly minor effects may have a
real influence on the behavior of the structure being monitored and may give an early indication
of potential problems. Some of these factors include, but are not limited to, blasting, rainfall,
tidal or reservoir levels, excavation and fill levels and sequences, traffic, temperature and
barometric changes, changes in personnel, nearby construction activities, seasonal changes, etc.

9
5. TROUBLESHOOTING
Maintenance and troubleshooting of Model 6165 Tilt Beams are confined to periodic checks of
the cable connections. The sensors are sealed and there are no user serviceable parts. Consult the
following list of problems and possible solutions should difficulties arise. Consult the factory for
additional troubleshooting help.
Symptom: Tilt Sensor Readings are Unstable
Is there a source of electrical noise nearby? Most probable sources of electrical noise are
motors, generators, 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 tilt sensor? If not, the readout may have a low battery or
be malfunctioning.
Symptom: Tilt Sensor Fails to Read
Is the cable cut or crushed? If the approximate temperature is known, the resistance of the
thermistor leads can be estimated and used as a cable check. Connect an ohmmeter to the
green and green’s black conductors of the tilt beam. 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 14.7 Ω per one thousand feet (48.5Ω per
km). Multiply this factor by two to account for both directions. If the resistance reads very
high or infinite (megohms), a cut wire must be suspected. If the resistance reads very low
(<20Ω), a short in the cable is likely.
Does the readout or datalogger work with another tilt sensor? If not, the readout or datalogger
may be malfunctioning.
Symptom: Thermistor resistance is too high
It is likely that there is an open circuit. Check all connections, terminals, and plugs. If a cut is
located in the cable, contact Geokon for splicing information.
Symptom: Thermistor resistance is too low
It is likely that there is a short. Check all connections, terminals, and plugs. If a short is
located in the cable, contact Geokon for splicing information.
Water may have penetrated the interior of the beam. There is no remedial action.

10
APPENDIX A. SPECIFICATIONS
A.1 Model 6165 MEMS Tilt Beam
Range:
±15°
FS Output:
±Four Volts
Resolution:1
±Two arc seconds, (±0.01 mm/meter)
Accuracy:
0.1% F.S.
Linearity:
0.2% F.S. (±5 degree range),
0.5% F.S. (±10 degree range). ±1.5% F.S.
Thermal Zero Shift:
0.0003 volt/°C rise
Operating
Temperature:
-20 to +70° C
-40 to 200° F
Power Requirements2:
+12V (nom) @ 30mA
Beam Dimensions:
1.5", 38 mm square cross section
Length:
Variable
Weight:
1.5 lb. (0.7 kg)
Materials:
Aluminum
Electrical Cable:
Three twisted pair (Six conductor) 24 AWG for uniaxial
Foil shield, PVC jacket, nominal OD = 6.3 mm
Table 2 - Model 6165 MEMS Tilt Beam Sensor Specifications
Notes:
1Depends on readout equipment. For best results requires a 4.5 digit digital voltmeter.
2Voltages in excess of 18V will damage the circuitry and are to be avoided
A.2 Thermistor (See Appendix B also)
Range: -80 to +150 °C
Accuracy: ±0.5 °C

11
APPENDIX B. THERMISTOR TEMPERATURE DERIVATION
Thermistor Type: YSI 44005, Dale #1C3001-B3, Alpha #13A3001-B3
Resistance to Temperature Equation:
T= 1
A+B(LnR)+C(LnR)3-273.2
Equation 6 - Resistance to Temperature
Where;
T=Temperature in °C.
LnR =Natural Log of Thermistor Resistance
A=1.4051 ×10-3
B=2.369 ×10-4
C=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
+30
525.4
+70
153.2
+110
187.3K
-49
15.72K
-9
2317
31
507.8
71
149.0
111
174.5K
-48
14.90K
-8
2221
32
490.9
72
145.0
112
162.7K
-47
14.12K
-7
2130
33
474.7
73
141.1
113
151.7K
-46
13.39K
-6
2042
34
459.0
74
137.2
114
141.6K
-45
12.70K
-5
1959
35
444.0
75
133.6
115
132.2K
-44
12.05K
-4
1880
36
429.5
76
130.0
116
123.5K
-43
11.44K
-3
1805
37
415.6
77
126.5
117
115.4K
-42
10.86K
-2
1733
38
402.2
78
123.2
118
107.9K
-41
10.31K
-1
1664
39
389.3
79
119.9
119
101.0K
-40
9796
0
1598
40
376.9
80
116.8
120
94.48K
-39
9310
+1
1535
41
364.9
81
113.8
121
88.46K
-38
8851
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
1040
51
266.6
91
87.9
131
46.94K
-28
5427
12
1002
52
258.6
92
85.7
132
44.16K
-27
5177
13
965.0
53
250.9
93
83.6
133
41.56K
-26
4939
14
929.6
54
243.4
94
81.6
134
39.13K
-25
4714
15
895.8
55
236.2
95
79.6
135
36.86K
-24
4500
16
863.3
56
229.3
96
77.6
136
34.73K
-23
4297
17
832.2
57
222.6
97
75.8
137
32.74K
-22
4105
18
802.3
58
216.1
98
73.9
138
30.87K
-21
3922
19
773.7
59
209.8
99
72.2
139
29.13K
-20
3748
20
746.3
60
203.8
100
70.4
140
27.49K
-19
3583
21
719.9
61
197.9
101
68.8
141
25.95K
-18
3426
22
694.7
62
192.2
102
67.1
142
24.51K
-17
3277
23
670.4
63
186.8
103
65.5
143
23.16K
-16
3135
24
647.1
64
181.5
104
64.0
144
21.89K
-15
3000
25
624.7
65
176.4
105
62.5
145
20.70K
-14
2872
26
603.3
66
171.4
106
61.1
146
19.58K
-13
2750
27
582.6
67
166.7
107
59.6
147
18.52K
-12
2633
28
562.8
68
162.0
108
58.3
148
17.53K
-11
2523
29
543.7
69
157.6
109
56.8
149
Table 3 - Thermistor Resistance Versus Temperature
55.6
150

12
APPENDIX C. SAMPLE CALIBRATION REPORT
Figure 6 - Sample Model 6165 Calibration Report

13
APPENDIX D. PROGRAMMING THE MEMS TILT BEAM WITH CRBASIC
D.1 Description
CRBASIC is the programming Language used with Campbell Scientific CRBASIC Dataloggers.
Campbell’s Loggernet Software is typically used when programming in CRBASIC. The MEMS
sensor should be read with the VoltDiff instruction and the output averaged 100x. No Thermistor
in this example.
D.2 Sample Program
'Declare Public Variables for Reading MEMS Sensor
Public MEMS_1
Public MEMS_2
Public MEMS_3
Public MEMS_Output 'Output of the MEMS Sensor
'Store MEMS Output every 2 minutes
DataTable (MEMS_EXAMPLE,1,-1)
Sample (1,MEMS_Output,IEEE4)
EndTable
BeginProg
'2 min scan interval
Scan (2,min,0,0)
'Read MEMS Sensor on Differential Channel 1 and average 100x Readings
Delay(0,100,mSec)
MEMS_3 = 0
For MEMS_1 = 1 To 100
VoltDiff (MEMS_2,1,mV5000,1,False,0,250,0.001,0)
MEMS_3 = MEMS_3 + MEMS_2
Next
MEMS_Output = MEMS_3 / 100
CallTable MEMS_EXAMPLE