Inclinometer Probe Manual
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . 1
The Inclinometer Probe . . . . . . . . . . . . . 2
Control Cable . . . . . . . . . . . . . . . . . . . . . . 4
Taking Readings . . . . . . . . . . . . . . . . . . . . 6
Data Reduction. . . . . . . . . . . . . . . . . . . . . 8
Inspection and Maintenance. . . . . . .12
Digitilt Inclinometer Probe Manual, 11/2011
Introduction
Inclinometer
System
An inclinometer system includes inclinometer casing, an inclinometer probe and
control cable, and an inclinometer readout unit.
Inclinometer casing is typically installed in a near-vertical borehole that passes
through a zone of suspected movement. The bottom of the casing is anchored in
stable ground.
The inclinometer probe is used to survey the casing and establish its initial position. Ground movement causes the casing to move away from its initial position.
The rate, depth, and magnitude of this movement is calculated by comparing data
from the initial survey to data from subsequent surveys.
This Manual
This manual addresses the use and maintenance of the inclinometer probe and
control cable. It also provides an overview of taking readings and reducing data.
Other manuals cover casing installation, inclinometer readouts, and software for
reducing data.
Digitilt Inclinometer Probe Manual, 11/2011
1
The Inclinometer Probe
The inclinometer probe consists of a stainless steel
body, a connector for control cable, and two pivoting wheel assemblies.
Control cable
Connector for
control cable
When properly connected to the control cable, the
probe is waterproof and has been used deeper than
1000 feet.
Upper wheel of
upper wheel
assembly
The wheel assemblies consists of a yoke and two
wheels. One of the wheels in each assembly is
higher than the other. This wheel is called the
“upper wheel” and has special significance, as
explained below.
Measurement
Planes
Upper wheel of
lower wheel
assembly
The inclinometer probe employs two forcebalanced servo-accelerometers to measure tilt.
One accelerometer measures tilt in the plane of the
inclinometer wheels. This is the “A”axis. The other
accelerometer measures tilt in the plane that is
perpendicular to the wheels. This is the “B” axis.
Positive tilt
readings
Top
The drawing at right shows the probe from the
top. When the probe is tilted toward the A0 or B0
direction, readings are positive. When the probe is
tilted in the A180 or B180 directions, readings are negative.
Orientation
of the Probe
Inclinometer casing is installed so that one set of
grooves is aligned with the expected direction of
movement. One groove, typically the “downhill”
groove should be marked A0.
In a standard inclinometer survey, the probe is
drawn from the bottom to the top of the casing
two times. In the first pass, the upper wheels of
the probe should be inserted into the A0 groove.
This ensures that movements are positive
values.
Digitilt Inclinometer Probe Manual, 11/2011
Negative tilt
readings
SE SOR2c c
A0 “downhill” groove
Upper
Wheel
Probe
Expected Direction of Movement
Parts of the Probe
Always start surveys with
upper wheel in A0 groove.
2
Handling
the Probe
The inclinometer probe is a sensitive measuring instrument. Handle it with care.
• Transport the probe in its carrying case. If you drive to the site, carry the casing
in the passenger compartment, preferrably on a passenger seat.
•
When you connect control cable to the probe, avoid overtightening the nut, since
this will flatten the O-ring and reduce its effectiveness.
• Before you lower the probe into the casing, turn the power on.
• When you insert the probe into the casing, cup the wheels with your hands to
compress the springs and allow smooth insertion.
•
When you lower the probe into the borehole, do not allow it to strike the bottom.
• When you withdraw the probe from the casing, again cup the wheels with your
hands to prevent them from snapping out.
•
When you rotate the probe, keep it upright and perform the rotation smoothly.
• The probe is rated for temperatures from -20 to 50 °C (-4 to 122 °F). Avoid using
the probe in temperatures outside this range.
Caring for the
Probe
This is an overview. See the last chapter, Inspection and Maintenance, for additional information.
Cleaning the Probe: When you finish a survey, wipe moisture off the probe and
replace the protective cap. If necessary, rinse the probe in clean water or wash it
with a laboratory grade detergent when you return to the office.
Cleaning the Connectors: Do not clean connectors with spray lubricants or electri-
cal contact cleaners. Solvents in these products will attack the neoprene inside the
connector. When it is necessary to clean the connectors, use a cotton swab slightly
moistened with alcohol. Be careful to use only a small amount of alcohol.
Drying the Probe: When you return to the office, remove protective caps from the
control cable, probe, and readout unit. Allow connectors to air-dry thoroughly for a
number of hours. Afterwards, replace the caps.
Storing the Probe: The probe, control cable, and readout unit should be stored in a
dry place. For extended storage, keep the probe in a vertical position.
Lubricating the Wheels: Lubricate the wheels regularly. Spray a small amount of
lubricant or place a drop of oil on both sides of the wheel bearings. Check that the
wheels turn smoothly.
O-Ring Care: Periodically clean and lubricate the O-ring on the connector end of
the inclinometer probe. Use O-ring lubricant.
Digitilt Inclinometer Probe Manual, 11/2011
3
Control Cable
Introduction
Control cable is used to control the depth of the inclinometer probe. It also conducts power to the probe and returns signals to the readout.
•
Metric control cables are graduated with yellow marks at 0.5 meter intervals and
red marks at 1-meter intervals. There are numeric marks at 5-meter intervals.
• English control cables are graduated with yellow markers at 2-foot
intervals and red markers at 10-foot intervals. There are numeric labels at every
red marker (ten-foot intervals).
Depth Control
Accurate inclinometer measurements depend on consistent
placement of the inclinometer probe. Always align the depth
marks on the control cable with the same reference. Aim for
placement repeatability of 6 mm (1/4 inch) or better.
We recommend using a pulley assembly to assist with depth
control. The jam cleat on the pulley assembly holds the cable
and the top edge of the chassis provides a convenient reference for cable depth marks.
The small pulley assembly is used with 48 mm and 70 mm
casing (1.9 and 2.75 inch). The large pulley assembly is used with 70 mm and 85
mm casing (2.75 and 3.34 inch).
Using the Pulley
Assembly
1.
Remove the pulley from the chassis.
2.
Clamp the chassis to the top of the casing.
3.
Insert the inclinometer probe and control cable.
4.
Replace the pulley.
Note: The distance between the top edge of the pulley chassis and the top of the
casing is one foot. Your data reduction software can automatically adjust for this, so
keep your survey procedure simple: use the marks on the cable and the top edge of
the pulley chassis for reference. Let the software do any extra work required.
Check that operators consistently use the pulley assembly. If the pulley is used for
one survey and not for the next, the resulting data sets will not be directly comparable. Sometimes a monument case or a protective pipe makes it impossible to attach
the pulley assembly to the casing. In this case, you can make a removable adapter
for the pulley assembly. If you use an adapter, be sure to use it consistently.
Digitilt Inclinometer Probe Manual, 11/ 2011
4
Cable Tips
Connecting Cable: When you connect control cable to the probe, avoid overtight-
ening the nut, since this will flatten the O-ring and reduce its effectiveness.
Calibrate your Cable: If you have time, “calibrate” your cable, recording the exact
position of cable marks. This can be important for long term monitoring projects.
Caring for Cable
Cleaning the cable: If necessary, rinse the cable in clean water or wash the cable in a
laboratory-grade detergent, such as Liquinox.® Do not use solvents to clean the
cable. Be sure the protective cap is in place before immersing the end of the cable in
water. Do not immerse the Lemo connector.
Cleaning Connectors: If it is necessary to clean the connector, use a cotton swab
moistened with a small amount of alcohol. Do not use spray lubricants or electric
contact cleaners. Solvents contained in such products will attack the neoprene
inserts in the connectors.
Drying Connectors: When you return to the office, remove protective caps from the
control cable, probe, and readout unit. Allow connectors to air-dry well for a number of hours.
Storage: Store cable on a cable reel when possible. The reel should have a mini-
mum hub diameter of 300 mm (12 inches). If a reel is not available, use the technique below to coil the cable.
Coiling Cable
1.
Loop cable forward as shown in
drawing.
2.
Twist cable backwards to make a
second loop as shown in drawing.
3.
Continue coiling cable, alternating
loops as in steps 1 and 2.
Digitilt Inclinometer Probe Manual, 11/201
5
Taking Readings
Good Practices
•
Use the same probe and control cable for each survey, if possible.
• Use a pulley assembly, if possible. It protects the control cable and provides a
good reference.
•
Use a consistent top reference. The goal is placement repeatability within 5 mm
or 1/4 inch. If one technician uses a pulley and another technician does not,
probe positioning will be inconsistent, and data will have to be manipulated
before it is useful.
• Always draw the probe upward to the reading depth. If you accidentally draw the
probe above the intended depth, lower the probe down to the previous depth,
then draw it back up to the intended depth. This technique ensures the probe will
be positioned consistently.
•
Wait 10 minutes for the probe to adjust to the temperature of the borehole.
• Wait for displayed readings to stabilize as much as possible. If the readings do not
stabilize, try to record an average reading.
Setting Up
Position the Probe
1.
When you arrive at the site, lay out a plastic sheet or tarp to set the equipment
on. You should have the inclinometer probe, the indicator, the control cable, and
the pulley assembly. Some people find it is useful to bring a basket or box to hold
the control cable and a rag to wipe off the probe and cable after readings have
been taken.
2.
Unlock and remove the protective cap from the casing. Attach the pulley
assembly.
3.
Remove protective caps from probe and control cable.
4.
Align the connector key with the keyway in the probe. Then insert the connector
and tighten the nut to secure the connection. Do not over-tighten the nut, since
this will flatten the O-ring and reduce its effectiveness.
1.
Turn on the indicator. This energizes the accelerometers, making them less susceptible to shock.
2.
Insert the probe into the casing with the upper wheels of both wheel assemblies
in the A0 groove. (Cup the wheels with your hands to compress the springs for a
smooth insertion). If you are using the pulley assembly, take out the pulley
wheel, insert the probe, and then replace the wheel.
3.
Lower the probe slowly to the bottom. Do not allow it to strike the bottom. Allow
the probe to adjust to the temperature inside the casing. Five or ten minutes is
usually sufficient.
Digitilt Inclinometer Probe Manual, 11/20
6
Record Data
Leaving the Site
At the Office
1.
Raise the probe to the starting depth. Wait for the numbers on the readout to stabilize. If you are using the DataMate, press the button to record both the A and B
axis readings. If you are using a manual indicator, write down the A-axis reading,
then switch to the B-axis and record that reading.
2.
Raise the probe to the next depth. Wait for a stable reading, and then record it.
Repeat this process until the probe is at the top of the casing.
3.
Remove the probe and rotate it 180 degrees, so that the lower wheels of both
wheel assemblies are inserted into the A0 groove. When you remove the probe,
cup the wheels with your hands to prevent them from snapping outwards. Also,
hold the probe upright when rotating it.
4.
Lower the probe to the bottom, raise it to the starting depth, and continue the
survey. Take readings at each depth until you have reached the top. Remove the
probe. At this point, you may want to validate the data set and make any corrections necessary.
Wipe off the probe and cable. Replace end-caps on cable and probe and return the
probe to its protective case. Replace the indicator’s protective plugs. Coil the cable.
Remove the pulley assembly and replace and lock the protective cap.
Wipe off the indicator and recharge its batteries. Transfer the data set to a PC. Oil
the probe wheels. If the storage place is dry, remove protective caps from probe,
indicator, and control cable to allow all connectors to dry.
Digitilt Inclinometer Probe Manual, 11/20
7
Data Reduction
The inclinometer probe measures tilt, rather than lateral movement.
How does tilt provide information about lateral movement? The
basic principle involves the sine function, an angle, and the hypotenuse of a right triangle. We are interested in the length of the side
opposite the angle θ.
enus
e
side opposite
hypo
t
Inclinometer
Measurements
side opposite
sin θ = --------------------------------hypotenuse
side opposite = hypotenuse × sin θ
Deviation
In the drawing at right, the hypotenuse of the right triangle
is the measurement interval. The measurement interval is
typically 0.5 m with metric-unit inclinometers or 2 feet
with English-unit inclinometers.
The side opposite the angle of tilt is deviation. It is calculated by multiplying the sine of the angle of tilt by the measurement interval. This calculation translates the angular
measurement into a lateral distance and is the first step to
calculating lateral movement.
Cumulative
Deviation
By summing and plotting the deviation values obtained at
each measurement interval, we can see the profile of the
casing.
Angle of Tilt
q
L
Measurement
Interval
Cumulative
Deviation
d1 + d2 + d3
The black squares at each measurement interval represent
cumulative deviation values that would be plotted to
show the profile of the casing.
θ3
d1 + d2
θ2
d1
θ1
d 1 = L x sinθ1
d 2 = L x sinθ2
d 3= L x sinθ3
d n = L x sinθn
Digitilt Inclinometer Probe Manual, 11/20
8
Displacements
Changes in deviation are called displacements, since the change indicates that the
casing has moved away from its original position. When displacements are
summed and plotted, the result is a high resolution representation of movement.
Incremental displacement plot
shows movement at each
measurement interval. The
growing “spike indicates a
shear movement.
Digitilt Inclinometer Probe Manual, 11/2011
Cumulative displacement plot
shows a displacement profile.
Displacements are summed from
bottom to top.
9
Reducing Data
Manually
Normally, computer software is used to reduce inclinometer data. Here, we show
only a simple overview.
Displayed Readings
Slope Indicator’s readouts display “reading units” rather than angles or deviation.
Reading units are defined below:
Displayed Reading = sin θ × Instrument Constant
Reading English = sin θ × 20,000
Reading Metric = sin θ × 25,000
Combining Readings
The standard two-pass survey provides two readings per axis for each interval. The
probe is oriented in the “0” direction for the first reading and in the “180” direction
for the second reading. During data reduction, we find the algebraic difference of
the two readings, and then we divide by 2, since there were two readings. Use of the
algebraic difference lets us preserve the direction of the tilt, as indicated with a positive or negative sign.
A0 Reading = 359
A180 Reading = – 339
Algebraic Difference 359 – ( – 339 )
---------------------------------- = ---------------------------------- = 349
2
2
Calculating
Deviation
To calculate lateral deviation, we find the algebraic difference of the two readings,
divide by 2, divide by the instrument constant, and multiply by the measurement
interval. In the example below, the English-unit measurement interval is 24 inches
and the English-unit instrument constant is 20,000.
Lateral Deviation = Measurement Interval x sin θ
359 – ( – 339 )
= 24 inches × ---------------------------------2 × 20, 000
= 0.4188 inches
Calculating
Displacement
Find the algebraic difference of the A0 & 180
readings and divide by 2.
Divide reading unit by instrument
constant to obtain sine of angle.
Displacement, the change in lateral deviation, indicates movement of the casing. To
calculate displacement, we need two surveys. We subtract the algebraic difference of
the initial reading from the algebraic difference of the current reading, divide by 2 x the
instrument constant, and multiply by the length of the measurement interval.
Algebraic Difference current = 700
Algebraic Difference initial = 698
Displacement = Measurement Interval × ∆ sin θ
700 – 698
= 24 inches × ---------------------------2 × 20, 000
= 0.0012 inches
Digitilt Inclinometer Probe Manual, 11/201
10
Calculating
Checksums
A checksum is the sum of a “0” reading and a “180” reading at the same depth.
A0 reading = 359
A180 reading = -339
Checksum = 359 + (-339)
= 20
Bias (zero offset)
If you hold your inclinometer probe absolutely vertical and check the reading, you
will typically see a non-zero value for each axis. The non-zero value is the result of a
slight bias in the output of the accelerometers. The bias (or zero offset) may be negative or positive and will change over the life of the probe. This is not normally a
matter for concern, because the zero offset is effectively eliminated by the standard
two-pass survey and the data reduction procedure.
Below, we show an readings that have a zero offset of 10. During the first pass the
probe measures a tilt of 1 degree. During the second pass the probe measures a tilt
of -1 degree, because it has been rotated 180 degrees. See how the offset increases
the positive reading and decreases the negative reading, even though the measured
angle has not changed. However, when the two readings are combined, as discussed
in “Combining Readings” above, the offset is eliminated and the correct value
emerges.
y (reading)
m (sensitivity)
b (zero offset)
x (degrees)
Tilt angle = 1 degree. Theoretical reading unit = 349
( 20,000 x sin (1) )
Offset = 10
Displayed A0 reading = 359
( 349 + 10 )
Displayed A180 reading = -339
( -349 + 10 )
Algebraic Difference = 698
( 359 - (-339) )
Algebraic Difference
---------------------------------- = 349
2
Digitilt Inclinometer Probe Manual, 11/2011
11
Inspection & Maintenance
Probe
Inspection
Probe
Maintenance
Part
What to check for
Remedy
Wheel yoke
Side to side movement
Check pivot pin, which looks like screw. If pivot pin has
been turned too far, it may spread the wheel yoke. Turn
the pivot pin counter-clockwise to see if movement disappears. If movement persists, replace the nylon spacers
or the entire wheel assembly. The wheel assembly can be
replaced by the user: kit number 50302555.
Wheel yoke
Yoke does not return to
fully extended position.
If yoke is dirty, clean it. If problem persists, spring may be
broken or weak. Replace spring and roll pins or replace
wheel assembly using kit 50302555.
Wheel
Side to side movement
Bad bearing. Replace wheel assembly.
Wheel
Does not turn freely
Lubricate. If movement is still bad, replace wheel assembly.
Body screws
Loose screws, wobble in
body, loose bumper
Tighten screws. (Do not tighten pivot pin).
Connector
keyways
Wear, corrosion
Worn keyway may degrade O-ring seal. Learn how to
connect cable without “hunting.” Remove corrosion and
change practice - allow connector to dry after use.
Connector
O-ring
Flattened, split
Replace if flattened or split.
Connector
pins
Bent pins
Bent pins are easily broken when straightened. Replacement of connector requires recuperation of probe
(expensive). Change connection practice - no hunting.
Moisture Management
Wipe off the control cable and probe when you finish the day’s final
survey, then wipe off the probe. Do not store wet cloth with the probe.
Allow the connector to dry thoroughly: remove connector cap and
allow connector to air-dry for a number of hours. Lubricate the
wheels. This helps displace moisture.
Wheels
Lubricate the wheels by spraying a small amount of lubricant or placing drops of oil on both sides of the wheel bearings.
O-Ring
Lubricate regularly with O-ring lube or silicone based grease. Do not
use WD-40 or any other lubricant spray that contains chlorinated solvents.
Connectors
Clean connectors as necessary. Use a slim cotton swab moistened
with alcohol. Be careful not to bend pins.
Do not use electrical contact cleaners, especially sprays. Solvents in
these products will attack the neoprene inside the connectors. When
attacked, the neoprene swells and reduces the effectiveness of the Oring seal.
Storage
Store probe in dry place. Be sure that the box is dry, the wheels are
oiled, the connector is dry.
If probe is to be stored for an extended period, stand it vertically.
Digitilt Inclinometer Probe Manual, 11/2011
12
Control Cable
Inspection
Control Cable
Maintenance
Part
What to check for
Remedy
Cable
Continuity
If you have intermittent failures, perform continuity tests.
If a wire fails continuity test, you can check the Lemo connector or return cable for servicing or replacement.
Cable
Twists, worn markings,
kinks, gouges
Twists indicate poor coiling technique. Change practice:
use cable reel, figure-8 coils, or over-under coils.
Worn markings: user is dragging cable over the edge of
the casing. Change practice - but must keep consistent
depths.
Kinks: if kinks do not straighten, there is probably internal
damage and likelihood of intermittent reading failures. If
any deep gouges, water can enter cable. In both cases,
bad section of cable must be removed, either by shortening the cable or replacing the cable.
Connector
key
Wear, corrosion
Change connection practice - no hunting. Remove corrosion and change practice - allow connector to dry after
use.
Connector
rubber insert
Swelling, poor seal
Rubber swells when attacked by WD-40 or contact cleaners. Swelling may prevent good seal and allow water to
enter connector.
Return for service if sealing is compromised.
Connector for
Indicator
(Lemo)
Corrosion, bad connection.
Perform continuity check first. Then check this connector
to eliminate as possible source of intermittent failures.
Unscrew bottom nut, being careful not to twist cable.
Slide shell off the end of the cable. Slide strain relief collet
out of the way and inspect connections. Twist and pull
wires gently. Good connections will not break. Repair as
necessary.
Connector for
Probe
Check O-ring
Do not disassemble this connector. Requires about two
hours and a pressure test to reassemble.
Moisture Management
Wipe off the control cable as you draw the probe up on the last run of the
day.
When you return to the office, remove connector caps and allow connectors
to air-dry for a number of hours.
Cable
When necessary, rinse cable (but not connectors) in clean water or wash the
cable in a laboratory-grade detergent, such as Liquinox.
Do not use solvents to clean the cable.
Connectors
If it is necessary to clean the connector, use a cotton swab moistened with
alcohol. Sockets can be cleaned with a brush.
Do not use spray lubricants or electric contact cleaners. Solvents contained
in such products will attack the neoprene inserts in the connectors.
Storing Control Cable
Improper coiling of any electrical cable twists conductors and can cause reliability problems. There are several ways to control twisting:
• Use cable reel with hub diameter of at least 200mm or 8”.
• Coil cable in a figure-8.
• Coil cable using over-under loops (2-foot diameter loops).
Digitilt Inclinometer Probe Manual, 11/2011
13
Control Cable
Connectors
Testing
Below is the wiring diagram for the connectors on the control cable.
Connectors are made to mate with each other but not with any other objects. Never
insert the probe of your multimeter into a socket. In making the measurements
below, simply touch the probe to the top of the socket.
Continuity Test: Pin 1 to Pin A, Pin 2 to Pin B, etc, should measure a little less than
1 ohm per 30 m (100 feet).
Isolation Test: Pin to pin should measure infinity. Also any pin to the body of the
connector should measure infinity.
Servicing
Use caution when attempting to service either connector.
The Lemo connector on the indicator end of the cable is easier to
service. When you disassemble the connector, be sure that you do not twist the
cables.
The heavy connector on the sensor (probe) end of the cable is more
difficult to service. We recommend that you send it to the factory unless you are
experienced and are willing to spend some time working with it.
Digitilt Inclinometer Probe Manual, 11/2011
14
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF

advertising