ROCTEST FOD Manuale utente
INSTRUCTION MANUAL
SENSOPTIC FIBER-OPTIC DISPLACEMENT TRANSDUCER
Model FOD
Roctest Limited, 2000. All rights reserved.
This equipment should be installed and operated only by qualified personnel. Its misuse is potentially dangerous. The Company makes no warranty as to the information
furnished in this manual and assumes no liability for damages resulting from the use thereof. The information herein is subject to change without notification.
Tel.: 1.450.465.1113 • 1.877.ROCTEST (Canada, USA) • 33.1.64.06.40.80 (France) • 41.91.610.1800 (Switzerland)
www.roctest.com
E10169-001109
TABLE OF CONTENTS
1PRODUCT...............................................................................................................1
1.1 GENERAL............................................................................................................1
1.2 DESCRIPTION.....................................................................................................1
1.3 CALIBRATION......................................................................................................2
1.4 SPECIFICATIONS................................................................................................2
2READING PROCEDURE.........................................................................................3
2.1 INITIAL READINGS..............................................................................................3
2.2 DISPLACEMENT EQUATION..............................................................................3
2.3 INTERPRETATION ..............................................................................................3
3INSTALLATION.......................................................................................................4
4CABLE ....................................................................................................................4
E10169-001109 FOD
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1 PRODUCT
1.1 GENERAL
The fiber-optic displacement transducer is used to measure movements such as:
The opening or closing of construction joints in buildings, bridges and pipelines
The amount of opening or contraction of joints in concrete structures
Joint and crack openings within rock and concrete masses or at rock-concrete
interfaces.
The FOD is supplied with either an embedment type or surface-mounted installation
fixture.
All Roctest fiber optic readout equipments can read the FOD. Data acquisition systems
are also available. Contact manufacturer for more details.
The FOD is delivered with a calibration data sheet providing calibration factors to be used
in the displacement equation. The displacement equation converts readings units into
engineering units. The calibration factors are determined by factory calibration.
1.2 DESCRIPTION
Our unique design is based on a Thin Film Fizeau Interferometer device (TFFI) mounted
on a movable shaft. The TFFI can be seen as a spatially distributed Fabry-Perot cavity
where the cavity length varies along the lateral position. The optical fiber is mounted in a
manner that the tip is facing the surface of the TFFI, which is moved relative to the
optical fiber extremity. By connecting this device to one of Roctest’s white-light fiber-
optic readout unit, it becomes an absolute position and displacement transducer.
The FOD is totally immune to electromagnetic and radiofrequency (EMI/RFI)
interferences and carries no risk of current leakage or ignition. The FOD can be packed
in a very compact form and can be located far away (up to 2 km) from the readout unit.
These characteristics make the FOD well suited for difficult-to-reach locations and
hazardous environments such as those containing explosive materials.
The surface-mounted FOD is available in two models: FOD-F and FOD-J. The FOD-F is
mounted on an anchor block. Its loaded-spring spindle remains continuously in contact
with an anchored reference surface.
Model FOD-F
E10169-001109 FOD
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With the FOD-J confiuration, both extremities are fixed to ball joint linkages that mate
with the anchors. This model is fited with a telescopic plunger free to move in or out of
the housing as the distance between the measurement points varies. The FOD-J allows
for small latteral displacements.
Model FOD-J
Both configurations are available with groutable or expansion anchors.
1.3 CALIBRATION
All displacement transducers are individually calibrated before shipment.
A calibration sheet, supplied with each gage, included the following informations:
The serial number
The temperature during the calibration
The calibration factors: A, B, C, D, E
The conversion equation
The fiber optic cable type and its length
1.4 SPECIFICATIONS
Linear Stroke: 20 mm
Accuracy: ±0.1% of F.S.
Resolution: 0.002 mm
EMI/RMI susceptibility: Intrinsic immunity
Cable length: 1.5 meter length. Custom length up to 2 km and high
temperature cable available
Cable material: 4.0 mm O.D. polyurethane jacket (other material available)
Housing material: Aluminum or stainless steel
Connector: ST
Dimensions: 144 mm length x 19 mm O.D. (other size optionally available)
E10169-001109 FOD
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2 READING PROCEDURE
2.1 INITIAL READINGS
Gage readings should be taken as soon as the gages are received to ensure that they
have not been damaged during shipment. Please review the readout unit instruction
manual before proceeding with the reading.
Before a transducer can be used with the fiber-optic readout unit from Roctest, its gage
factor (0001000) must be first selected. The gage factor, already recorded in the memory
of the readout unit, is registered on a label installed on the cable close to the fiber-optic
connector and on the calibration sheet of the gage.
After that, readings displayed be the readout can be read and used it in the equation
supplied on the calibration data sheet to obtain the displacement in engineering units.
Steps before taking a reading
1. Select gage factor (0001000) in the readout memory
2. Associate gages to appropriate channel number and gage factor
3. Be sure that you have the displacement equation and the calibration factors
appropriate to each gage.
2.2 DISPLACEMENT EQUATION
The reading value on the readout unit must be converted in engineering unit such as
millimeter (mm) or inch (in) by the displacement equation supplied on the calibration
data sheet. The equation is:
Di = A L4+ B L3+ C L2+ D L + E (1)
where: Di = Displacement
A,B,C,D,E = Calibration factors given on the calibration data sheet
L = Current reading in unit
2.3 INTERPRETATION
The reading seen on the readout unit is the distance between the actual point and the
reference point (located at mid-range) established during factory calibration.
Therefore, it is necessary to fix your own reference point by taking an initial reading after
installation is completed. The initial displacement (D0), calculated with equation 1, gives
your reference displacement. Then you can compare the following reading (D1) to the
reference and compute the real displacement (Dreal).
E10169-001109 FOD
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The following equation indicates how to calculat real displacement.
Dreal= D1–D0 (2)
Note:
A positive value of Dreal indicates an increasing displacement (extension of shaft) and a
negative value indicates a decreasing displacement or contraction.
3 INSTALLATION
Prior installation of the fiber optic displacement transducer, a starting point must be
determined. This position must be:
Mid-range : to measure extension or contraction
End of range (shaft in complete extension): to measure mostly contraction
Beginning of range: to measure mostly extension
4 CABLE
The gage factor and the serial number corresponding to each FOD are stamped on a tag
fastened to the readout end of the cable. In option, the serial number is stamped along the
entire length of the cable. Should the cable be cut, we recommend the use of our cable
splice kits. Call the manufacturer for details.
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