Geosense VW PIEZOMETERS Bedienungsanleitung
Version 1.4 May 09
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VW PIEZOMETERS
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Version 1.4 May 09
CONTENTS
1.0 INTRODUCTION Page 3
1.1 Applications
1.2 Theory of operation
2.0 CONFORMITY Page 6
3.0 MARKINGS Page 7
4.0DELIVERY Page8
4.1 Packaging
4.2 Handling
4.3 Inspection
4.4 Storage
5.0 INSTALLATION Page 10
5.1 Zero Pressure or Base Readings
5.2 Preparation for installation
5.3 Installation Procedures - Boreholes
5.4 Installation Procedures - Trenches & Pockets
5.5 Installation Procedures - Observation Wells or
as Water Level Sensor
5.6 Grouting
6.0 DATA HANDLING Page 33
6.1 Taking readings
6.2 Data reduction
7.0 MAINTENANCE Page39
8.0 TROUBLESHOOTING Page 39
9.0 SPECIFICATION Page 41
10.0 SPARE PARTS Page 42
11.0 RETURN OF GOODS Page 43
12.0 LIMITED WARRANTY Page44
13.0 APPENDIX Page45
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It is VITAL that personnel responsible for the
installation and use of the piezometers READ and
UNDERSTAND the manual, prior to working with the
equipment.
1.1 General Description
The Vibrating Wire Piezometer is an environmentally sealed sensor that is used to
register changes in fluid pressure, generally in, but not limited to, under ground
locations.
A Vibrating Wire Piezometer can be installed or included in many types of monitoring
regime and can be linked to various types of readout equipment.
The primary uses for piezometers are :-
Soil and rock pore pressure measurement.
Water level monitoring ( groundwater or open chambers )
With applications such as, but not limited to, the following :-
Embankment stability and safety monitoring
Measuring loads behind retaining walls
Assessing soil consolidation
Measurement of uplift pressures acting on structural foundations
Verification of seepage patterns and models
Slope stability monitoring
Water level monitoring for Environmental control
Tidal influence assessment
Pump Testing
Particular features of the MGS-Geosense piezometer are:-
Reliable long term performance.
Rugged; suitable for demanding environments.
High accuracy.
Insensitive to long cable lengths.
The Piezometer is based upon ‘industry standard’ Vibrating Wire technology. When
electronically excited, the sensor produces an output signal in the form of an
alternating current. The frequency of the alternating current can then be readily
converted to a fluid pressure by applying individual calibration factors.
(Continued on page 4)
1.0 INTRODUCTION
This manual is intended for all users of Vibrating Wire Piezometers manufactured by
MGS Geosense and provides information on their installation, operation and
maintenance.
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Frequency signals are particularly suitable for the demanding environment of civil
engineering applications, since the signals are capable of long transmission distances
without degradation. They are also somewhat tolerant of damp wiring conditions and
resistant to interference from external electrical noise.
The MGS-Geosense range of VW piezometers is supplied in various configurations to
suit varying installation environments and techniques. Each VW piezometer is fitted
with a length of connecting cable, an internal temperature sensor and a surge
arrestor. Each VW piezometer option is detailed in this manual, with its own specific
installation instructions.
(Continued from page 3)
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1.2 Theory of Operation
The Vibrating Wire Piezometer consists of a tensioned steel wire, anchored at one
end to a flexible diaphragm ( the sensing element ) and at the other end to the
Nimonic inner body, all sealed into a stainless steel body. The internal parts of all
MGS Geosense piezometers are identical, only the thickness of the diaphragm and
the geometry of the body changes.
Two opposing coils are located within the inner Nimonic body close to the axis of the
wire. When a brief voltage excitation, or swept frequency excitation is applied to the
coils, a magnetic field is induced causing the wire to oscillate at its’ resonant
frequency. The wire continues to oscillate for a short period through the ‘field’ of the
permanent magnet, thus generating an alternating current (sinusoidal) output. The
frequency of this current output is detected and processed by a vibrating wire readout
unit, or by a data logger equipped with a vibrating wire interface, where it can be
converted into ‘Engineering’ units of pressure.
As fluid pressure is applied to the exposed side of the flexible diaphragm, the
diaphragm deflects, causing a change in the tension of the wire behind it. The change
in tension of the wire results in a change in resonant frequency of oscillation of the
wire, with the square of frequency of oscillation being directly proportional to the
applied pressure.
For further information see Section 6 - Data Handling.
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2.0 CONFORMITY
Marton Geotechnical Services Ltd
Geotechnical Centre
Rougham Industrial Estate
Rougham, Bury St Edmunds
Declaration of Conformity
Declaration of Conformity
Document Number QF037 (Iss 2)
We Marton Geotechnical Services Ltd at above address declare under our sole responsibility that the
Geosense products detailed below to which this declaration relates complies with protection requirements
of the following harmonized EU Directives,
Low Voltage Directive 73/23/EEC (as amended by 93/68/EEC)
The Electromagnetic Compatibility Directive 2004/108/EC
The Construction Products Directive 89/106/EEC
Equipment description Vibrating Wire Piezometers
Make/Brand Geosense
Model Numbers VWP-3000, VWP-3001, VWP-3101, VWP-3200
VWP3201, VWP-3300, VWP-3400
This equipment has been designed and manufactured with reference to the following standards:
All mechanical drawings used in the production of this equipment are based upon BS 8888
Electrical/electronic drawings are based upon BS 3939.
A technical file for this equipment is retained at the above address
This Declaration of Conformity was prepared according to EN ISO/IEC 17050-1:2004.
Martin Clegg
Director
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3.0 MARKINGS
Geosense piezometers are labelled with the following information:-
Manufacturers name & address
Product type
Model
Serial number
CE mark
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4.3 Inspection
It is important to check all the equipment in the
shipment as soon as possible after taking delivery
and well before installation is to be carried out.
Check that all the components detailed on the
documents are included in the shipment. Check
that the equipment has not been physically
damaged.
ALL Geosense VW piezometers carry a unique
identification serial number which is located on the
cable close to the piezometer body and at the free
end of the cable ( see right ). All VW piezometers
are supplied with individual calibration sheets that
include their serial numbers and these will shipped
with the piezometers.
Calibration Sheets contain VITAL information about the
piezometer. They MUST be stored in a safe place. Only
(Continued on page 9)
4.0 DELIVERY
This section should be read by all users of Vibrating Wire
Piezometers manufactured by MGS Geosense.
4.2 Handling
Whilst they are a robust devices, VW piezometers are precision measuring
instruments. They and their associated equipment should always be handled with
care during transportation, storage and installation.
Once the shipment has been inspected ( see below ), it is recommended that
piezometers remain in their original packaging for storage or transportation.
Cable should also be handled with care. Do not allow it to be damaged by sharp
edges, rocks for example, and do not exert force on the cable as this my damage the
internal conductors and could render the installation useless.
4.1 Packaging
VW Piezometers are packed for transportation to site. Packaging is suitably robust to
allow normal handling by transportation companies. Inappropriate handling
techniques may cause damage to the packaging and the enclosed equipment. The
packaging should be carefully inspected upon delivery and any damage MUST be
reported to both the transportation company and MGS Geosense.
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4.4 Storage
All equipment should be stored in an environment that is protected from direct
sunlight. It is recommended that cables be stored in a dry environment to prevent
moisture migrating along inside them in the event of prolonged submersion of
exposed conductors.
During operational checks and establishing zero values, it will be necessary to
submerge the VW piezometers. Subsequent exposure to sub-zero temperatures
(Continued on page 10)
copies should be taken to site.
CHECK the piezometer ‘Zero Readings’
against the factory ‘Zero Readings’ on
arrival to ensure they have not changed
due to damage during transportation. To
do this, connect a Vibrating Wire readout to
the bare cable ends (Black and Red
conductors). – See readout manual for
connection guidance.
*NB If the readout display is in
‘Period’ units ( eg 0.03612 ) a
calculation must be performed to
convert to Hz2/1000 ( Linear Digits )
units, since the calibration sheet is
presented in Hz2/1000 units. The
Geosense Readout model VW200
displays the readings in ‘Period’. The
RST readout / logger unit Model
Number VW2106 displays the readings
in Linear digits. See Section 6 of this
manual for more information on units
and conversion routines.
Prior to carrying out a ‘Zero Reading’
CHECK, ensure that the piezometers have
been stored in a reasonably stable
temperature for at least 30– 60 minutes.
Record the values displayed on the readout ( and units ) against the piezometer
serial numbers. If these ‘out of the box’ CHECK readings show significant differences
( +/- 40 digits ) to the zero pressure values on the calibration sheets, contact MGS
Geosense for assistance. ( It should be noted that the ‘CHECK Readings WILL be
affected by the atmospheric pressure & altitude ).
If components are missing or damaged, contact the delivery company, the supplier
and / or MGS Geosense.
(Continued from page 8)
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may cause damage to the diaphragms if the water they contain is allowed to freeze.
Storage areas should be free from rodents as they have been known to damage
connecting cables.
No other special requirements are needed for medium or long-term storage although
temperature limits should be considered when storing or transporting associated
components, such as readout equipment.
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