UMS HYPROP Operation Manual

Operation Manual

HYPROP

This manual is also available in German:

http://www.ums-muc.de/static/Bedienungsanleitung_HYPROP-VIEW.pdf

At a glance – how it works

Evaporation

Soil sample

Sampling ring

Balance

Tensio Top

Tensio Bottom

to USB
interface

Pressure sensors

Sensor unit

HYPROP

®

is a fully automated measuring and evaluation system to
determine the hydraulic properties of soil samples. HYPROP measures
the water tension at two levels of a sample using two tensio shafts. If the
conductivity of the sample is poor the soil in the upper horizons dries
out whereas the lower horizons are still humid. So the upper tensio shaft
measures much drier tensions than the lower one which is still humid. If the
conductivity is good water is evaporated out of the whole sample and
both tensions are almost identical. The water content for the pF/WC curve
is calculated based on the weight loss of the sample.

This measuring concept is based on Schindler’s method. Please find further
information in the chapter “Theory”.

Legend

water electronics soil

water vapor ceramic all other parts cross section of a part

Parts of the device
and scope of delivery

sample ring

sensor unit

O-ring (red)

for sealing the tensio shafts

to the pressure sensor

ceramic

shaft

silicone gasket

tensio shafts

O-ring (black)

for dirt protection

balance

Note

This manual does not describe the evaluation of the measuring data using the HYPROP-FIT
software. For this please find another manual:

http://www.ums-muc.de/static/Manual_HYPROP-FIT.pdf

Additional parts
in the scope of delivery

sensor unit

O-rings

tensio shafts

50 mm and 25 mm

HYPROP

connecting cable

plastic caps silicone gasket and

nonwoven cloths

tensioLink

®

T-piece

refilling attachment

for sensor unit

saturation plate

5 | Scope of delivery

droplet syringe

tensio shaft auger tube for vacuum syringe

and attachment for sensor unit

vacuum syringe reservoir syringe

6 | Scope of delivery

auger guide

sample ring 250 ml

with plastic caps

deionized water power device

HYPROP USB adapter

7 | Scope of delivery

8 | Content

Contents

At a glance – how it works ................................................................................... 2

Parts of the device and scope of delivery .......................................................... 3

Important information ......................................................................................... 10

Safety instructions ............................................................................................10

Intended use ....................................................................................................10

Warranty ...........................................................................................................10

HYPROP-VIEW software functions ....................................................................... 11

Key functions ....................................................................................................11

User support .....................................................................................................11

Show devices ...................................................................................................12

Device tree ......................................................................................................13

Initial operation .................................................................................................... 16

Software installation: HYPROP-VIEW and HYPROP-FIT .................................16

Hardware configuration ..................................................................................17

How to use the tube connections . ................................................................18

General measuring procedure .......................................................................... 19

Preparing the measurement .............................................................................. 20

Saturating the soil sample ..............................................................................20

Filing the device ..............................................................................................22

using the Refill Unit (accessories) ..........................................................23

using syringes ...........................................................................................28

Offset recalibration ..........................................................................................41

Implementing the tensio shafts in the sensor unit ........................................43

Attaching the dirt protection .........................................................................46

Function check ................................................................................................47

Assembling the sensor unit and the soil sample ..........................................49

Connecting the sensor unit and the balance .............................................51

Preparing the balance ...................................................................................53

Adjusting ............................................................................................................55

Default settings .................................................................................................57

Measuring ............................................................................................................ 58

Multi balance mode (one balance per sensor unit) ..................................58

Single balance mode (one balance for more sensor units) ......................59

Optimal measuring curve ................................................................................... 61

Notes on suboptimal measuring curves .......................................................63

Finishing a measurement .................................................................................... 64

Determining the dry weight ................................................................................ 67

Weighing the dry mass ....................................................................................68

Evaluating the measurement ............................................................................. 69

Trouble shooting .................................................................................................. 70

Cleaning and maintenance ............................................................................... 71

Cleaning the sensor unit .................................................................................71

Changing the O-rings in the sensor unit .......................................................72

Storage .............................................................................................................73

Additional accessories ....................................................................................... 74

Theory ................................................................................................................... 76

Preliminary note ...............................................................................................76

Measuring method ..........................................................................................77

Explanation of terms ........................................................................................78

Generating data points ..................................................................................80

Additional notes ..............................................................................................82

Addendum ........................................................................................................... 83

Typical measuring curves ...............................................................................83

Standard pF curves .........................................................................................90

Procedure of sampling for WP4 measurements

after a HYPROP measurement .......................................................................91

Units for soil water and matrix potentials ......................................................91

Facts and figures ................................................................................................. 93

Technical data ................................................................................................93

Literature cited ..................................................................................................... 94

9 | Content

Important information

10 | Important information

Electrical installations must meet the safety and EMC requirements of the
country in which the system is used. Damages caused by the user are not
covered by the warranty. HYPROP is a device to measure soil tensions as well
as soil water pressures and temperatures and is only intended for this parti­cular use. Please keep the following notes in mind:

Note

Please do not touch the ceramic of the tensio shafts with bare fingers. Grease or soap
reduces the hydrophilic characteristics of the ceramic.

Note

Do not stick sharp objects into the holes of the sensor unit. You may damage the
pressure sensor.

Intended use

Safety instructions

Warranty

HYPROP® is a measuring system that is intended to be used for measuring the
water retention function and the hydraulic conductivity as a function of the
water tension or the water content of soil samples.

UMS offers a warranty for material and production defects for this device in
accordance with the locally applicable legal provisions, but for a minimum
of 12 months. The warranty does not cover damage caused by misuse, inex­pert servicing or circumstances beyond our control. The warranty includes
replacement or repair and packing but excludes shipping expenses. Please
contact UMS or our representative before returning equipment. Place of ful­fillment is Gmunder Str. 37, Munich, Germany.

Software functions

The key functions are:

• displaying the connected devices,

• displaying the measurement data

• filling assistant

• measurement configuration wizard

The wizard is explained in the respective chapter.

User support

Key functions

Example of user support: Help Function

Note

After starting the software the user support leads you through all software functions.
If you are an experienced user you may not like to use the wizard of the measuring
configuration and enter the data directly instead. This is possible too.

When you start the software and the help
function is activated notes of the next
step are displayed, e.g. here you are
asked to click on the “Show device” icon.

11 | Software functions

Show connected devices

Click on an icon in the upper screen bar
e.g. “Measurement”.

Click on the icon “Show devices”.

In case a balance does not show, check
if the balance is switched on.

Follow the wizard.

When all steps are done, click on “Apply”
if you want to enter the configuration.
If you click on “Cancel” you return to the
initial page, where you have opened the
wizard.

Data you have entered are set in the
program.

All connected balances and sensor
units are displayed.

Example of user support: Wizard

12 | Software functions

The device tree (example)

Sensor unit “soil lab 18” is connected to
the computer via a HYPROP balance.

Sensor unit “soil lab 15” is connected
to the computer via the USB adapter.

A Kern balance is connected to
the computer via a RS232 interface.

Sensor unit “soil lab 17” is connected to
the computer via a HYPROP USB Cable.

13 | Software functions

Main window with manager

Mode (one or
more balances)

Connected
devices

One measurement
file per soil sample is
generated

Data to be typed
in by the user

Device ID
(click right mouse
button to change)

Short cuts to
key functions

Unit Link to the HYPROP-FIT

software

Next step

Switches to displaying
the measurement
values when a mea­surement is running

Default folder for
measurement files

Interrupt, stop or start
all measurements

14 | Software functions

Main window with measurement values

Stops the
measurement

Runs an immediate
measurement

Display of the soil sample’s
tensions and weights over
time (graphical)

Display of the soil sample’s
tensions and weights over
time (tabular)

Opens the measurement
file in HYPROP-FIT when
the measurement
is running

Deletes all measurements
performed

15 | Software functions

Initial operation

Put the CD with the HYPROP software into
the computer. If you do not have a CD
download the software using the link

http://www.ums-muc.de/static/
HYPROP-VIEW.zip

http://www.ums-muc.de/static/
HYPROP-FIT.zip.

Double click on Setup.exe

Follow the wizard.

Connect the HYPROP balance
to the USB port.

Start the HYPROP software.

The wizard leads you through the
installation.

The balance connects automatically
to the computer.

Your HYPROP is ready to measure.

Note

For installing the HYPROP software you may need administrator rights.

Software installation: HYPROP-VIEW and HYPROP-FIT.

16 | Initial operation

Hardware configuration

Change device ID

Each sensor unit needs its particular device ID otherwise a communication
collision may occur.

Click on device with right mouse button.

Click on “apply”.

Choose “Chance Device ID”.

Choose an available ID from the
pulldown menu.

Click on device with right mouse button.
Choose “Rename”.

Click on “apply”.

Change device name (optional)

17 | Initial operation

Note

Cut the tube always rectangular otherwise the connection will be leaking.

To connect the tube to the fitting push the tube in as far as it will go.

To remove the tube press blue ring and pull.

How to use the tube connections

18 | Initial operation

General measuring procedure

A measurement consists of the following steps:

• soil sampling and preparation

• saturating the soil sample

• preparing the measuring system

• setting up the sample in the measuring system

and starting the measuring campaign

• evaluating the measuring results with HYPROP-FIT.

In the following this manual will guide you through the measuring
process step-by-step.

19 | General measuring procedure

Take the sample ring with soil out of the
transport box and clean it. Prepare top
and bottom side of the sample (e. g. with
a saw blade).

Put a plastic cap upside down on the
sample ring – on the side where the ring
has the cutting edge. The cap works
as a support. This makes sure that no
soil gets lost even when loose sand is
in the sample ring.

Preparing the measurement

Saturating the soil sample

20 | Preparing the measurement

Turn soil sample upside down and put it
on a table. Remove cap on top, place
nonwoven cloth on the soil and put the
filling bowl on the sample ring.

Turn soil sample again upside down.

Note: Recommended time for saturation

Material Refilling after Aufgesättigt nach

Coarse sands about 9 min about 10 min

Fine sands about 45 min about 1 h

Silts about 6 h about 24 h

Clay n. a. up to 2 weeks

Raise the water level up to 5 mm below
the sample rim (recommended times
see below). Do not pour water on the
sample – you may trap air. Use the time
table below as a reference to determine
how long samples take to saturate.

Fill 2 cm (1 in) of degassed water into a
tray. Put the soil sample into the tray – tilt
it so that air under the soil can escape.

Let soil sample capillary saturate until the
surface is shining.

Put a plastic cap upside down on the
sample ring. Do not fix it so that air can
ventilate. The cap protects the soil from
sun radiation and evaporation.

21 | Preparing the measurement

Filling the device

The tensio shafts “transduce” the matrix potentials (also called tensions) of the
soil sample through their porous ceramic tip and the water filled shaft to the
pressure sensors in the sensor unit. I.e. the tensio shafts provide via their pores
a capillary contact between the water in the tensio shaft and the soil water.

To make sure the pressure is “transduced” precisely no air must be contained
(dissolved or solved) in the water. That is why the tensio shafts and the sensor
unit need to be degassed completely.

For degassing the water you can use two different methods:

1. by means of the Refill Unit (accessory) makes all necessary

steps simple and is fast.

2. by means of syringes (basic scope of delivery) takes some

more time and needs more manual work.

In the following either method is described in detail.

22 | Preparing the measurement

Degassing the device using the HYPROP Refill Unit

High performance vacuum

pump enables generating

a vacuum value that is only

8 hPa (0.8 kPa)

Scope:

Vacuum mount (including

manometer and vacuum

flask, to avoid water entry

into the pump)

Manometer

Beaker mount with

2 beakers. Up to 10

beaker mounts can

be connected in series.

End fitting

with valve

23 | Preparing the measurement

Connect the devices of the Refill Unit
as shown. Tubes and fittings that need
to be connected are indicated by the
same color.

Put the vacuum pump on the ground
(lower temperature) to gain better
vacuum values.

Connect the unit to a timer and the timer
to the mains

Note

We recommend to use a timer as this increases the pump life, reduces energy consumption
and air bubbles that may be there are ripped off when the pump starts. The timer is not in
the scope of delivery as the electrical requirements vary from country to country.

We also recommend with every degassing procedure to degas an additional bottle of
deionized water. You will need the water when you fill the tensio shafts.

Note

Do not touch the ceramic of the tensio shafts with bare fingers. Grease
or soap reduces the hydrophilic characteristics of the ceramic.

The water in the tensio shaft evaporates to the ambient air. Therefore
cover the tensio shaft tip with a silicone cap.

24 | Preparing the measurement

Fill holes of the sensor unit bubble free.
For this use the droplet syringe.

Set up refilling attachment and fix it.
Fill attachment with droplet syringe –
ideally bubble free.

Filling the sensor unit

Note

Do not stick the syringe tip into the holes of the sensor unit. You may damage the
pressure sensor.

25 | Preparing the measurement

Timer starts the pump automatically and
works in the rhythm set. The water in the
tensio shafts is degassed after minimum 24
h running time.

Screw 1, 2, 3 or 4 tensio shafts into the
adapters.

Put blind plugs on connections not used.

Close valve of the beaker unit.

Fill beaker(s) with deionized water.

Set timer according to a rhythm of
e.g. 5 min “on” and 55 min “off”.

valve

Note

If the manometer of the vacuum mount drops rapidly the system is leaking. Please check,
fix leakage and restart degassing procedure. If you use another pump than the HYPROP
pump, make sure that it is able to provide a vacuum value that is 8 hPa (0.8 kPa) below
atmospheric air pressure. The power does not matter! Vacuum pumps that reach only a
smaller vacuum value are not suitable.

26 | Preparing the measurement

Turn pump off. Open valve slowly and
cautiously.

When the water in the tensio shafts and
the sensor unit has been degassed
you can continue to set up the HYPROP
(see chapter “Implementing the tensio
shafts into the sensor unit”).

Bringing the HYPROP Refill Unit back to ambient pressure

Note

Never remove a tube in order to ventilate the system. The sudden pressure shock will
damage the pressure sensors in the sensor unit.

27 | Preparing the measurement

If you have time put the tensio shafts
in deionized water over night.
Then the degassing takes less time.
No water must enter the shaft from
above, otherwise air will be locked
in the pores.

Note

Do not touch the ceramic of the tensio shafts with bare fingers. Grease
or soap reduces the hydrophilic characteristics of the ceramic.

The water in the tensio shaft evaporates to the ambient air.
Therefore cover the tensio shaft tip with a silicone cap.

Degassing the device using syringes

1,5 cm

28 | Preparing the measurement



Fill reservoir syringe with 10 ml

deionized water.

Turn syringe upside down and
remove residual air.



Close reservoir syringe tightly with

your finger, pull plunger completely
and hold it.

The vacuum in the syringe degasses
the water. Air bubbles show.

Filling the tensio shafts

29 | Preparing the measurement



Toss and turn reservoir syringe to

“catch” air bubbles.

30 | Preparing the measurement



Turn syringe upside down and

remove residual air.

Push tube piece onto the tip of the syringe.

Push plunger of the syringe until a menis­cus builds up on the tube piece.

Push the ceramic of the first tensio shaft
into the tube piece.

Repeat step  to  until air bubbles
do no show anymore.

31 | Preparing the measurement

Fill vacuum syringe with 5 ml deionized
water. Turn syringe upside down and
remove residual air.

Degas water in the vacuum syringe –
analogous to degassing the reservoir
syringe.

Push tube piece over the tip of the syringe.

Push plunger of the syringe until a meniscus
builds up on the tube piece.

32 | Preparing the measurement

Connect the two syringes and the tensio
shaft.

The two O-rings help seal the tubes
against the tensio shaft shaft.



Pull out the plunger of the

vacuum syringe …



33 | Preparing the measurement

… until the plunger stoppers snap in.
The vacuum in the syringe removes
the air from the tensio shaft.



Hold plunger and syringe, press in

the plunger stoppers and let the
plunger slowly move forward.



plunger stoppers plunger stoppers

34 | Preparing the measurement



Remove syringe, turn it upside

down and remove residual air.





Push vacuum syringe bubble free

onto the tensio shaft shaft again.

Degas water in the second tensio shaft.

For this repeat step



to  until air

bubbles do not show anymore.

35 | Preparing the measurement

Fill holes of the sensor unit bubble free
with deionized water. Use droplet syringe.

Filling the sensor unit

Note

Do not stick the syringe tip into the holes of the sensor unit. You may damage the
pressure sensor.

Set up refilling attachment and fix it.
Fill attachment with droplet syringe –
ideally bubble free.

36 | Preparing the measurement



Push blue tube piece onto the

vacuum syringe and fill the tube.



Fill vacuum syringe with 15 to 20 ml deio­nized water. Degas water in the syringe
as explained on the previous pages.



Connect blue tube onto to the fitting

of the refilling attachment.



Pull out the plunger of the vacuum

syringe until the plunger stoppers
snap in.

The vacuum in the syringe removes the air
from the sensor unit and its attachment.
Air bubbles show.





Note

Be extremely cautious! Do not let the plunger of the syringe shoot down as the pressure
shock will damage the pressure sensor.

37 | Preparing the measurement



Let the air bubbles rise up into the

tube by cautiously knocking and
shifting the sensor unit.



Note

In no case push the sensor unit on a
hard surface! The impact will cause
pressure shocks that damage the
pressure sensors.

38 | Preparing the measurement



To relieve pressure hold plunger

and syringe, press in the plunger
stoppers and let the plunger
slowly move forward.



Remove syringe from the tube,

turn it upside down and remove
residual air.

Repeat steps  to  until air bubbles
do not show anymore.

Note

Be extremely cautious! Do not let the plunger of the syringe shoot down as the pressure
shock will damage the pressure sensor.



39 | Preparing the measurement

Push vacuum syringe filled with degassed
water into the tube on the refilling
attachment. Pull plunger until the
plunger stoppers snap in. The pressure
shown on the screen must reach a
vacuum value equal to the atmospheric
air pressure minus 20 hPa (2 kPa).

If this value can be reached the sensor unit
is ready to measure after about 3 hours.

Note

If the vacuum value does not reach a pressure equal to the atmospheric air pressure minus
20 hPa (2 kPa), then there is most likely:

• a dead volume in the syringe,

• air in the tube

• or a leakage in the system (e.g. between the sensor unit and the attachment)

After you have fixed the problem you need to degas the system again.

40 | Preparing the measurement

41 | Preparing the measurement

Offset recalibration

In the course of time the offsets of the electronic HYPROP sensors may slightly
drift. When you click the function "Offset Recalibration" the device checks
automatically if the offset values are within the narrow range set by UMS. Are
they are out of range the device recommends to run an offset recalibration.

Note

The offset recalibration can be done before every measurement as a routine to prepare
the sensor unit.

Fill and degas sensor unit (please find
description in the previous chapter).

Carefully remove sensor unit adapter, so
that all the water from inside is collected
on the up side of the sensor unit.

Connect sensor unit to the USB adapter.

sensor

unit

Click the "Offset Recalibration" icon.

42 | Preparing the measurement

Select the sensor unit to be recalibrated.

If yes go through the next steps according
to the wizard.

Check if the device recommends
a recalibration.

If not, you can stop the recalibration

by a click on "Close".

Put silicone tube on the ceramic tip of
the tensio shaft. Turn tensio shaft upside
down and fill it with deionized and de­gassed water until a meniscus builds up.

Implementing the tensio shafts in the sensor unit

Note

Fill tensio shaft only with degassed water otherwise air bubbles build up.

The ceramic of the tensio shafts must be kept wet.

For the following steps it is necessary to connect the sensor unit with the computer.
So you can monitor the pressure increase when you screw in the tensio shafts. And make
sure that the pressure sensors will not be damaged.

43 | Preparing the measurement

Click "Set Zero Point" and wait until the
recalibration has been finished.
Close the window by a click on "Close".

Note

For the offset realibration as well as for the following implementation of the tensio shafts please
connect the sensor unit directly to the PC. Do not use the connection balance - sensor unit.

Connect sensor unit to the USB adapter.

Click on the icon “Refilling”.

Follow the wizard.

sensor

unit



Fill deionized water into the silicone

tube piece.



Screw in tensio shaft.



Monitor the tension values on the

screen.



After about 9 turns the O-ring in the

sensor unit starts sealing and the
pressure increases rapidly.



Screw in the tensio shaft by another

quarter of a turn.

44 | Preparing the measurement

Repeat all steps for the second tensio
shaft.

When all steps are done click on “Close”
and you get to the page where you
opened the refilling wizard.

Note

Be extremely cautious when you screw in the tensio shafts filled
with water. The pressure that can damage the pressure
sensor increases abruptly at about 9 turns. This pressure
should not exceed 2000 hPa (200 kPa) – and in no case
3000 hPa (300 kPa).

Note

If you open the wizard during a measurement the measuring process is interrupted.
Therefore the wizard is closed automatically after 2 min and the measurement is continued.

45 | Preparing the measurement

Attaching the dirt protection



Push black O-ring for dirt protection

on the tensio shaft until it sits in the
groove of the sensor unit.



Remove silicone tubes from the

tensio shaft tips.



Put silicone gasket on the sensor unit.



Cover tensio shaft tips again

with silicone tubes and fill them
with deionized water.

Silicone gasket for
dirt protection

O-ring for dirt
protection

O-ring in the
sensor unit
for sealing



Fill the silicone tubes immediately

with deionized water.

 

 







46 | Preparing the measurement

Connect sensor unit to the USB adapter.

Click on the "Refilling" icon.

Function check

sensor

unit

HYPROP USB adapter

Checking the zero point



Put a drop of water on the ceramic

tip of the tensio shaft. By this zero
potential exists.



The screen should indicate zero

pressure for both tensio shafts.





47 | Preparing the measurement



Keep a syringe filled with deionized

water on hand.



Remove silicone tube from the long

tensio shaft and dry the ceramic tip
with a paper towel.



Use a sheet of cardboard and fan air

to the ceramic. Monitor the pressure
display on the screen.

The pressure should increase up to
the atmospheric air pressure minus
100 hPa (10 kPa) within 15 seconds.

Checking the speed of response



As soon as the pressure has reached

the atmospheric air pressure (e.g.
100 hPa or 10 kPa) wet the ceramic
immediately with deionized water.

Otherwise air may enter the tensio
shaft and the degassing process has
to be repeated!



Put silicone tube on tensio shaft and

fill up.

Repeat steps  to  for the short
tensio shaft.

Note

If the pressure does not rise to tensions close to atmospheric air pressure minus 100 hPa
(10 kPa), highly likely air is in the tensio shaft. Then degassing the water in the sensor unit
has to be repeated!
Other potential failures:

• tensio shaft does not sit tightly on the O-ring,

• tensio shaft is clogged (e. g. by oils from fingers)

• O-ring of the tensio shaft is worn out.

Checking the end vacuum

48 | Preparing the measurement

Assembling the sensor unit and the soil sample

Drilling the holes



Set tensio shaft adapter onto the

saturated soil sample in the tray.
The small hole should be above
the sample ring number. This makes
finding the right position easier when
the sensor unit and the soil sample
are assembled.



Use the tensio shaft auger to drill the

holes. Carefully drill in 10 mm steps
and make sure the soil sample is not
compressed.

Fill drill holes with water to make sure air
will not be pressed into the soil sample
during assembly.

Sample
ring
number

Small
hole

49 | Preparing the measurement



Set the sensor unit cautiously upside

down onto the soil sample. Make
sure, no air gaps are generated and
the soil is not compressed.





Turn the whole test assembly

upside down.



Remove saturation plate and

nonwoven cloth.



Fix soil sample with the clips.



Carefully clean the sample ring and

clips and dry them. Otherwise water
and dirt will be weighed too.

The soil sample is now ready to be

measured.

50 | Preparing the measurement

Connecting the sensor unit and the balance

Multi balance mode

(i.e. one balance per sensor unit)

Filling Measuring

USB

USB hub

max. 20 sensor units

sensor

unit

sensor

unit

PC

HYPROP
USB-Adapter

HYPROP balances
(or other balances)

51 | Preparing the measurement

Single balance mode

(i.e. one balance for more sensor units)

Weighing

HYPROP balance
(or other balance)

to power supply

to power supply

USB USB

Filling and measuring

PC

max. 20 sensor units

tensioLINK

®

T-piece

HYPROP
USB adapter

sensor unit

52 | Preparing the measurement

Set-up

Preparing the balance

The balance should be set up on a vibration-free work place that is ideally
used for HYPROP measurements only.

 Set up the balance horizontally.
 Adjust the balance by turning the

balance feet. The air bubble should
be in the center of the level.

 Connect the balance to the power

supply and computer and turn it on.

 Connect the cable of the sensor

unit to the balance and fix it on the
magnet clamp.

 Put the free end of the cable and the

plug on the balance. Push the “Tara”
button and set the display to zero.

Connect the sensor unit and put it on the
balance.













magnet
clamp

53 | Preparing the measurement

Note

The both ends of the sensor unit cable must
not touch each other as this would lead to
noisy measurements.

54 | Preparing the measurement

Adjusting

For precise measurements the balance needs to be adjusted to the local
conditions:

• when it has been set up initially

• after a change of position

• after a temperature change.

We recommend adjusting the balance also every 4 weeks when the balance
is in measuring operation. For its adjustment the balance is equipped with an
adjusting weight.

Remove magneto cable and HYPROP
sensor unit.

Connect balance to the power supply
and turn it on.

Push and hold button until S.A.
CAL appears.

Func

S.A. CAL

Push both buttons at the
same time and release them.

VaIT

CAL. 0

The readout flashes.

CAL

CAL. on

The zero point is saved.

CAL

55 | Preparing the measurement

Turn balance knob to “CAL”.

CAL. on

The readout flashes and the
adjustment runs automatically.

CAL

CAL. oFF

The adjustment is done.

CAL

Turn balance knob to “WEIGH”.

End.

The balance is adjusted and ready to weigh.

buSY

CAL

56 | Preparing the measurement

Note

The weight shown on UMS sample rings refers to g = 9.80665 m/s².

Function

Display Adjustment

Bar graph On

Toleranzwiegung Off

Nullabgleich

Automatic zero point
correction activated.

Automatic shut off after
3 min (recharge able
battery operation)

On

Readout speed medium speed

Vibration filter medium sensitivity

Interface 6 digit data format

1 b.G. 1

2 SEL 0

3 A.0 1

4 A.P. 1

5 rE. 3

6 S.d. 2

7 I.F. 1

Default settings

57 | Preparing the measurement

Multi balance mode

(one balance per sensor unit)

Measuring

Click on the "Show devices" icon.

If the balance does not show on the
screen check if balance is turned on.

Click on the "Measurement wizard" icon.

Push start button.

Enter the following data – either via the
wizard or directly in the manager:

- measuring mode,

- measuring unit,

- name of the soil sample,

- sample ring type and

- balance type.

After entering the data the
key legend changes to “Start”.

Actual and maximum
tension value of the
upper and lower
tensio shaft in minute
cycle)

Actual
sample mass
(in minute cycle)

!

58 | Measuring

Note

The magneto cable from the balance to the magnet clamp must lie freely as a loop
without touching anything.
Before you start weighing wait for at least 5 minutes to let the cable tension release.

Single balance mode

(one balance for more sensor units)

Click on the "Show devices" icon.

Push start button.

After filling in the data the
key legend changes to “Start”.

Actual and maximum tension value
of the upper and lower tensio shaft
(in minute cycle)

!

If the balance does not show on the
screen check if balance is turned on.

Click on the "Measurement wizard" icon.

Enter the following data – either via the
wizard or directly in the manager:

- measuring mode,

- measuring unit,

- name of the soil sample,

- sample ring type and

- balance type.

59 | Measuring

Note

The magneto cable from the balance to the magnet clamp must lie freely as a loop
without touching anything.
Before you start weighing wait for at least 5 minutes to let the cable tension release.

Weighing the sample mass

Remove plug from sensor unit.

Follow the instructions on the screen.

The system identifies automatically the sen­sor unit having been put on the balance.

A menu opens on the screen showing
information about the status and the
weighing routine.

In the single balance mode we recommend to weigh the sample mass
twice a day.

Note

Only one sensor unit may be disconnected. Please do not pull the magneto cable but use
the serrated area of the plug instead.

The number of samples is limited to 20.

Actual sample mass

The menu leads you through the
weighing procedure.

Disconnect sensor unit from the balance
and connect it again to the T-piece of
the tensioLINK

®

. This function is supported

with a menu.

Note

If you run more sensor units with one balance the magneto cable is not needed.

60 | Measuring

Optimal measuring curve

Every measurement runs in 4 phases provided that tensio shafts and sensor
unit are filled air free.

Phase 1, regular measurement range

Tension value curve rises up without flattening until it reaches the boiling point
of the water.

Phase 2, boiling delay phase

In the ideal case – when the system is filled completely air free – the tension
value rises up to the boiling delay area (above the ambient air pressure). This
is nice to have but in general not necessary for the evaluation.

Phase 3, Cavitation phase

Water vapor is generated in the tensio shaft and the tension value drops abruptly
down to the boiling point. After this the tension value decreases only slightly.

Phase 4, Air entry phase

The tension value again drops abruptly – now to zero, as air penetrates the
ceramic. The air entry point is a material characteristic of the ceramic and
amounts to about 8800 hPa (880 kPa). This point can also be used for the
evaluation.

61 | Optimal measuring curve

0

1000

2000

Phase 1 Phase 2 Phase 3 Phase 4

The four phases using one tensio shaft as example

measured values interpolated values

time

tension
[hPa or kPa]

air entry point of the tensio shaft

actual atmospheric air pressure

regular measurement range cavitation air entryboiling

delay

62 | Optimal measuring curve

0

1000

2000

Notes on suboptimal measuring curves

Often the optimal measuring curve up to the boiling delay cannot be achie­ved. The curves then look similar to the example below. But even these cur­ves can be used for an evaluation. In the chapter “Addendum” you find
exemplary measuring curves of various soils.

air entry

Tensio top Tensio bottom

63 | Optimal measuring curve

time

tension
[hPa or kPa]

0

Finishing a measurement

You can finish a measurement in three ways:

1. You stop when the upper tensio shaft has reached the cavitation phase

(see illustration 1). Then you do not use the air entry point.

2. You are willing to use the air entry point. Then there are two possibilities:
a) The air entry point of the first tensio shaft has been reached and the second

tensio shaft is still in the regular measurement range (phase 1) or in boiling
delay (phase 2). In this case HYPROP can calculate the medial value
of the Tensio top and Tensio bottom curve (see illustration 2).

b) When the air entry point of the first tensio shaft has been reached and

the second tensio shaft is still in the cavitation phase (phase3), the medial
value of the two cannot yet be calculated. Then please wait until the air
entry point of the second tensio shaft has been reached (see illustration 3).

StopTensio Top Tensio Bottom

64 | Finishing a measurement

Illustration 1

time

tension
[hPa or kPa]

0

air entry point

StopTensio Top Tensio Bottom

Illustration 2

65 | Finishing a measurement

time

tension
[hPa or kPa]

0

air entry point 1 air entry point 2

StopTensio Top Tensio Bottom

In either case click the
“Stop” button to finish
the measurement.

After this you can have the software HYPROP FIT evaluate the measuring
values. For this please see the manual using this link:

http://www.ums-muc.de/static/Manual_HYPROP-FIT.pdf

Illustration 3

66 | Finishing a measurement

time

tension
[hPa or kPa]

HYPROP needs the dry weight of the soil sample to be able to calculate the
volumetric water content based on the weight reduction. Therefore the sample
has to be weighed after the measuring campaign.

Note

If the soil sticks too tightly to the sensor unit (which is often the case with clayey soils) put the
sample ring with the sensor unit upside down in water. The water level should be above the
rim of the sample ring. If necessary leave it in the water over night. Then the sample ring can
be removed more easily.

Determining the dry weight

Put the soil sample in a bowl (ideally
in a heat resistant one, so that you
can put it in the oven for drying).

Open the clips of the sensor unit.

Cautiously remove the sample ring.
Do not tilt the sample ring. If you do
so you may break the tensio shafts.

Collect the soil material completely in
the bowl.

67 | Determining the dry weight

To determine the real water content of the soil the dry mass is weighed.

Weighing the dry mass

Dry the soil sample in a drying oven at
105° C for 24 h.

Weigh the sample.

Enter the net mass of the dry soil sample in
the HYPROP FIT software using the register
“Evaluation”.

Clean also sample ring and silicone
gasket above the bowl to avoid losses.

68 | Determining the dry weight

Evaluating the measurement

You can have the software HYPROP FIT evaluate the measuring data. The pro­cess runs step by step from “Information” and “Measuring” over “Evaluation”
to “Fitting” and “Export”.

To get an explanation of all the software’s possibilities please use the manual
that you find with the following link:
http://www.ums-muc.de/static/Manual_HYPROP-FIT.pdf

Example: Fitting of
a single measurement

Example: Fitting of
several measurements

69 | Evaluating the measurement

Problem How to solve it

1. The tensio shaft is dry. Fill tensio shaft either by means of a syringe or vacuum pump

with deionized water (see chapter “Preparing a measurement”.

2. You identify bubbles

in the tensio shafts.

Repeat filling. If this does not help: try to detect leakage
(e.g. red O-ring of the tensio shaft) and fix it.

3. The tension value rea-

ches only 500 … 700 hPa
(50 … 70 kPa) and
drops then.

a) Tensio shaft has not been filled air free (how to fix it see above).
b) Red O-ring of the tensio shaft does not seal properly. Check
and if necessary replace O-ring (see chapter “Cleaning and
maintenance”).

4. The Tensio bottom

stops at 200 … 700 hPa
(20 … 70 kPa) and
drops then.

Potential reasons: a) The soil sample is disrupted horizontally
and was initially filled with water but later on with air which
works as a capillary block. b) Same problems as #3.

5. The tension value ex-

ceeds the value of the
atmospheric pressure
(e.g. 1000 hPa or 100 kPa).

This is no fault but the physical effect of boiling delay.
Thus you can measure with HYPROP beyond the “normal”
measuring range.

6. Measuring data are

no longer recorded.

a) Check connection to the USB port.
b) Change energy management of your computer to
“continuous operation” (typical when using a lap top).

7. At the beginning of a

measurement the Ten­sio bottom “overtakes”
the Tensio top

Maybe the tensio shafts have been interchanged. There is no
need to interrupt the measurement as you can correct the mea­suring values in HYPROP-FIT.

8. In the “Single balance

mode” the software
does not find any sensor
units.

Disconnect the sensor units one by one and have the software
show the device tree. Probably one or more sensor units have
the same address. Change addresses (see chapter “Preparing
a measurement”).

9. wYou monitor readout

values of 4000 hPa
(400 kPa).

The pressure sensors have been destroyed. The sensor unit must
be checked. Please send it/them to UMS or your local dealer.
We will repair it fast and at cost-efficiently.

70 | Trouble shooting

Trouble shooting

Cleaning and maintenance

Do not remove the tensio shafts.

Close lid of the plug.

Clean sensor unit properly upside down
under running water.

Dry with cloth.

When the sensor unit is clean unscrew ten­sio shafts by about 5 turns and clean them
again. Then remove tensio shafts.

Cleaning the sensor unit

The sensor unit meets the protection class IP65 and therefore can be cle­aned under running water.

After removing the tensio shafts keep
sensor unit upside down and wash residu­al soil particles away.

Note

Always clean the sensor unit upside down using a wash bottle to make sure no soil particles
enter the sensor unit.

71 | Cleaning and maintenance

When during the tension rise the values of
a tensio shaft flatten significantly or even
drop before reaching the vacuum (at
about 800 hPa or 80 kPa) this indicates
a leakage. In this case change the red
O-rings in the sensor unit.

Changing the O-rings in the sensor unit

Use fine pointed tweezers to pierce the
O-ring and pick it.

Take the spare O-rom from the service
pack. Do not pierce it.

Put O-ring into the hole and let it “snap”
into the groove on the bottom.

If the O-ring does not snap in itself screw
in the tensio shaft cautiously.

72 | Cleaning and maintenance

Note

Do not stick the tweezers tip into the hole of the
sensor unit. You may damage the pressure sensor.

Empty carefully sensor unit and
tensio shafts.

Protect sensor unit from dust.

Store sensor unit and tensio shafts dry.

Storage

If you do not use the HYPROP over a longer period of time make sure to avoid
any algae growth.

73 | Cleaning and maintenance

Additional accessories

Item Picture Description

HYPROP

®

extension set

Ordering no. 020 203

Consisting of sensor unit including tensio shafts
and connection cable

HYPROP

®

BALANCE

Ordering no. 020 204

USB and HYPROP® port,
weighing range 2200 g,
readout 0.01 g,
reproducibility 0.01 g,
linearity 0.01 g

HYPROP

®

Refill Unit
230 V

ordering no. 020 257

110 V

ordering no. 020 258

Complete for one HYPROP

®

consisting
of laboratory vacuum pump (end vacuum
value 8 hPa (0.8 kPa)) below the atmospheric
air pressure, HYPROP

®

Vacuum Mount,

HYPROP

®

Beaker Mount

HYPROP

®

Beaker Mount

Ordering no. 020 262

Stainless steel mount, 2 beakers, 4 filling adapters

HYPROP

®

Vacuum Mount

Ordering no. 020 268

-

HYPROP

®

Vacuum Pump
230 V

ordering no. 020 259

110 V

ordering no. 020 260

End vacuum value 8 hPa (0.8 kPa)
below the atmospheric air pressure,
20 l/min, for lab use only

HYPROP

®

tensio shaft
50 mm

ordering no. 020 277

25 mm

ordering no. 020 281

Including O-rings

HYPROP

®

Sat

Ordering no. 020 253

HYPROP® saturation plate

HYPROP

®

Training

Ordering no. 020 254

Incl. instruction material,
training hours: approx. 4

HYPROP

®

Adapter
for 2” sample rings

Ordering no. 020 271

HYPROP

®

Silicone Gasket

Ordering no. 020 267

74 | Additional accessories

Produkt/Dienstleitung Abbildung

HYPROP

®

refilling
attachment

Ordering no. 020 263

For HYPROP

®

sensor unit, with filling valve

KSAT

®

Automated system
for measuring the
saturated hydraulic
conductivity of soil
samples

Ordering no. 020 1

Incl. KSAT

®

VIEW software, 5 l storage tank,

1.2 m inlet tube, 1.2 m outlet tube, 2 gaskets
for crown, trough for saturating the soil sample,
stainless steel plate for testing the pressure
sensor, USB port, 1 sample ring SZ 250

UMS sample ring
SZ250 for HYPROP

®

,

KASAT

®

or BaPS 250

Ordering no. 100 101

Volume 250 ml, outside Ø 84 mm, inside 80 mm,
height 50 mm, stainless steel, friction reduced
polished surface for minimal soil compression,
laser marked consecutive 6 digit ID number
and tare with 0.1 g accuracy, incl. 2 plastic
protection caps

UMS hammering
adapter SZA250

Ordering no. 100 201

For sample rings 250 ml with outside Ø 84 mm,
stainless steel, length 300 mm, with impact
protection grip

UMS sample rings
SZ100

ordering no. 100 102

SZ100-2"

ordering no. 100 103

Volume 100 ml, outside Ø 60 mm, inside 56 mm,
height 40.5 mm, stainless steel, friction reduced
polished surface for minimal soil compression,
laser marked consecutive 6 digit ID number
and tare with 0.1 g accuracy, incl. 2 plastic
protection caps

Like SZ100, apart from outside Ø 53 mm,
inside 50 mm, height 51 mm

UMS hammering
adapters
SZA 100

ordering no. 100 202

SZA 100-2"

ordering no. 100 203

For sample rings 100 ml with outside Ø 60 mm,
stainless steel, length 300 mm, with impact
protection grip

Like SZA100 apart from outside Ø 53 mm

PE hammer

Ordering no. EJ040
505

Blow-back proof, Ø 70 mm, 2.0 kg

HYPROP

®

tensio shaft set

Ordering no. 020 255

Set with 1 x 25 mm and 1 x 50 mm tensio shaft,
incl. O-rings

75 | Additional accessories

Theory

Preliminary note

HYPROP (HYdraulic PROPerty analyser) is a device to measure hydraulic
key functions of soil samples in a comfortable and reliable way by using an
evaporation experiment.

Wind (1966) developed the evaporation method in the mid-sixties. For this 5
tensiometers were put in a soil sample. The sample was set on a balance and
over the evaporation process the tensions and the mass change of the samp­le were measured in time intervals. Based on these data the water retention
function and the unsaturated hydraulic conductivity in the range between
saturation and maximum 500 hPa (50 kPa) were calculated by means of an
iteration process. Schindler (1980) simplified this method. He used only 2 ten­siometers and simplified the evaluation procedure. HYPROP is working based
on this method. The method was tested several times and its fitness for use was
proven by scientific analysis (Wendroth et al., 1993, Peters and Durner, 2008;
Peters et al., 2015). New research results yielded a further simplified measuring
procedure (Schindler and Mueller, 2006) and an extended measuring range
(Schindler et al., 2010a and Schindler et al., 2010b). Using the HYPROP one can
today measure simultaneously the water retention curve and the unsaturated
hydraulic conductivity function in the range between water saturation and
close to the permanent wilting point. The measuring time amounts – depen­ding on the soil – from 2 days (clay samples) to maximum 10 days (peat and
sand samples). Additionally the dry bulk density of the sample is determined.

The measurement and evaluation can be run in two modes. In the multi ba-
lance mode (one balance per sample) the lab employees’ work effort is limi­ted to set up and take away the samples. In the single balance mode (one
balance for more samples) up to 20 samples can be measured in parallel. In
this mode it is necessary to put the probes manually on the balance twice a
day. This takes about 15 s per sample and weighing. The measurement of the
tension runs automatically. The software HYPROP-VIEW enables a comforta­ble data logging and storage. The software HYPROP-FIT provides the same
comfort for data evaluation, fitting and export of the hydraulic key functions.
The hysteresis of the saturation and dewatering characteristics of the hydrau­lic key functions is described in Schindler et al. (2015).

76 | Theory

Measurements considering the shrinkage characteristics of the soil sample
are described in Schindler et al., 2015. Comparing the measuring results of
HYPROP and classical methods (sand box, kaolin box, pressure pot) demons­trated good congruence (Schelle et al., 2010, 2011, 2013a, b; Schindler et al.,

2012). Systematical differences could not be found.

Measuring method

HYPROP® measures the water tension/water content relation (“retention curve”,
“pF/WC curve”) of a soil sample. It also measures how the unsaturated
hydraulic conductivity depends on the water tension/content (“Ku curve”).
This is based on the evaporation method according to Wind (1968) in Schindler’s
model (1980).

With this method two tensiometers are positioned in two depths of a soil samp­le sitting in a sample ring. The plane in the middle between the two tensiome­ters is identical with the horizontal symmetry plane of the column. The sample
is saturated with water, basally closed and set on a balance. The soil surface
is open to the ambient atmosphere so that the soil water can evaporate.
HYPROP measures the water tension in two horizons of the soil sample over
the evaporation process by means of two vertical tensio shafts (similar to T5
tensiometers) . The change of the sample mass over time is determined by
weighing. The medial pF value of the sample is calculated based on the aver­age value of the two tensions. The medial water content is calculated based
on the mass change. This results in one measuring value per point in time for
the pF/WC curve.

The evaporation rate results from the mass differences, based on this the vo­lume flow is calculated at each point in time. The values of the hydraulic
conductivity with increasing desiccation are a result of how well the soil can
transport this water to the top where it evaporates. If the conductivity is poor
the soil on top dries out whereas it remains wet on the bottom. So the upper
tensio shaft indicates “drier” than the lower tensio shaft which is still “wet”. If
the conductivity is good the whole water of the sample is evaporated and
bother tensio shafts indicate almost the same values. The detailed calculation
basics of the method as well as the check of its validity are explained in Peters
and Durner (2008) and Peters et al. (2015).

77 | Theory

The terms tension, matrix potential, water tension and pF value refer to the
same physical value: they describe the energy that attracts water mole­cules – to pores capillary or to soil particles adhesively. Plants e.g. must
overcome this binding energy (or attraction force), to suck water from the
soil matrix.

The water is under tension in the soil. This tension or attraction force can be
directly measured as a vacuum of the water compared to the atmospheric
pressure. So for the measurement water in the tensio shaft is “offered” to
the soil. The soil sucks it with the same force as it retains the water. As the soil has
a capillary contact to the water in the tensio shaft through the pores of the
ceramic the pressures of the water in the soil and in the tensio shaft finally match.

As the tensio shaft water is locked air tight, it cannot flow into the soil before
the soil is so dry and accordingly the vacuum is so high that the first pore
layer gets empty. This vacuum (tension) can be measured with a pressure
sensor. If the vacuum is strong enough to suck the small pores empty the
water entry point has been reached: air enters the tensio shaft, the pressure
rises up to the atmospheric pressure and the pressure read out drops to zero.

The matrix potential is the negative value of the tension. It is often expressed
in hPa or kPa. In the soil science also the pressure head is used, e.g. in the
unit “cm water column”. The pF value is the decimal logarithm of a wa­ter column in cm. A soil water tension of -100 hPa is equivalent to a water
column of approximately* 100 cm. So its pF value is 2.0

The terms retention function, pF curve and pF/WC characteristics mean the
same. They describe a soil characteristic dependent on the binding energy
(pF value, water tension) and on the water content (WC). As an example:
Sand can retain only little water, clay a lot. At or near saturation sand con­ducts water very well, clay however poorly. Dry sand conducts water very
poorly, compared to this clay is a bit better (water conducting horizons).
Please see the following retention curves for comparison.

Explanation of terms

* as g = 9.81 m/s²

78 | Theory

Typical retention
curve of sand.

Typical retention
curve of loam.

79 | Theory

HYPROP measures the water tensions h1 and h2 (in hPa or kPa) in two mea­suring levels of the sample at certain points of time t being defined in the
HYPROP-VIEW configuration. In the multi balance mode also the total mass
of the sample is weighed (in g) at the same time. In the single balance mode
the sample mass is weighed manually – usually twice a day. The software cal­culates the medial water content of the sample based on the sample mass
minus all tare components (sensor unit, sample ring, dry mass of the soil). The
dry mass of the soil can be determined after the measurement by drying the
sample in an oven at 105 °C.

The measuring data are evaluated with the software HYPROP-FIT according
to Schindler’s method (1980). The precise calculation of the water content
needs the input of the soil’s dry mass. As long as the dry mass has not been
entered HYPROP estimates the water content upfront. HYPROP-FIT calcula­tes based on linearization assumptions discrete points of the retention and
the conductivity curves. For this in a first step the raw data are interpolated
by Hermitian splines. This has the advantage that differing measuring times
of tensions and water contents can be adjusted and the number of time
points that are used for calculating data are fixed a priori. The default set in
HYPROP-FIT is a calculation at 100 time points that are taken from the splines.

At every calculation time point a medial water content θ

i

is calculated by di­viding the mass of the soil water by the volume of the soil body. Each of these
points is assigned to a tension that is calculated from the measured and avera­ged tensions h

1

and h2. Finally this procedure results in 100 points of the retention

curve θ

i(hi

). In order to calculate the conductivity function it is assumed that

the water flow through a horizontal plane that lies exactly in the middle of the
two tensio shafts (and thus in the symmetry plane of the column) between two
time points t

i-1

and ti is qi = 1/2 (∆Vi/∆ti )/A. With ∆Vi being the water reduction (in

cm³) over the mass change, ∆t

i

the time interval between two calculation time
points and A the cross-sectional area (in cm²) of the column. The data points for
the hydraulic conductivity function are calculated by inverting Darcy’s equati­on: K

i

(hi )= -qi /{(∆hi/∆z)-1}. With hi being the time- and space-averaged tension,

∆h

i

the difference of the two tensions at the two measuring levels, and ∆z the

distance of the measuring levels (i. e. the height difference of the tensio shafts).

Generating discrete data points for retention
and conductivity functions

80 | Theory

HYPROP-FIT filters the unreliable K(h) data pairs near saturation depending on
the measuring accuracy of the tensio shafts (Peters and Durner, 2008). After
this parametric functions θ

i(hi

) and Ki(hi) are adjusted to the measuring points
θ(h) and K(h) gained by non-linear optimization. In HYPROP-FIT the user can

select the type of function; all usual models can be found (van Genuchten,
1980; Brooks and Corey, 1964; Kosugi, 1996; Fredlung-Xing, 1994) in uni- and
bi-modal form as well as in a more sophisticated modelling as Peters-Durner­Iden (PDI) variant (Peters, 2013; Iden und Durner, 2014). You can find a com­plete description of the evaluation procedure as well as the models and the
curve fitting in the HYPROP-FIT manual (http://www.umsmuc.de/static/Ma­nual_HYPROP.pdf) and in Peters et al., (2015).

81 | Theory

The θ(h) and K(h) functions are adapted simultaneously to the data points.
This is essential as distinct parameters (i. e  and n ) at van Genuchten/Mua­lem) influence the shape of both functions.

The adaption is accomplished by a non-linear regression under minimization
of the sum of all assessed squares of the distance between data points and
model forecast. However, the assumption the water content is spread out
linear over the column is not always fulfilled in coarse, pored or structured soil.
Therefore, the so called “integral fit” is applied for the adaption of the retenti­on function to avoid a systematic error (Peters and Durner, 2006). For details of
the fitting procedure and data assessment please refer to Peters and Durner
(2007, 2008) and Peters et al., (2015).

Parameter optimization

Additional notes

Three factors limit or extend the measuring range of the tensio shafts:

• the air entry point

• the water vapor pressure (boiling point)

• the boiling delay.

This value is specific for a porous hydrophilic structure and depending on the
contact angle and the pore size. The air entry point of the UMS tensio shafts is
about 8.8 bars so it does not limit the measuring range.

At a temperature of 20°C the vapour pressure of water is 2.3 kPa above vacu­um. This means: If the atmospheric pressure is 100 kPa at 20°C the water will
start to boil or vaporize as soon as the pressure drops below 2.3 kPa (= 97.7 kPa
pressure difference). At this point the measuring range of the tensio shafts ends.

Please note that the atmospheric pressures announced by meteorological
services are always related to sea level. However the true atmospheric pres­sure at an elevation of 500 meters above sea level is for example only 94.2 kPa
(although 100 kPa are announced). In this case the measuring range at 20°C
is limited to -91.9 kPa. Even if the soil gets drier and drier the tension shown by
the readout will remain at this value. But as soon as the bubble point is rea­ched a spontaneous compensation with the atmospheric pressure occurs.
Then air enters the tensio shaft and the readout will rapidly drop to zero.

Influences on the measuring range

The air entry point of the tensio shaft

Water vapor pressure

The ceramic has a pore size of r = 0.3 µm and therefore cannot block ions.
Thus, an influence of osmosis on the measurements is negligible. If the tensio
shaft is dipped into a saturated NaCl solution the readout will show 1 kPa for a
short moment, then it will drop to 0 kPa again.

Osmotic effect

82 | Theory

Addendum

The following typical curves were kindly provided by Prof. Dr. Wolfgang Durner.

• The measurement process is typical of clay with wide pore size distribution

• The water tensions rise almost two days continuously, but at a moderate slo-

pe. This reflects large pore fraction in clay of almost 10%

• From about 50 hPa (pF 1.7), the tensio shafts are far enough away to allow for

the determination of hydraulic conductivities.

• After two days the tensio shafts are now moving with a greater slope, but still a

rather weak curvature continues. The measurement limit is already reached
a day later. This indicates a limited and simultaneously diversified porosity.

• The spreading of tension values is moderate, which indicates a relatively high

hydraulic conductivity in this area.

• The measurement is completed by the (almost too early) failure of the upper

tensio shaft after three days. At the time the sample is removed about 17%
water.

Site: Wolfenbüttel; soil type: slightly sandy loam. Ls3 (S 35%, U 48%, T 17%); measurements in win­ter 2011 at "Geoökologische Labormethoden 2011", TUBraunschweig. Evaporation: 2,75 mm/d,
temperature: 21°C

Typical measuring curves

Sandy loam (Ls3)

Description of the measuring process

83 | Addendum

• The relatively uniform decrease in the water content with increasing pF and

the drop of the relatively flat K data is characteristic of clays having a wide
pore size distribution.

• The addition of the data point on the bubble point of the ceramic tip (po-

wer users only) fits very well with the independent, measured WP4 data
points, and extends the range considerably.

• As a model to describe the data a bimodal function is needed.

Evaluation

84 | Addendum

Clayey silt (Ut3)

Site: Groß-Gleidingen near Braunschweig; soil type: clayey silt (S: 1%, U: 82%, T:17%); measurements: Prak­tikum Bodenphysik at TU Braunschweig, 2010. Evaporation: 14 mm/d using a fan. Temperature: 20°C

•

The measurement process is typical of a very fine grained substrate.

• The water tensions rise spontaneously immediately after the start of mea-

surement, steeply and continuously. This reflects a very small proportion of
coarse pores. pF 2.0 is reached (under the given conditions with fan) after
a few hours. The loss of water to pF 2 is only about 4%.

• The "spikes" at the beginning of the measurements shows the discontinuous

access of air penetrating into the soil.

• From 100 hPa (pF 2.0), the first parallel tensio shafts are far enough away to

allow for the determination of hydraulic conductivities.

• Both tensio shafts rise unabated with the passage of time and failed relatively

soon. The clayey silt has few large middle pore, the finer middle pore region is
in the time of failure still filled with water, the water content is therefore high.

• The spread of the tension values is moderate over the entire measuring

process, which indicates a relatively high unsaturated conductivity.

• The measurement is completed due to the failure of the upper tensio shaft

after less than one day. At this time the sample has lost about 20% water.

Description of the measuring process

85 | Addendum

• The initially flat and then getting steeper drop down in the water water

content with increasing pF is characteristic of very fine grained and clay
substrates.

• The hydraulic conductivity at pF 2 is very high, but the curve then is even

more steep than in the case of clay.

• The description of the data with models is not a problem, however in dry

areas completely unsure. Suitable models are e.g. the van Genuchten
model, or Kosugi model.

Evaluation

86 | Addendum

Slightly loamy Sand (Sl2)

Site: UMS, soil type: slightly loamy sand (S: 1%, U: 82%, T: 17%), measurements at UMS Soillab, Evapo­ration: 5.7 mm/d, temperature: 23°C

•

The measurement process is typical of sand with low fines

• The water tensions rise spontaneously immediately after the start of measu-

rement, until they reach a level that corresponds to the bubble point. In this
case it is about 30 cm (pF 1.5).

• Small "spikes" at the beginning of the measurements indicate that the air is not

uniform but occur in the system in jerks. This will be shown in the evaluation of
the retention curve.

• The tensio shafts run for a long time completely in parallel, and differ only

around a hydrostatic pressure difference of 2.5 hPa .

• Only after the main pores are being drained, the upper tensio shaft value

initially rises exponentially. The tensio shaft failed very quickly, and the air entry
point of the ceramic tip is reached shortly, while the lower tensio shaft is still in
the regular measuring range.

• The difference of the tensions is suitable only after reaching the exponential

rise, that hydraulic conductivities can be calculated.

• The measurement is completed due to the failure of the upper tensio shaft

after a loss of almost 30% water.

Description of the measuring process

87 | Addendum

The additional data in the dry zone were measured by Lisa Heise within their thesis at TU Braun­schweig /UMS Munich using a device made by Decagon (WP4C). They are documented in Heise's
thesis (http://www.soil.tubs.de/mitarbeiter/dipl_detail.php? id=78).

•

The pronounced air entry point and the steep drop down of the retention
curve after reaching the air entry point is characteristic of the sand.

• The hydraulic conductivity can be determined only from pF 2.0, and then

drops down steeply.

• Suitable models for data description are the Fayer-Simmons model, or the

bimodal model to describe the subsequent drop of the retention values
towards dehydration.

Evaluation

88 | Addendum

Pure fine and middle sand (Ss)

Material: packed quartz sand particle size: 0.1 bis 0.3 mm, soil type: sandy sand (S: 100%, U: 0%, T:
0%), site: Bodenphysikalisches Labor, TU Braunschweig, evaporation: 1.4 mm/d, temperature: 22°C

•

The measurement process is typical of sand with narrow particle size distri­bution and without fines

• The tension rise spontaneously immediately after the start of measurement,

until they reach a level that corresponds to the bubble point. In this case it
is about 50 cm (pF 1.7).

• The tensio shafts run for a long time completely in parallel, and differ only

around a hydrostatic pressure difference of 2.5 hPa.

• After draining the main pore portion the tensio shaft value of the upper ten-

sio shaft rises extremely steep. The failure of the tensio shaft is now very quick.

• The lower tensio shaft is at the end of the measurement still completely

unaffected by the extreme dehydration front, the difference of water ten­sions is very high.

• Hydraulic conductivities can be calculated only for a short period of time.

• The measurement is completed due to the failure of the upper tensio shaft

after removal of 35% water

Description of the measuring process

89 | Addendum

• The very sharply defined bubble point and the extremely steep drop in

the retention curve after reaching the air entry point is characteristic of
pure sand with a uniform grain size.

• The hydraulic conductivity can be determined only within a very narrow

tension intervall, and drops down very steeply.

• Suitable models are the data description Brooks Corey model, the van

Genuchten model of free parameter m or the Simmons-Fayer model.

Evaluation

Standard pF curves

Standard pF curves
(courtesy of Dr. Uwe Schindler,
ZALF Muencheberg)

90 | Addendum

Sample treatment for WP4 measurements
after a HYPROP measurement

Push the soil sample – similar to a plunger
– in half inch steps out of the sample ring
and cut off the protruding soil piece. Let it
drop into an aluminum tray.

Prepare four WP4 cups as well as the
related lids.

Fill the first WP4 cup with sample material
– maximum half of the cup. Close the cup
immediately.

Repeat these steps for cup 2, 3 and 4.
Seal the cups carefully with duck tape.

Measure the samples in the WP4 device
according to its manual.

Weigh the wet samples immediately after
measuring in the WP4.

Dry the remaining soil from the tray in a
drying chamber. Take it out and let it cool
down in a desiccator. Weigh it.

Put the WP4 samples into an oven and
let them dry several hours at 105 °C until
equilibrium is achieved. Take it out and let
it cool down in a desiccator. Weigh it.

91 | Addendum

Units for soil water and matrix potentials

pF hPa kPa=J/kg MPa bar psi %rF

1 -10 -1 -0.001 -0.01 -0.15 99.9993

FC field capacity 1.8 -62 -6.2 -0.006 -0.06 -0.89 99.998

2 -100 -10 -0.01 -0.1 -1.45 99.9926

Standard measuring range
of tensiometers

2.9 ca. 850 -85 -0,085 -0.85 -12.3

3 -1,000 -100 -0.1 -1 -14.5 99.9261

4 -10,000 -1,000 -1.0 -10 -145.0 99.2638

Permanent wilting point 4.2 -15,000 -1,500 -1.5 -15 -219.5 98.8977

5 -100,000 -10,000 -10 -100 -1450.4 92.8772

Air dry,
depending on air humidity

6 -1,000,000 -100,000 -100 -1,000 -1450.4 47.7632

Oven-dry 7 -10,000,000 -1,000,000 -1,000 -10,000 -1450.38 0.0618

Note: 0.981 kPa corresponds to 10 cm water column

92 | Addendum

Add the dry mass of the WP4 samples to
the dry mass of the remaining sample and
enter this total mass in HYPROP-FIT in the
register “Evaluation”.

Enter the WP4 value of pF, gross wet mass
(wet soil + cup), gross dry mass (dry soil
+ cup) and tare mass (cup only) in the
register “Evaluation” and the table “Add
WP4 data points”. This can be done by
cut and paste from a spreadsheet.

The gravimetric water contents are
calculated automatically, converted into
volumetric water contents, and added
to the graphics. When fitting the hydraulic
properties these data have the same
weighing factor as the HYPROP data.
Power user may change this factor.

Technical data

Facts and figures

Sensor unit

Material
Dimensions

Fiber glass reinforced Polyamide
Height 60 mm, Ø 80 mm

Tensio shafts

Ceramic
Shaft material
Total length

Al

2O3

sinter, bubble point > 200 kPa; Ø 5 mm
Acrylic glass; Ø 5 mm
Small tensio shaft: 31 mm
Big tensio shaft: 56 mm

Measuring range

Pressure transducer
Temperature

-3.0 … 3000 hPa (-0.3 … 300 kPa), electronic

-30 … 70 °C

Accuracy

Pressure
Temperature

± 2,5 hPa / d = 0,05 hPa (+100 ... -500 hPa)
± 0,2 K (at -10 … 30 °C) / d = 0,01 K

Power supply

Voltage
Current

6 … 10 V DC
6 mA nominal, 15 mA max.

Chemical resistance

pH range pH3 … pH10,

Limited to media that do not affect silicon,
fluorosilicone, EPDM, PMMA or polyetherimide

Protection

Housing with covered plug IP65 splash water proof

Sensor units

Number of sensor units
supported by tensioLINK

20

HYPROP balance

Connection to computer
Weighing range
Readout
Reproducibility
Linearity
Adjustment

USB
2200 g

0.01 g

0.01 g

0.01 g
internally

93 | Facts and figures

Literature cited

• Brooks, R. H. and Corey, A. T.

(1964): Hydraulic properties of
porous media. Hydrology Paper

3. Colorado State University, Fort
Collins, Colorado.

• Fredlund, D. G., & Xing, A. (1994):

Equations for the soil-water cha­racteristic curve. Canadian geo­technical journal, 31(4), 521-532.

• Iden, S.C., and W. Durner (2014):

Comment to “Simple consistent
models for water retention and
hydraulic conductivity in the
complete moisture range” by A.
Peters., Water Resour. Res., 50,
7530–7534.

• Kosugi, K. I. (1996): Lognormal

distribution model for unsatura­ted soil hydraulic properties. Wa­ter Resources Research, 32(9),
2697-2703.

• Peters, A. and Durner, W. (2006):

Improved estimation of soil wa­ter retention characteristics from
hydrostatic column experiments.
Water Resources Research 42 (11).

• Peters, A. and Durner, W. (2008):

Simplified Evaporation Method
for Determining Soil Hydraulic
Properties. Journal of Hydrology
356 (1-2): 147– 162.

• Peters, A. and Durner, W. (2007):

Optimierung eines einfachen
Verdunstungsverfahrens zur Be­stimmung bodenhydraulischer
Eigenschaften. Mitteilungen der
Deutschen Bodenkundlichen
Gesellschaft 110 (1): 125-126.

• Peters, A. (2013): Simple consis-

tent models for water retention
and hydraulic conductivity in the
complete moisture range, Water
Resour..Res., 49, 6765–6780.

• Peters, A., S.C. Iden, and W.

Durner (2015): Revisiting the

simplified evaporation method:
Identification of hydraulic func­tions considering vapor, film and
corner flow. Journal of Hydrolo­gy, in press.

94 | Literature cited

Note

If you want to cite this manual please use the following information: UMS (2015): Manual
HYPROP, Version 2015-01, 96 pp. UMS GmbH, Gmunder Straße 37, Munich, Germany.
URL http://ums-muc.de/static/Manual_HYPROP.pdf

• Schelle, H., Iden, S. C., Peters, A.

and Durner, W. (2010): Analysis of

the agreement of soil hydraulic
properties obtained from mul­tistep-outflow and evaporation
methods. Vadose Zone Journal 9
(4): 1080-1091.

• Schelle, H., Iden, S. C. and

Durner, W. (2011): Combined

transient method for determining
soil hydraulic properties in a wide
pressure head range. Soil Scien­ce Society of America Journal 75
(5): 1-13.

• Schelle, H., Heise, L., Jänicke, K.

and Durner, W. (2013a): Wasser-

retentionseigenschaften von Bö­den über den gesamten Feuchte­bereich - ein Methodenvergleich.

- In: Beiträge zur 15. Lysimeterta­gung am 16. and 17. April 2013,
HBFLA Raumberg-Gumpenstein.

• Schelle, H., Heise, L., Jänicke, K.

and Durner, W. (2013b): Water

retention characteristics of soils
over the whole moisture range:
a comparison of laboratory me­thods. European Journal of Soil
Science 64 (6): 814-821.

• Schindler, U. (1980): Ein Schnell-

verfahren zur Messung der Was­serleitfähigkeit im teilgesättigten
Boden an Stechzylinderproben.
Archiv für Acker- und Pflanzen­bau und Bodenkunde 24 (1): 1-7.

• Schindler, U. and Müller, L.

(2006): Simplifying the evapora­tion method for quantifying soil
hydraulic properties. Journal of
Plant Nutrition and Soil Science
169 (5): 623-629.

• Schindler, U., Durner, W., von

Unold, G. and Müller, L. (2010a):

Evaporation method for mea­suring unsaturated hydraulic
properties of soils: Extending the
measurement range. Soil Scien­ce Society of America Journal 74
(4): 1071-1083.

• Schindler, U., Durner, W.,

von Unold, G., Müller, L. and
Wieland, R. (2010b): The evapo-

ration method: Extending the
measurement range of soil hy-

draulic properties using the air‐

entry pressure of the ceramic
cup. Journal of Plant Nutrition
and Soil Science 173 (4): 563-572.

• Schindler, U., Doerner, J. and

Müller, L. (2015): Simplified me-

thod for quantifying the hydrau­lic properties of shrinking soils.
Journal of Plant Nutrition and Soil
Science 178 (1): 136–145.

• UMS (2015): HYPROP-Fit User

Manual. UMS GmbH, Gmun­der Str. 37, 81379 München,
Germany, 2015. URL http://www.
ums.muc.de/static/Manual_
HYPROP-FIT.pdf.

95 | Literature cited

• Van Genuchten, M. T. (1980): A

closed-form equation for predic­ting the hydraulic conductivity
of unsaturated soils. Soil Science
Society of America Journal 44:
892-898.

• Wind, G.P. (1968): Capillary con-

ductivity data estimated by a
simple method. p.181–191. In
R.E. Rijtema and H. Wassink (ed.)
Water in the Unsaturated Zone:
Proc. UNESCO/IASH Symp., Wa­geningen, the Netherlands.

Notes

96 | Literature cited

Notes

97 | Notes

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