Delta-T Devices PR2 Manuel utilisateur
User Manual for the
Profile Probe
type PR2
PR2-UM-3.0
Delta
-
T Devices Ltd
Notices
Copyright
All rights reserved. Under the copyright laws, this manual may
not be copied, in whole or in part, without the written consent of
Delta-T Devices Ltd. Under the law, copying includes translation
into another language.
Copyright © 2004, Delta-T Devices Ltd.
Patent pending
The Profile Probe has been developed by Delta-T Devices and
uses novel measurement techniques, patent pending.
CE conformity
The Profile Probe type PR2 conforms to EC regulations
regarding electromagnetic emissions and susceptibility when
used according to the instructions contained within this user
manual, and is CE marked by Delta-T Devices Ltd.
Design changes
Delta-T Devices Ltd reserves the right to change the designs
and specifications of its products at any time without prior notice.
User Manual Version: PR2-UM-3.0 Jan 2008
Delta-T Devices Ltd. Tel: +44 1638 742922
130, Low Road Fax: +44 1638 743155
CAMBRIDGE CB25 0EJ Web: www.delta-t.co.uk
UK
Contents
Introduction 4
Description 4
Parts list 6
Care and safety instructions 7
Routine maintenance 7
PR2 Cleaning and Chemical Avoidance
Instructions 8
How the Profile Probe works 9
Operation 10
Preparation for reading 10
Insert the Profile Probe 11
Portable monitoring 12
Record readings with a data logger 13
Calibration 17
Conversion to soil moisture 19
Reading accuracy 22
Troubleshooting 24
Problems 24
Technical reference 26
Specifications 26
Performance 27
Definitions 29
References 31
Technical Support 32
Soil-specific calibration 34
Laboratory calibration non-clay soils 35
Laboratory calibration for clay soils 37
Field calibration 40
Index 43
Introduction
Description
The Profile Probe measures soil moisture content at different
depths within the soil profile. It consists of a sealed
polycarbonate rod, ~25mm diameter, with electronic sensors
(seen as pairs of stainless steel rings) arranged at fixed intervals
along its length.
When taking a reading, the probe is inserted into an access
tube. The access tubes are specially constructed thin-wall
tubes, which maximise the penetration of the electromagnetic
field into the surrounding soil.
The output from each sensor is a simple analogue dc voltage.
These outputs are easily converted into soil moisture using the
supplied general soil calibrations or the probe can be calibrated
for specific soils.
Advantages
The Profile Probe is dual-purpose
each probe can be used both for portable readings from
many access tubes and for installation within one access
tube for long-term monitoring.
Fully sealed and robust.
High accuracy: ±4%.
Easy installation with minimal soil disturbance.
Large sampling volume ~ 1.0 litres at each profile depth.
olts
Works reliably even in saline soils.
Simple analogue output, 0 to ~1.0 V
4zIntroduction Profile Probe User Manual 3.0a
PR2/6 and
PR2
/
4 in
so
i
l
Electromagnetic
fields extend into
the soil and detect
soil moisture
Sensor 1
Pair of
sensor rin
g
s
1 metre
Profile Probe User Manual 3.0a Introduction z5
Parts list
Your consignment may have the following parts:
Part Sales Code Description
PR2/4 with 4 sensors (as
shown) or PR2/6 with 6
sensors. Both supplied in
protective tube, with spare o-
rings and centring springs
Profile Probe PR2/4
or
PR2/6
Access tube spacer Corrects PR2 depths when
access tubes are mounted
flush with soil surface
SPA1
Spares kit
PR2-SP
Cleaning kit Cleans access tubes
AT-CR1-
Bag Carrying bag for PR2
PR-CB2
Access tubes Short or long fibreglass tubes
suitable for PR2/4 or PR2/6,
including cap, bung and
collar.
ATS1
or
ATL1
Augering equipment - See Augering Manual
Insertion equipment - See Augering Manual
Extraction equipment - See Augering Manual
Meter Moisture meter plus
accessories
HH2
Data logger 6-channel data logger
optimised for PR2,
DL6
or or
DL2e General purpose multi-
channel logger adaptable for
many logging needs.
Cables 1.5m to HH2
PRC/d-HH2
5m to DL6
PRC/M12-05
5m to DL2e or other loggers
PRC/w-05
5m, 10m and 25m extension
cables (PRC/M12-05 and
EXT/M12-10 are identical)
EXT/M12-05
EXT/M12-10
EXT/M12-25
6zIntroduction Profile Probe User Manual 3.0a
Care and safety instructions
Keep your PR2 in its protection tube and fit the
connector cap when the probe is not in use. The Profile
Probe should be stored in a dry environment (definitely
non-condensing), and protected from sharp blows
Earth yourself on the metal connector before touching
the detector rings to avoid any possibility of damage by
electrostatic discharge.
Don’t lay the PR2 in a puddle because water may creep
under the rings – if you suspect this has happened warm
gently (< 50°C) for 24 hours.
minimise any electrical interference with other equipment.
Lay as much of the cable as possible along the
surface of the soil when taking a reading in order to
Routine maintenance
.
into an
e
ould be returned for routine re-calibration every 5
years.
Periodically examine the o-rings and centring springs
They should be kept clean, and if they show any signs of
damage, replace them. Pay attention particularly to the
lowest centring spring when inserting the PR2
access tube – a gentle twisting action helps.
The Profile Probe should be periodically recalibrated.
You should run a simple annual check on the calibration
(see the Troubleshooting section) and contact your local
Delta-T representative if there is a problem. Otherwise th
PR2 sh
Profile Probe User Manual 3.0a Introduction z7
PR2 Cleaning and Chemical Avoidance
Instructions
The PR2 shaft is made of polycarbonate plastic which is an
exceptionally strong material, and it can withstand bending
forces far in excess of anything likely to be encountered in
practice. However, polycarbonate can develop stress cracking
when exposed to certain chemicals. Such stress cracking greatly
weakens the polycarbonate and may lead to brittle fracture of the
shaft, even at very low stresses.
It is important to follow these guidelines. Failure to observe these
precautions can damage the probe and may invalidate the
warranty.
Clean the probe in use if necessary by wiping with damp
plain paper towels.
Use only clean water to damp the paper. Do not use
chemicals or cleaning agents of any sort in the water.
Never use any chemical solvents or cleaners on the probe,
or near to it. Avoid strong chemical vapours, especially
during probe storage.
, allow
is thoroughly dry before storing it in
the protection tube.
Do not immerse the probe in water. If this happens
the probe to dry in warm air for at least 24 hours.
Make sure the probe
8zIntroduction Profile Probe User Manual 3.0a
How the Profile Probe works
Before you rush out and hammer your access tubes into the soil,
it will help to understand a little about how the Profile Probe
works:
When power is applied to the Profile Probe...
...it creates a 100MHz signal (similar to FM
radio).
The signal is applied to pairs of stainless steel
rings....
... which transmit an electromagnetic field
extending about 100mm into the soil.
The field passes easily through the access tube
walls, but less easily through any air gaps.
The water content of the soil surrounding the
rings...
...dominates its permittivity.
ε(A measure of a material’s response to
polarisation in an electromagnetic field. Water
has a permittivity ≈81, compared to soil ≈4 and
air ≈1)
The permittivity of the soil has a strong
influence on the applied field…
Vout …resulting in a stable voltage output that…
...acts as a simple, sensitive measure of soilSoil Moisture
moisture content.
22 %
Profile Probe User Manual 3.0a Introduction z9
Operation
Preparation for reading
Install access tubes
The Profile Probe must be used within an access tube. The
process of augering holes and installing access tubes is
described in the Augering Manual.
Equipment
You may require the following equipment for a site visit:
PR2 in
p
rotective tube
Access tube spacer
Spare
collars
caps
centring
springs
If setting up
logging:
Data logger (DL6 or
DL2e) and cable
For portable
reading: HH2
meter and
cable
Roll of paper
towels
Cleaning rod
10 zOperation Profile Probe User Manual 3.0a
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