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Clinometers for
Structural Engineering
CEE 398
Ping Gu
University of Illinois
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Outline:
Application and Classification
Optical Inclinometer
Mechanical Inclinometer
Electrical Inclinometer Capacitive Accustar
Inductive RVDT
Resistive RPS and Applied Mechanicss tiltmeter
Special Issue: Clinometers for dynamic testing RVDT
Clino2000
Force Balance Inclinometers
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Application: Clinometers are also called inclinometers, tiltmeters. the performance of structures under loads, such as curvature of beams and plates
the effects of excavation and tunneling on existing structures
the rotation of dams, piles, retaining walls, struts, anchors,pipelines
road grading and paving
pipeline leveling
crane overturning-moment alarms
Classification according to reference-system:
gravity referenced: angle w.r.t. vertical gravity vector locally referenced: angle w.r.t its housing
according to principle:
Optical
Mechanical
Electrical
Applicationand Classification
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360 degree range
1 sec reading,
estimations to 0.2 use bubble
Static only
single reading
Optical Inclinometer
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Coincidence Lever
bubble
screw
accuracy: 0.25 sec
sigle reading by eye, static only
Pendulum Clinometer
pendulum
gravity referenced accuracy: 1min 30 sec
single reading by eye, static only
Mechanical Inclinometer
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Capacitive:
AccuStar
Clino2000
Inductive: RVDT
Resistive:
RPS Applied Mechanicss tiltmeter
Other types, such as strain-gage transducers, force
balance inclinometers
Electrical Inclinometer
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AccuStar
Size: 2.6 in diameter 1.2 in height
Weight: 20 oz
Total range: +/- 60 degree
Linear range: +/- 45 degree Resolution: 0.001 degree
Linearity: +/- 0.1 degree in 10
Temperature range: -30~65C Output: digital pulse width; serial
data; ratiometric; analog
Price: $139
Capacitorplate
intwo halves
etchedtoformtwovariablecapacitors
dielectricliquidandinert
gas
half-filled
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RVDT Principal: similar to LVDT
two primary coils and two secondary coils wound symmetrically on a large-diameter insulated robbin
magnetic cardioid-shaped rotor
mutual inductance varies and produces an output
Range: 20 degree Linearity: 0.5% ~ 1.0% fsd
Size: 38.1mm in diameter, 40mm in height
Weight: 250g
Supply voltage: 3V ac to 30V ac Can be used for dynamic testing
Advantages and disadvantages: similar to LVDT (see my filePotentiometers)
Locally referenced
Usin}
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RPS (Rotary Position Sensors) Principal: similar to POT, except that the wires are wound on a cylindrically shaped
core.
IT9101: magnetically-damped pendulum; conductive plastic film
Range: 0-45 degree
Resolution: essentially infinite
Accuracy: 2.0% full stroke
Size: 5 inches in diameter, 3.73 inches in thickness Weight: 11 lb
Supply voltage: 30V AC or DC
Can not be used for dynamic testing, but can withstand up to 10g to 2000Hzenvironmental shock with its added damping
Advantages and disadvantages: similar to POT (see my file Potentiometers)
Locally referenced
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Applied Mechanicss tiltmeter Resistive, gravity referenced
Principle: Size: 2x2x0.64 inch Weight: 15 g
Range: 25
Resolution: 0.01 microradians ($0.0006) Linearity: 1% over half span, 2.5% over full span
Supply voltage: +8 to +24 VDC @7mA
Analogue or digital outputs
Measure rotation in two orthogonal verticalplanes
High damping of vibration, being used for dam
and earthquake monitoring
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Special Issue: Clinometers for Dynamic Testing RVDT
Clino 2000 Priciple:
pendulum suspended by the Archimedes helical spring, between two electrodes
pendulum swing, changing the capacity between the pendulum and the twoelectrodes
RC-oscillator transforms capacities into different frequencies
the ratio of the two frequencies available is used as the primary signal
patent protected in most countries
Price: $2760
Range: 45 temperature compensation
Highest possible precision
resolution depends on sampling time
Max error in 24hr for 10 range: 0.055%FS+0.15% RO
integrated DYNAM calculating and displaying static and dynamic inclinations
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Special Issue: Clinometers for Dynamic Testing(continued)
Force Balance Inclinometers Principle: closed-loop torque or force balance servo system
torsional flexure-supported moving mass
servo system electronics
torque motor feedback sensor
gravity-referenced
Lucas Control Systems
Ranges available: 1 to 90
Shock survival: 1500g Vibration endurance-sinusoidal: 50g
Vibration endurance-random: 35g rms, 20 Hz to 2000 Hz
Respond to changes in angle 0.1 sec or slope 0.000006 inch/foot
Hysteresis less than 0.0005% of full range
Many angular accelerometers are based on the same priciple.
PositionsensorMass
Torquemotor
Electronics
Damping
ServoAmp
DC output
DC input
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Conclusion:
Optical Inclinometer
Mechanical Inclinometer
Electrical Inclinometer
Capacitive Accustar Clino2000
Inductive RVDT
Resistive RPSand Applied Mechanicss tiltmeter
Other types: Force Balance Inclinometers
Those underlined are suitable for dynamic testing
Those bold-faced are locally referenced, others are gravityreferenced.