UMS T5 User manual

© UMS GmbH München
Art.Nr. T5
Version 12/2009
Author: tk, ge, ma
User Manual
Pressure Transducer Tensiometer
T
T5 5/ /T T5 5
x
x

Introduction
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Table of content
1Introduction 4
1.1 Safety instructions and warnings 4
1.2 Content of delivery 5
1.3 Foreword 6
1.4 Guarantee 6
1.5 Durability 6
1.6 Tensiometer T5 and T5x 7
1.6.1 Soils and soil water 7
1.6.2 Intended use 7
1.6.3 Typical applications 8
1.6.4 Extended measuring range of the T5x 8
1.6.5 Specific notes 9
1.7 Quick installation guide 10
2Sensor description 12
2.1 Design 12
2.1.1 Body and shaft 12
2.1.2 Pressure transducer 12
2.1.3 Reference air pressure 12
2.1.4 The ceramic tip 13
2.2 Analog output signals 13
3Installation 14
3.1 Scientific measure ideas 14
3.1.1 Selecting the measuring site 14
3.1.2 Number of Tensiometers per level 14
3.1.3 Extension of the site 14
3.1.4 Ideal conditions for installation 15
3.1.5 Documentation 15
3.1.6 Selecting the installation angle 15
3.2 Installation procedure 16
3.3 Offset correction for non horizontal installations 17
3.4 Connecting T5 and T5x 18
3.4.1 Spot readings with the INFIELD7 18
3.4.2 Cables 18
3.4.3 General requirements 18
3.4.4 TV-batt Tensiometer power supply 19
3.4.5 Connection to a data logger 19
3.4.6 Tensiometer loggers DL6-te or GP1-te 19
4Service and maintenance 20
4.1 Refilling 20
4.1.1 When do Tensiometers need to be refilled? 20
4.1.2 Refilling T5 in lab and field 20
4.2 Testing 32
4.2.1 Calibration 32
4.2.2 Check the Offset 32
4.3 Cleaning 33

Introduction
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4.4 Storage 33
5Protecting the measuring site 33
5.1 Theft and vandalism 33
5.2 Cable protection 33
5.3 Frost 33
6Useful notes 34
6.1 Extended measuring range 34
6.1.1 The bubble point of the porous cup 34
6.1.2 The vapour pressure of water 34
6.1.3 Boiling retardation: 35
6.2 Maximum measuring range and data interpretation 36
6.3 Temperature influences during measurements 38
6.4 Vapour pressure influence on pF/WC 38
6.5 Osmotic effect 39
7Troubleshooting 39
8Appendix 40
8.1 Technical specifications 40
8.2 Wiring configuration 41
8.3 Accessories 42
8.3.1 Connecting and extension cables 42
8.3.2 Handheld measuring device 43
8.3.3 Tensiometer loggers 43
8.3.4 TV-batt power supply 44
8.3.5 T5 auger kit 44
8.3.6 T5-case 44
8.4 Units for soil water and matrix potentials 45
8.5 Index 46
Your addressee at UMS 48

Introduction
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1 Introduction
1.1 Safety instructions and warnings
Electrical installations must comply with the safety and EMC
requirements of the country in which the system is to be used.
Please note that any damages caused by handling errors are out of
our control and therefore are not covered by guarantee.
Tensiometers are instruments for measuring the soil water tension,
soil water pressure and soil temperature and are designed for this
purpose only.
Please pay attention to the following possible causes of risk:
Lightning: Long cables act as antennas and might conduct surge
voltage in case of lightning stroke – this might damage sensors
and instruments.
Frost: Tensiometers are filled with water and therefore are
sensitive to frost! Protect Tensiometers from frost at any time.
Never leave Tensiometers over night inside a cabin or car when
freezing temperatures might occur!
Tensiometers normally are not damaged when the cup is
installed in a frost free soil horizon (in general below 20 cm).
Excess pressure: The maximum non destructive pressure is
300 kPa = 3 bar = 3000 hPa. Higher pressure, which might occur
for example during insertion in wet clayey soils or during refilling
and reassembling, will destroy the pressure sensor!
Electronic installation: Any electrical installations should only be
executed by qualified personnel.
Ceramic cup: Do not touch the cup with your fingers. Grease,
sweat or soap residues will influence the ceramic's hydrophilic
performance.
Do not twist the T5 shaft against the sensor body!

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1.2 Content of delivery
The delivery of a T5 or T5x includes:
Tensiometer, calibrated and filled, with 4-pin plug M12/IP67, with
plug cap
This manual
Rubber protection cap, filled with water to the half, for keeping
the ceramic moist and clean
For available accessories see chapter “Accessories”.
The delivery of a T5-set or T5x-set includes:
Blue plastic transport case
Tensiometer, filled and calibrated, with 4-pin plug M12/IP67,
plug with protective cap
This manual
Rubber protection cap, filled to the half with water to keep
the cup wet and clean
Pack of paper tissues
Polyethylene bottle with 250 ml of water
Filling tube for shafts longer than 10 cm
Evacuation syringe with acrylic adapter for T5 sensor body
Evacuation syringe for T5 shaft
Water reservoir syringe for T5 shaft
Syringe with pipette tip
Spare pipette tip
Gouge auger, diameter 5 mm, length 200 mm
Sensor body auger, diameter 18 mm, length 200 mm
Connecting cable; 1,5 m length

Introduction
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1.3 Foreword
Measuring systems must be reliable and durable and should require
a minimum of maintenance to achieve target-oriented results and
keep the servicing low. Moreover, the success of any technical
system is directly depending on a correct operation.
At the beginning of a measuring task or research project the target,
all effective values and the surrounding conditions must be defined.
This leads to the demands for the scientific and technical project
management which describes all quality related processes and
decides on the used methods, the technical and measurement tools,
the verification of the results and the modelling.
The continuously optimized correlation of all segments and it's
quality assurance are finally decisive for the success of a project.
So please do not hesitate to contact us for further support and
information. We wish you good success with your projects.
Yours,
Georg von Unold
1.4 Guarantee
UMS gives a guarantee of 12 months against defects in manufacture
or materials used. The guarantee does not cover damage through
misuse or inexpert servicing or circumstances beyond our control.
The guarantee includes substitution or repair and package but
excludes shipping expenses. Please contact UMS or our
representative before returning equipment. Place of fulfilment is
Munich, Gmunder Str. 37!
1.5 Durability
The nominal lifespan for outdoor usage is 10 years, but protection
against UV-radiation and frost as well as proper and careful usage
extends the lifespan.

Introduction
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1.6 Tensiometer T5 and T5x
1.6.1 Soils and soil water
All water movements in soils are directly depending on the soil water
tension as water - in soils as well as on the surface - always will
move from a point of higher potential to a point of lower potential.
The majority of soil water flows take place at small water tensions.
Only Tensiometers allow the direct and precise measurement of
these small tensions.
Naturally embedded soils are heterogeneous. Not only precipitation
and evaporation effect the processes, but also texture, particle size
distribution, cracks, compaction, roots and cavities. Due to these
heterogeneities the soil water tension varies. Thus, it is reasonable
to have multiple measuring points at least in soil horizons close to
the surface.
1.6.2 Intended use
The intended use of Tensiometers is the measurement of soil water
tension respectively of matrix potential. These Tensiometers work
from +100 kPa (water pressure/level) to -85 kPa (suction/soil water
tension), the T5x even to a lower tension.
If the soil dries out the Tensiometer runs empty and must be refilled
as soon as the soil is sufficiently moist again.
Soil water and Tensiometer water have contact through the ceramic
which is porous and permeable to water. A wetted porous ceramic
creates an ideal pore/water interface. The soil water tension is
directly conducted to the pressure transducer which offers a
continuous signal.
The atmospheric reference pressure is provided through a
membrane on the cable, a distinctive patented method.
The T5 Miniature Tensiometer is specially designed for punctual
measurements, e. g. in soil columns, pots or laboratory lysimeters, or
when the measurement of a minimal span is desired.
With an active surface of only 0,5 cm2and a diameter of 5 mm the
ceramic tip has all advantages of small dimensions: little soil
disturbance, punctual pick-up and fast response.

Introduction
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1.6.3 Typical applications
Typical applications of the T5 and T5x:
Punctual measurement of water potential
Miniature soil column studies, e. g. in combination with micro
water samplers and soil temperature probes
Determination of pF/wc and K/Psi in soil columns, soil cores
or soil sampling rings
Determination of leachate and capillary water movements
Controlling irrigation
Pot experiments
Measurements in the upper soil horizons in the field
Monitoring with data loggers
Spot readings with the INFIELD7
For in the field applications it might be recommendable to use T4,
T4e or T8 Tensiometers.
1.6.4 Extended measuring range of the T5x
The special version T5x is tested to reach a measuring range of
-160 kPa when delivered. To achieve this, the T5x requires an
absolutely bubble free filling.
You might notice that your T5x might even go down to -250 kPa
before running empty, sometimes even to -450 kPa, but this is an
exception and cannot be guaranteed.
The T5x is identical with the T5 but has a different ceramic. The
extended measuring range is made possible by the effect called
boiling retardation, the special ceramic with smaller pores and, as a
necessary condition, an absolutely gas free filling.
Do not allow the T5x ceramic to dry out by leaving it unprotected
in air: by drying out the tension might reach the destructive
pressure.
Due to the finer pores of the ceramic the water conductivity is
lower. Therefore the response of a T5x is slower than with a
standard T5.
When the shaft is touched it might warm up. This might cause a
short time change of the pressure.

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1.6.5 Specific notes
T5 and T5x are not suitable for dry soils and they are not frost
resistant.
When installed in the field provide sufficient protection.
The less air is inside the cup and the better the soil's conductivity
is, the faster the Tensiometer will respond to tension changes.
It does not make sense to refill a Tensiometer as long as the soil
is dryer than -90 kPa (T5) or - 160 kPa (T5x).
Using a quartz clay slurry is only recommendable in clayey soils
and only if the drilled diameter is larger than the shaft diameter
(5 mm). In coarse sand or gravel soil a fine grained slurry paste
would act as a water reservoir which would lead to a slower
response.
The T5 can be installed in any position and orientation. Bubbles
are easily detectable through the transparent shaft.
Output signals are standardized.

Introduction
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1.7 Quick installation guide
This chapter is only a summary of following chapters. Please read
the complete manual carefully before using the instrument.
T5 are filled and degassed when supplied and are ready for
installation. The procedure is the same for T5 and T5x.
In very soft soils the T5 can be inserted directly without drilling a
hole. As the shaft is fragile, no force should be applied.
For hard soils a special auger kit for is available as an accessory
(art. no. TBT5; included in the T5-set). When the T5 auger is used,
slurrying is unnecessary.
Installation procedure:
1. Drill a hole with the required diameter and depth. Mark the
installation depth on both auger and T5 shaft.
2. Connect the T5 to a readout device, for example a data logger for
continuous measurements or the INFIELD7 handheld device for spot
readings.
During the installation the Tensiometer reading has to be
controlled at any time. Especially in wet, clayey soils a high
pressure might develop while inserting the T5. A pressure of over
3 bar will destroy the pressure transducer. Stop or slow down the
insertion to allow pressure relieve.
3. Carefully remove the water filled rubber cover from the tip and
gently and steadily insert the T5 down to the mark.
Never turn the T5 inside the borehole as this might loosen the
shaft.
Put the protection cup on the plug whenever the plug is not
connected. Dirt will reduce the water tightness of the plug.
Remember to put the protective cap back on the plug after taking
spot readings with the INFIELD7.

Introduction
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Reference air pressure
The reference atmospheric air
pressure is conducted to the
pressure transducer via the air
permeable (white) Teflon
membrane and through the
cable.
Sealed cable
The T5 can be completely buried
if required. If buried cables
should be protected
Sensor body
The incorporated piezoelectric
pressure sensor measures the
soil water tension against
atmospheric pressure.
Acrylic glass shaft
Shafts are available with
lengths from 2 to 20 cm
High grade porous ceramic cup
Filled with degassed water.

Sensor description
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2 Sensor description
2.1 Design
2.1.1 Body and shaft
The sensor body is made of acrylic glass and incorporates the
pressure transducer and all electronic parts. The corpus is backfilled
with resin to hermetically seal the electronics and make the body
watertight.
2.1.2 Pressure transducer
The piezoelectric pressure sensor measures the soil water tension
against the atmospheric pressure. The atmospheric pressure is
conducted through a watertight diaphragm (the white, 2 cm long tube
on the cable) and through the cable to the reference side of the
pressure sensor.
The non destructive maximum pressure is 3 bar (300 kPa).
Higher pressure will damage the sensor and absolutely must be
avoided! High pressures can appear for example when cup and
sensor are reassembled, when inserted in wet, clayey soils or in
tri-axial vessels.
2.1.3 Reference air pressure
The reference atmospheric air pressure is conducted to the pressure
transducer via the air permeable (white) Teflon membrane and
through the cable. The membrane does not absorb water. Water will
not pass through the membrane into the cable, but moisture inside
the cable will leave the cable through the membrane.
The white membrane on the cable must always have contact to air
during a measurement and should never be submersed into water.

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2.1.4 The ceramic tip
To transfer the soil water tension as a negative pressure into the
Tensiometer, a semi-permeable diaphragm is required. This must
have good mechanical stability and water-permeability, but also have
gas impermeability.
The Tensiometer cup consists of porous ceramic Al2O3 sinter
material. The special manufacturing process guarantees
homogeneous porosity with good water conductivity and very high
firmness. Compared to conventional porous ceramic the cup is much
more durable.
The bubble point of a T5 cup is about 200 kPa, of a T5x about 500
kPa. If the soil gets dryer than this air passes through so the
negative pressure inside the cup decreases and the readings go
down to 0 kPa.
With these characteristics this material has outstanding suitability to
work as the semi permeable diaphragm for Tensiometers.
Ceramic cup: Do not touch the cup with your fingers. Grease,
sweat or soap residues will influence the ceramic's hydrophilic
performance.
Do not allow the T5 ceramic to dry out by leaving it unprotected in
air: By drying out the bubble point might be reached, the reading
will go to 0 kPa and air might enter the cup which requires a
refilling.
2.2 Analog output signals
The pressure transducer offers the soil water tension as a linear
output signal, with 1 mV corresponding to 1 kPa.
As the pressure transducer is a Wheatstone full bridge, it has to be
connected in a certain mode. Please read chapter 3.5.3 and the
manual of your display unit or data-logger before connection.

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3 Installation
3.1 Scientific measure ideas
3.1.1 Selecting the measuring site
The installation spot should be representative for the soil which
should be surveyed. For selection it might be necessary to take soil
samples. If the column is refilled care should be taken to achieve the
best possible homogenous distribution and evenly compaction. Bear
in mind a possible shrinking of backfilled columns when T5 are
installed through the cylinder.
On tillage sites (with plants) root spreading and growth during the
measuring period should be considered. Fine roots might develop
around the ceramic cup as it is a poor but assured water source.
Avoid the root zone if possible or replace the Tensiometer from time
to time.
3.1.2 Number of Tensiometers per level
The lower the level the less the variations of water potentials are. In
sandy or pebbly profundities one Tensiometer per depth is sufficient.
Close to the surface about 3 Tensiometers per level are
recommendable.
Guiding principle: More heterogeneous sites and soil structures
require a higher number of Tensiometers.
3.1.3 Extension of the site
Large distance along with high equidistance between the measuring
spots will reduce the influence of sectional heterogeneity.
To determine the water flow according to Darcy two Tensiometers
per horizon or required, one each in an upper and lower level of this
horizon.
Max. recommendable cable lengths for T5 and T5x are 20 meters:
Accuracy: long cables cause a reduction of the accuracy.
Lightning: cables act as antennas and should always be as short
as possible.

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3.1.4 Ideal conditions for installation
For the installation of Tensiometers, the ideal conditions are:
Frost-free soil.
Wet coarse clay or loess.
Low skeletal structure (gravel).
3.1.5 Documentation
For every measuring spot you should:
measure the installation spot from 2 reference points (A must for
installations below the ground surface).
Take documenting photos before, during and after installation.
Save a soil sample.
Write down installation depth and angle with each sensor
identification (serial number).
Mark all connecting cables with the corresponding sensor
identification, serial number or logger channel on each end. Clip-
on number rings are available as an accessory.
3.1.6 Selecting the installation angle
An installation position would be ideal if the typical water flow is not
disturbed by the Tensiometer. No preferential water flow along the
shaft should be created.
If the ceramic cup is positioned higher than the sensor body the first
bubble that may appear inside the shaft will block the water
exchange and stop the Tensiometer to measure.

Installation
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3.2 Installation procedure
The following tools are required for installation in the field:
An auger with diameter 5 mm, preferably the UMS
Tensiometer auger kit TBT5
Rule, spirit level, angle gauge, marker pen
Minute book and camera for documentation of site and soil
profile
Perhaps PE-plastic bags for taking soil samples from the site
1. Drill a hole with the required diameter and depth. Mark the
installation depth on both auger and T5 shaft.
2. If the hole’s diameter is larger than 5 mm mix a paste of water
and grinded soil material.
3. Connect the T5 to a readout device, for example a data logger
for continuous measurements or the INFIELD7 handheld device
for spot readings.
During the installation the Tensiometer reading has to be
controlled at any time. Especially in wet, clayey soils a high
pressure might develop while inserting the T5. A pressure of over
2 bar will destroy the pressure transducer. Stop or slow down the
insertion to allow pressure relieve.
4. If you use a slurry paste pour it into the hole.
5. Pull off the water filled rubber cap from the shaft. Do not turn the
cap as this might unscrew the shaft.
6. Gently and steadily insert the T5 down to the mark while
checking the reading.
Never turn the T5 inside the borehole as this might loosen the
shaft.
The less air is inside the cup and the better the soil's conductivity
is, the faster the Tensiometer will respond to tension changes.
7. Put the protection cup on the plug whenever the plug is not
connected. Dirt will reduce the water tightness of the plug.
Remember to put the protective cap back on the plug after taking
spot readings with the INFIELD7.

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8. Connect the signal cables as described in the chapter
"Connecting the T5 or T5x".
9. Write down the serial number, position, installation angle and
depth.
10. Protect the cables against rodent bites. Lead the cables through
plastic pipes or use the plastic protection tubes which are
available as an accessory.
3.3 Offset correction for non horizontal installations
The pressure transducer is calibrated without
a cup. Thus, no compensation is required for
horizontal installations.
If a T5 or T5x is installed in a non horizontal
position, the vertical water column draws on
the pressure sensor and causes an offset
shift.
Compensate the offset:
by calculation,
by entering the installation angle in the Infield7 for spot readings,
in the configuration of a data logger by setting an offset.
The deviation is largest for a vertical water column (at 0o). The water
column drawing on the pressure transducer is equal to the shaft
length, ranging from 2 to 20 cm. The offset is shifted for 0,1 kPa per
cm shaft length.
Example: A 5 cm vertical column of water below the pressure
sensor will create an 0.5 kPa offset. This means that when the soil
water tension is 0 kPa the sensor will indicate -0.5 kPa.
(1 cm water column corresponds to a pressure of -0,983 hPa.)
3 mm Centre of
p
ressure transduce
r
Centre of ceramic

Installation
3.4 Connecting T5 and T5x
3.4.1 Spot readings with the INFIELD7
T5 and T5x are fitted with a 4-pin plug. The plug can be connected
directly to an INFIELD7 handheld measuring device for taking spot
readings of the soil water tension. The INFIELD7 displays and stores
the soil water tension readings. Stored readings can be downloaded
with the USB converters tL-8/USB or tL-8/USB-Mini which are
available as accessory.
Remember to put the protective cap back on the plug after taking
spot readings with the INFIELD7.
3.4.2 Cables
Connecting and extension cables are required for connecting T5 and
T5x to a data logger or other data acquisition device. Find cables in
the chapter “Accessories”.
Cover plugs with the supplied protective cap if not connected.
3.4.3 General requirements
The pressure transducer is a non-amplified bridge circuit which is
calibrated for 10.6 VDC and requires a stabilized power supply.
Other supply voltages are possible, but the output signal range has
to be recalculated.
In a full-bridge the signal must be measured differentially. This
means do not measure only signal plus against common ground, but
measure the voltage drop between signal minus against common
ground and signal plus against common ground.
The supply voltage has to be constant and stabilized.
The supply voltage must not exceed 18 VDC.
If the Tensiometer is not permanently powered the warm-up
before a measurement should be at least 10 seconds. The 99%
value is reached after 1/100 seconds.
If the Tensiometer is supplied with 10.6 VDC the output signal
range is around 5.3 VDC. A data logger must have the capability
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to measure such a signal level, but many loggers cannot do this.
In this case use a TV-batt power supply.
3.4.4 TV-batt Tensiometer power supply
The TV-batt power supply is specially designed for Tensiometers T3,
T4, T4e and T5. It offers a stabilized 10,6 V power supply, but with
supply minus = -5 V and supply plus = +5,6 V. Therefore the output
signal will have a logger specific signal level. The Tensiometer
signals are in a range of <1 V.
The TV-batt is directly supplied by battery or 12 V mains power.
3.4.5 Connection to a data logger
Some logger types can measure bridge circuits directly, other
loggers require certain measures as the Tensiometer signal minus
and the supply minus do not have the same ground.
3.4.6 Tensiometer loggers DL6-te or GP1-te
T5 and T5x can be connected directly and without further power
supply to the special Tensiometer loggers DL6-te or GP1-te.
The DL6-te is a stand-alone 6-channel logger with six 4-pin sockets.
All Tensiometer with 4-pin plug are connected to the DL6-te with
extension cables EC-4/...
The GP1-te is a stand-alone 2-channel logger with cable glands. All
Tensiometer with 4-pin plug are connected to the GP1-te with
connection cables CC-4/...

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4 Service and maintenance
4.1 Refilling
To assure a rapid and reliable measurement of the soil water
tension, the cup must be filled possibly bubble-free with degassed
water. After dry periods or periods with a large number of wet and
drying out successions, Tensiometers must be refilled.
Refilling is the easiest with the refilling tools included in the T5-set or
T5-case. A readout device, for example the INFIELD7, is always
needed to control the signal.
4.1.1 When do Tensiometers need to be refilled?
Tensiometers need to be refilled:
the curve of the readings apparently gets flatter (for example a
rain event has no sharp peak but is round),
the maximum of -85 kPa is not reached anymore.
Refilling is only reasonable if the soil is moister than -90 kPa.
If the soil gets dryer than -85 kPa, the readings will remain constant
at the vapour pressure of water (i. e. for example 92,7 kPa at 20°C
and atmospheric pressure of 95 kPa). By diffusion and slight leakage
the reading will slowly drop within months.
If the soil dries out and reaches the bubble point (-200 kPa for T5;
-500 kPa forT5x), the tension will decrease rapidly as air will enter
the cup.
4.1.2 Refilling T5 in lab and field
This chapter describes the refilling of T5 or T5x using the T5-set.
The procedure has 5 steps:
1. Check the T5 Tensiometer
2. Degas cup and shaft
3. Degas sensor
4. Reassemble