Dynamax HPFM3 User manual

Revision: JUNE 2017 1
High Pressure Flow Meter
Installation and Operations Manual
10808 Fallstone Rd Suite 350
Houston, TX 77099 USA
Toll Free: 1-800-896-7108
Phone: [phone] FAX: [phone]
E-mail: [email protected]
International Email: [email protected]
Website: www.dynamax.com

Revision: JUNE 2017 2
Table of Contents
1. Features and What is New in HPFM3.................................................................................4-6
1.1 HighPressureFlowMeter(HPFM)Form&Function.........................................................7-8
1.2 Personal Computer Requirements ...................................................................................8
1.3 Pressured Bottle Requirements........................................................................................8
1.4 Unpacking.........................................................................................................................9
1.5 What to Keep!...................................................................................................................9
2. Quick Start Guide.........................................................................................................................10
3. Application and Theory of Operation..................................................................................11-13
3.1 Why use the HPFM?........................................................................................................11
3.2 Transient Measurements of Conductance of Roots....................................................11-13
3.3 Quasi-steady State Measurement of Hydraulic Resistance, RQS..................................13
4.0 HPFMInstallationGuide...........................................................................................................14-26
5.0 Setup for the HPFM.................................................................................................................27-38
5.1 Operational Imerperative.................................................................................................27
5.2 Valve Setting for Preparing the HPFM for Service.......................................................27
5.3 Pressurizing the HPFM....................................................................................................27
5.3.1 Tips for Setting the Pressure Regulator.............................................................................................28
5.3.2 Preparing the Compressed Air Supply System for use with HPFM...................................................29
5.4 Adding Degassed Water to the HPFM..............................................................................30
5.4.1 Making Degassed Water/ Preventing Algae Buildup Inside the HPFM.....................................31
5.4.2 Priming a Totally Empty Captive Air Tank (CAT)........................................................................32-33
5.4.3 Adding water to a Partly Empty Captive Air Tank (CAT)............................................................33-34
5.5 EliminationAir from the HPFM......................................................................................34-35
5.5.1 Purging Air from the Water Filter................................................................................................35-36
5.5.2 Removing Air Trapped in the 8-way Manifold..............................................................................36
5.5.3 Removing Microscopic Air Bubbles from the Pressure Transducers........................................37
5.5.4 Removing Microscopic Air Bubbles from the HPFM-Bleeding..................................................37
5.6 Storing the HPFM............................................................................................................38
6.0 Software Operation.................................................................................................................39-55
6.1 System Connections.......................................................................................................39
6.2 HPFM Operation Guide...................................................................................................40
6.3 Set-Zero dP-Transient Conductance Preparation......................................................40-41
6.4 Transient Measurementof Conductance.....................................................................42-45
6.4.1. Measurement of the Transient.....................................................................................................42
6.4.2. Regression of the Transient, Current Data.................................................................................45
6.5 Regression of Transient, Saved Data (.trn) Files........................................................46-47
6.6 Introduction QSS Quasi-Steady State.........................................................................48-52
6.6.1. Getting Started...............................................................................................................................48
6.7 Graphics Operation....................................................................................................53-54

Revision: JUNE 2017 3
Table of Contents
7.0 Raw Data for K, and Temperature Corrections.....................................................................55-57
7.1 TemperatureCorrectionwithBuiltinSensor...............................................................................55
7.2 CorrectionsatTestTemperature.................................................................................................55
7.3 RawDataTables,ProjectData...................................................................................................56
7.4 K25-ConductanceatStandardTemperature..............................................................................56-57
8.0 Obtaining Good Data, and Data Presentation.....................................................................58-61
8.1 Wound Response (Plugging of Stems)..........................................................................58
8.2 Air evenly distributed in the wood of a large branch......................................................58
 8.3 Cautions when measuring small ows/conductance or larger resistances...................58
8.4 Air Bubbles...................................................................................................................59-61
9.0 Connecting the HPFM to the Roots and Shoots................................................................62-67
10. Disconnecting the HPFM ......................................................................................................68
10.1 Valve Settings for moving the HPFM...........................................................................68
10.2 Disconnecting and Moving the HPFM..........................................................................68
11. Maintaining the HPFM.............................................................................................................69
11.1 Changing the Water Filter.............................................................................................69
12. Calibration of the HPFM..........................................................................................................70-77
Appendix I Parts List.....................................................................................................................78
Appendix II Bill of Materials.........................................................................................................79
Appendix III Trouble Shooting and FAQ.....................................................................................80-81
Appendix IV Reference List.........................................................................................................82-83
Appendix V Glossary....................................................................................................................84-87

Revision: JUNE 2017 4
1. Features and What is New in HPFM3
Here is a new and updated HPFM product based on the Dynamax history of 15 years of producing this leading plant characterization
instrument.
• New High Res Generation 3 HPFM
• Reading Sensors direct in parts per million
• NIST calibration standard feature
• Instant data regression, and auto-saver
aged results
• USB powered data acquisition
• New High speed sensor conversion
module
• Flow ranges increased by 50%
• Vista, XP, supported
• Windows 7 compatible
• Upgrade packages available to previous
HPFM systems, with new factory calibration
TheHPFM-Gen3measureshowwatermovementrelatestothepressuredi󰀨erencesrequiredtodrawwaterfromthesoil
or through a plant.
The hydraulic conductivity relationship is a quantitative analysis for roots and stems. The measurement is performed in the
eld,wherein-siturootsystemcanbemeasuredinitsnaturalenvironment.
In most cases, the analysis of a sample root or shoot is completed in as little as 10 minutes. HPFM-Gen3 measures the
major components of the hydraulic conductance in the soil-plant-atmosphere continuum (reference #70.) The hydraulic
architecture of a whole shoot or of a single leaf can be represented by a resistance diagram similar to the electronic circuit
shown.Onecanmeasurethevaluesoftheindividualhydraulicresistances,thencomputethepatternofwaterowand
waterpotentialsintheresistancenetwork.Eachhydraulicresistanceelement(R)equalsthepressuredi󰀨erencedrivingow
throughtheelementdividedbytheresultingow(F)(reference#82).
AlldatasetsaresavedwithintheProjectManagerframeworklestructure.TransientresultsaswellasQSSowmeterdata
are saved for easy viewing in with Excel, including the computed conductance, temperature and averaged results.
Advantages
In the HPFM method, the resistance of the root and shoot are measured separately by pressure perfusion and added
together. The HPFM will help plant physiologists and agronomists look forward to those seasonal studies of root and shoot
progression,waterpotential,orsoiltreatmente󰀨ects.

Revision: JUNE 2017 5
Designed for Two Types of Numerical Analysis
Therstanalysisisanin-situtransientanalysisofhydraulicconductance.HPFMmeasurestheowasthewaterpressure
increaseswhileowingintotherootorshoot.Thesoftwarethenintelligentlycalculatestheslopeoftheincreasedow
andpressure.Thatslopeisthe hydraulicconductance.Thesecondanalysisisaquasi-steadystateowmeter,(QSS),
providingaconstantpressureandowintothesample.Thisderivestheowpressureandconductanceinasteadystate
environment, and computes conductance, as well as hydraulic resistance.
ThecompleteHPFMsystemiseldportablewithdetachablewheelsandbackpack.TheHCFM-XPisacompletely
portable suitcase version of the HPFM-Gen3 (5 range limit).
Software
The HPFM3 comes with menu driven software that is easy to use and straightforward in it’s approach. The software also
includes diagnostics and calibration modes to assure the user of correct readings. All data is saved to the PC hard drive for
later analysis by HPFM or graphing packages.
What’s New
• 1000 times more resolution with a highly advanced analog
processing board (24 bit A/D)
• Highest analog resolution on the market provided
• USB powered Analog to digital circuit – Batteries not required
• Single USB high-speed data stream – No more parallel port to add
• Powerful instant regressions, with chart saving and printing
• All regression and streaming data are saved automatically – No
more hand written data
• Individually calibrated pressure ranges on two pressure sensors
with traceable N.I.S.T. precision
• Accuracy calibrated on all pressure readings ±0.1%,typically r2=.99
• Temperature Monitoring added with automatic Standard Temp
adjustments to 25° C
• Completely revised Windows .NET user application package
• Installation compatibility across all Microsoft OS, Vista, Windows7, XP, NT
• Application Platform Basis on .NET, the workhorse platform for Microsoft Supported developers writing in C#
Specications
Stem Ranges
1 mm to 55 mm diameters
Temperature Sensor
T Thermoscope
Flow Rates
0.7 g/h to 2500 g/h in 6 overlapping ranges
Electronic A/D
24-bit resolution dual Analog / Digital converters
Analog/Digital
One reading every two seconds
Data Interface
USB
Dimensions
13.5” x 12.3” x 20.5” (43 x 31x 52 cm)
Weight
26 lb (12 kg) with back pack and wheels
Capacity
2.1 gal. (8 liter) Degassed Water
Maximum Pressure
90 psi (630 kPa)

Revision: JUNE 2017 6
New Calibrations, Improved Specications
• Sensor zero set provided with linear and 2nd order polynomial regressions removes sensor and board drift between data sets
•Improvedoverlaponconductancerangesby50%Di󰀨erentialpressurecalibratedto180kPa
•SensorNonlinearityremovalbyuniquesoftwareadjustment,1-4thordere󰀨ectsremoved
• Conductance and resistance results at the reading temperature are adjusted according to the calibration temperature
• Temperature adjustments are performed automatically to deliver results at 25° C
•Directowcalibrationincreasedto15pointsfrom12.
•50%increaseintheowrange/pressuredi󰀨erenceforall6owranges
New Graphic Analysis
High-resolutionresultgraphicswithdynamiczoom,detailzoom,autoscale.Steadystateowmeter:resultstranslatedto
• Resistance
• Conductance (new)
• Flow (new)
• Ten Point Average Option
Large, easy to read pressure gauges are digitally painted on screen.
•Colorcodedrangesautomaticallydened
• Audible and graphic warnings provided
to prevent over pressure or out of range
readings
• Flow gauge readout in % of full
scale as well as a detailed 2D chart in
Kg*s-1
• Easy to read raw data display of all
important parameters
• Set-up and control options in one menu
• Protected calibration mode
• All changes to initialization automatically
backed up
Dynamic – Transient Conductance (K) with rapid
conductance regression display.
• Instant regression, with chart view, save and printing
options
• Re-analysis of saved data
• Two types of data exclusion: Min/Max, and Pick points to ignore
New Project Manager organization folders automatically organize your data by date. Data sets are saved to the designated
folder,withcomments.Calibrationles,initializationandset-uplesaresavedseparatelyfromdata.
Interactive Help Options, Documentation built into application are coming soon.

Revision: JUNE 2017 7
1.1 High Pressure Flow Meter (HPFM) Form & Function
The HPFM is shown schematically in Figure 1. It is an apparatus designed to perfuse water into an object while rapidly
changing the delivery pressure and simultaneously measuring flow. This is referred as a transient conductance
measurement. The slope of flow plotted versus pressure equals the hydraulic conductance of the object. The object
can be an excised shoot or excised root system or capillary tube (for test purposes). The HPFM may also measure quasi-steady
stateconductance,i.e.,underconditionswhereowandappliedpressureareapproximatelyconstantwithtime.
To measure a transient, a rapid change in water pressure is achieved using a pressure regulator (R), a needle valve
(NV), and a captive air tank (CAT). A pressure regulator (R) delivers compressed air from the compressed air tank (CAT).
The pressure regulator keeps the compressed air at a steady pressure of 4 to 5 MPa (580-725 PSI) through a needle valve
(NV).
The NV flows are in to the air-chamber (A) of a captive air tank (CAT). A rubber diaphragm separates the air
from water (W) in the CAT. The NV is adjusted to permit a rate of airflow to pressurize the air volume at a rate of
3 to 7 kPa s-1 (approx. 1-PSI s-1). The volumes of air and water are approximately equal in the CAT. The CAT can be
pressurized or depressurized by turning the 3-way ball valve (AV).
A pressure release valve (PR) prevents accidental over-pressurization. The pressure release valve is set to vent air when
the pressure exceeds about 0.6 MPa (87 PSI). Since the pressure in (A) never exceeds 0.6 MPa, and the air supply is
4.2 MPa (609 PSI), the pressure drop across the NV is approximately constant. This allows the rate of pressurization in
the water to be approximately linear with time.
PressurizedwaterowsfromtheCATtothe8-WayInletmanifold(8WI)througha9mmInsideDiameter (ID)nylon-
reinforcedTygontubing.Atadistanceof0.3mfromtheCATthewaterpassesthrougha0.1micronwaterlter,thenthe
diameter of the tubing is reduced to 3 mm Outside Diameter (OD) plastic tube; the plastic tubing is connected to the input
side of the 8WI. The 8WI is shown schematically in Figure 1. The 8WI is an 8-Way HPLC valve of octagonal geometry with
8-tubes emerging from a common point in the center and each tube terminated by a valve.
On the inlet side, the 3 mm OD (1.5 mm ID) tube from the CAT is connected to one of the 8 valves (purple connector on
the HPFM). A pressure transducer (PT1) is connected to another valve (blue connector on the HPFM). On the outlet side
another pressure transducer (PT2) is connected to 8WI (blue connector) as well as the 3 mm OD (1.5mm ID) outlet tube
(purple connector). This leaves 6 pairs of valves available between each 8WI and 8-Way Outlet (8WO) for connection of
narrow-bore capillary tubes (CT).
The capillary tubes are 1.5 mm OD HPLC tubing 0.16 to 1.5 m in length. The HPLC CTs have internal diameters from 0.12
to 0.5 mm. During a measurement, one CT is selected by opening the inlet and outlet valves of the corresponding manifold
(8WI and 8WO). The corresponding CT valves for the unused capillary tubes must be closed. Water ow across the
selectedCTcausesadi󰀨erentialpressure(dP)drop(dP=P1-P2)measuredwithPT1andPT2,respectively.
Figure 1
Schematic of High Pressure Flow Meter (HPFM)
W
A
CT

Revision: JUNE 2017 8
Calibrationcurveswereestablishedrelatingow,F,todPvaluesintherangeof0to180kPa.HPLCcapillarytubesupto
0.25 mm ID have linear calibration curves. HPLC capillary tubes 0.3 mm ID or larger are nonlinear because of the transition
fromlaminartoturbulentow.AllcalibrationsareperformedbyDynamax.
The pressure measurements are made with model PX26-100GV solid-state strain-gauge transducers. The output of the
pressure transducers is logged using a custom-designed, dual channel A/D circuit with 12 bits plus sign accuracy. The
HPFM is supplied with Windows software for controlling the A/D circuits, logging data, and for preliminary data analysis.
TheFlowOutletsideofthe8-Waymanifoldisconnectedbya6-foot(1.8m)lengthofwater-lled1.5mmIDTeonFEP
“Clear”tubingtoacompressiontting(CF).ThisFEPtubingpermitsconnectiontothelargersizeplantorrootbasewith
19-50mmttings(HPCC19-35andHPCC34-50).Additional(1mmID)HPLC“Natural”(lighttan)tubingissuppliedforuse
onsmallersizedrootsandshootswith1-20mmttings(HPCC1-4,HPCC4-10andHPCC10-20).Wealsosupply0.127
mm ID ‘RED’ tubing, which is used to assist air bubble removal in the system AND to use for test measurement. This red
tubehastheconductanceofasmallseedlingwithabout100to200cm2ofleafarea.Arangeofcompressionttings
is supplied to permit connection to stems ranging from 1 to 50 mmOD.
1.2 Personal Computer Requirements
Theprogram that controls the High Pressure Flow Meter isGen3 is installed under a program le directory, to run the
software use an IBM compatible computer with an 800 x 600 pixel screen or better. The computer must be running on 32-bit
Windows XP/2000/Vista, 64-bit WindowsXP/2000/Vista, or Windows 7. Two USB ports are required, one to communicate
with the usb-2404UT analog converters, and one for the USB “Keylock” USB dongle, provided for access to each customer’s
unique HPFM.
The software is installed from a single CD ROM via an Install Shield Wizard in the same manner as most Windows
software. The install shield Wizard will install the program in:
C:\Program les\Dynamax\HPFM.
Therearevedistinctpartstosoftwareinstallation,allowingcustomerstoleveragesoftwarecreatedindependently,by
Microsoft, measurement computing, USB software experts and Dynamax Inc. Installation is covered in detail in Section 4.
1. Install latest Microsoft. NET, if required, the Visual c. frameworks.
 2.InstalltheDynamax,HPFM.exe,andthegraphicsdrivers,calibrationles,initializationles,andexampledata.
3. Install Keylock, the security key to enforce Dynamax copyright protection.
4. Install measurement computing InstaCal, the analog conervsion utility incorporated into our product.
5. Install USB device drivers, that access and control the USB data converters.
See Section 4, “HPFM Installation Guide” for the steps to install the HPFM software:
Dynamax supplys the HPFM with a professional factory calibration traceable to NVLAP calibrate scales and pressure
transducers.ThecalibrationleisincludedonthesoftwarediskunderthelenameHPFM.ini.
1.3 Pressured Bottle Requirements
Dynamax ships the HPFM-C models with a compressed air tank, regulator, and hose for connection to the
HPFM. This tank can be pressured to 2015 pounds per square inch (PSI) or 13,890 Kilo-Pascal’s (kPa). It has
a volume of 24 cubic feet (Cu. Ft.) or 682 liters. The regulator allows control of pressures up to 1,500 PSI or
10,343 kPa. This air tank or bottle cannot be shipped filled, so you will need to fill the bottle (air tank) with a dry
compressed gas. Economically, two gases are best: Nitrogen or dried compressed air. The compressed air tank
can be filled by University physical plants (they can assist you) or distributors such as Air Liquide, Linde, or BOC Gases.
Thesetupforrunningatransitorytestrequiresenoughpressure(600PSIor4,100kPa)todeliveraconstantowofgas
to the HPFM. The pressure regulator requires about 700 PSI in the tank to deliver 600 PSI to the HPFM. It must deliver
thegaswithout“choking”andcausingareducingowofgasoverthetimeperiodofthetest.

Revision: JUNE 2017 9
WARNING!
The compressed air tank must have at least 700 PSI (4,800 kPa) to run a transient pressure
test.
1.4 Unpacking
The HPFM is supplied as a complete unit. No assembly is required. However, there are several accessories that are
packaged with the system such as:
• O-rings
• Compression caps
• Connection and bleeding hoses
• Compression Couplings
• Communications Cable
• Software
Itisrecommendedthatyoutakeafewminutestochecko󰀨andconrmallofthesecomponentswerereceived.Adetailed
Parts and Packing List is included in Appendix I.
1.5 What to Keep!
NOTE:
When unpacking, do not discard the box and packing material.
Dynamax ships the HPFM in a box with material on all six sides. This makes the shipping box the perfect box for you
to ship your HPFM internationally, across the U.S., or back to Dynamax for an annual calibration. Also keep the Lists
of Parts, the software, and the tools that came with the HPFM. The list will come in handy when reordering parts for the
HPFM. The software should be kept as a backup in case of PC failure such as hard drive corruption. The tools, which can
be found in the lid of the HPFM, should be kept there since they will be needed to use the HPFM on a daily basis.

Revision: JUNE 2017 10
2. Quick Start Guide
This section is designed to provide a recipe style reference guide to present the basic steps you should follow to assist the
new user to begin using the HPFM. The manual then provides more detailed instruction on how to complete each step.
1. Fill the Air Supply Tank with Compressed Air or Nitrogen – Section 5.0
2. Prepare 7.6L (2 gallons) of degassed, de-ionized water – Section 5.4.1
3. Prime the Captive Air Tank of the HPFM with degassed deionized water – Section 5.4
4. Eliminate all air from the HPFM by purging air from the CAT and Tygon supply tubing, through the purge valve and
waterlterpurgecaps.ThenbleedthesystemwiththesmallRedcapillarytubeovernighttoremoveanymicroscopic
air bubbles that may have remained in the CAT or the 8-Way valve manifolds. – Section 5.5
5. Insert the security lock provided with each HPFM. Connect the HPFM to a PC via the computer’s USB Port and the
communication port on the HPFM with the communications cable. – Section 6.0
6. Check the LED on the HPFM and launch the program by clicking on the HPFM3 icon. Listen for a beep, and notice the
greenLEDblinkingontheUSB-2404UIAnalogModule.Openaprojectlefoldertocollectdata,orreopenanold
projectle–Section 6.2
7. Set the Zero Flow Volts to zero the transducers before taking measurements. This must be performed each day
before beginning measurements to ensure accuracy – Section 6.3
8. Select the plant that you will be working with and measure the stem size – Section 9.0
9. Cut the sample plants stem and install the Pressure couplings – Section 9.0 Use (1 mm ID) HPLC “Natural” (light tan)
tubingwithttings1-20mm(HPCC1-4,HPCC4-10andHPCC10-20)and(1.5mmID)TeonHPLC“Clear”
tubingwithttings19-50mm(HPCC19-35andHPCC34-50)
10.Determinethecorrectowrangetouseforyourselectedsample.Ifyoudonothavethecorrectowrangeset,your 
measurements will be over-scale and you may think the system is not functioning properly. – Section 6.4
11. For roots begin your experiment with a Transient Measurement function, as this is the quickest method for gathering
hydraulicconductancedataandwillminimizeanyplugginge󰀨ectscausedbytheplantsnaturalhealingprocess.
For large stems you may need other methods – Section 6.5
12.AftercollectingtransientowdatayoucanimmediatelyperformaRegressionanalysisofthedatausingtheHPFM 
software to determine the Hydraulic Conductance of the sample plant. The temperature of the test is automatically
recorded and a correction will convert raw reading to the test temperature KC, and K25- converted to standard
temperature – Section 6.5.2
13. As your understanding of the system develops, begin using the Quasi-Steady State Flow Meter function. By
measuring total resistance of the sample you can determine the contribution that individual components make to the
overall hydraulic conductance of the plant. – Section 6.6
14. Before beginning an intensive experiment be sure to understand all the necessary tips and cautions required to
measure hydraulic conductance successfully – Section 8.0

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3. Application and Theory of Operation
3.1 Why use the HPFM?
The High Pressure Flow Meter has several uses in the analysis of root/shoot studies. Some examples of the uses of the
HPFM are:
• Root conductance in the lab or eld
• Conductance of shoots and petioles with or without leaves
• Root Stress Analysis on trees or crops
• Modeling root to shoot communications
• Transpiration models
• Root water status studies
• Absolute varietal comparison statistics
• Mycorrhizae nutrient/water enhancement studies
• Soil to root conductance statistics
• Crop conductance studies
3.2 Transient Measurements Conductance of Roots
Experiencehasshownthatduringowmeasurementsonroots,owfrequentlydeclinesevenwhentheappliedpressure,
P2, is constant. Reasons for this include:
1. During perfusion, solutes accumulate in the stele by reverse osmosis causing a continual decrease in driving force on
water movement.
2.Naturalwoundresponsesinducedwhentheshootisexcisedcausepluggingofthexylemwithintherstfewcentimeters
of the wound causing a continual decline in K.
Readers are referred to (Tyree et al. 1993 and Tyree et al. 1995) for details. Consequently, the HPFM has been designed
tomeasureKquicklybeforetheabovee󰀨ectsbecomeseriousenoughtoinuenceK.Doingrapidmeasurementraises
other sources of error that need to be addressed.
Therateofwaterowintoroots,F,willexceedtherateofpassagethroughtheroots,Fh,iftherootisinitiallydehydrated
since some of the water will remain behind to re-hydrate cells. But F will exceed Fh even in fully hydrated roots
because pressurization will cause elastic swelling of the roots or the HPFM. F will also exceed Fh because of
compression of any air-bubbles that might be present in the wood, the stem interface, or the HPFM. So F will be given
by:
NOTE:
It is essential that users of the HPFM are aware of potential sources of error and know of
ways to minimize such errors
F = Fh + Fe + Fb (5)
Where:FeistheowassociatedwithelasticswellingandFbistheowtocompressairbubbles(whenpresent).
Iftheowthroughtheobjectmeasuredisalinearfunctionofappliedpressuredi󰀨erencebetweentheoutletofthe
HPFM and atmospheric pressure, we can express Fh as:
Fh = K P2 (6)
Where: P2 is the outlet pressure relative to atmospheric pressure. The volume of the tubing, connectors, and object
measured will increase with P2. If the volume increase is elastic and linear with pressure, then the volume of the
system, V, will be given by:

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V = Vo + P2/e (7)
Where: Vo is the initial volume of the system at P2 = 0 and e is the bulk modulus of elasticity. The time derivative of
Equation(7)givestheowtocausetheelasticvolumechange:
Fe = dV/dt = (1/e) dP2/dt (8)
If air bubbles are present anywhere in the system, they will be compressed according to the ideal gas law as the
pressureoftheuidaroundthebubbleincreases.IfVbisthevolumeofabubbleatabsolutegaspressurePbthen
the ideal gas law gives:
PbVb = nRT = PiVi (9)
Where: n is the number of moles of gas in the bubble, R is the gas constant, T is the Kelvin temperature, and Pi is the
initial gas pressure and Vi is the initial volume. If we write Equation (9) as Vb = ViPi/Pb and take the derivative with
time we get the rate of volume change of the bubble:
dVb/dt = -(ViPi/Pb2)dPb/dt (10)
ThenegativesignofthederivativeindicatesthatVbdecreaseswithincreasingPb.Theowofwatertocompressthe
gas volume is the negative of Equation (10) so we have:
Fb = -dVb/dt = (ViPi/Pb2)dPb/dt (11)
Inthecasewherealloftheairbubblesareneartheoutletsideoftheowmeter,wecanequatePbtoP2+Pi.Piis
the initial absolute pressure of the bubble when P2 = 0. Pi approximately equals 0.1 MPa. The barometric pressure
will determine the Pi. There will also be a small contribution by the surface tension of the air-water interface to bubble
compression.Inthespecialcasewheretheairbubblesareneartheoutletoftheowmeter,thedynamicowwillbe
given by substituting Equations (6, 8 and 11) into (5):
F = K P2 + (1/e) dP2/dt + ViPi/(P2 + 0.1)2 dP2/dt (12)
During normal operation of the HPFM, the inlet pressure P1 increases linearly with time, and after a short time delay
this causes P2 to increase linearly with time to make dP2/dt equal to a constant. This permits easier interpretation of
resultsbecauseitmakestheelasticcontributionaconstanto󰀨settoFh.ThecontributionofthethreetermsinEquation
(12) is illustrated in Figure 2 for the case where P2 increases linearly with time from time = 0 (Figure 2 (A)).
Thecomponentows(Fh,Fe,andFb)andtotalowsareshowninFigure2(B).
A
B
C
D
P2
F F
Fh
FeFbFb
Fe
Fh
P1
P2
Figure 2
Transient Measurements Conductance of Roots
Flow → Pressure → Flow → Pressure →
Time → Time →
PT2 → PT2 →

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It is not possible, in practice, to make P2 increase linearly with time from time 0. This is because an extra conductance
equal to the conductance of the capillary tubes of the HPFM (KCT) is interposed between the pressure transducers that
measure P1 and P2 (see Figure 1). When the full set of equations is derived (not shown) a short time lag is predicted
beforeP2increaseslinearlywithtime(seeFigure2(C)).TheresultingcomponentandtotalowsareshowninFigure
2 (D).
Airbubblesgenerallycanbeavoidedwithintheowmetertubingandapparatus,butsometimesairisinthevessels
and/or intercellular air spaces in the base of roots. Although the compression of air causes an increase in F at any given
P2 during a transient measurement, bubbles cause an underestimation of the root conductance, Kr. This is because
Fb decreases with increasing P2 causing a negative contribution to the slope used to calculate Kr. Fortunately, the
contributionofbubblecompressiontototalowdiminisheswithincreasingpressure.TheslopeoftheFversusP2for
P2 > 0.25 MPa is a reasonable approximation of the hydraulic conductance of the root system being measured. It is
probablygoodpracticetomeasuretransientowsforP2upto0.5MPainordertoreducetheunderestimationofKr
caused by compression of air bubbles.
3.3 Quasi-steady State Measurements of Hydraulic Resistance, QSS
Duringsteady-statemeasurementsofQSS,waterowandappliedpressurearebothconstantandbydenitionthe
waterowintotheobjectmeasuredequalstheowoutoftheobject.Inpracticeitisneverpossibletokeepowand
pressure perfectly constant, so it is best to refer to such measurements as quasi-steady state.
The capillary tubes (CT) on the HPFM have been calibrated, i.e., their conductance, KCT, or resistance RCT = 1/KCT,
hasbeenmeasured.Duringowmeasurements,thecontrolprogrammonitorsthedi󰀨erenceinpressuredPacross
theCT.TheprogramusesdPtocalculatetheow,F,from:
F = KCT dP (1A)
or F = dP/RCT (1B)
Sincetheowintotheobjectcloselyequalstheowout,theunknownhydraulicresistance,RU,canbecalculated
from:
RU = (P2 - PO) /F (2A)
or KU = F/(P2-PO) (2B)
Where: P2 is the pressure recorded by the pressure transducer at the outlet, PT2, and PO is the pressure of the water
where it emerges from the object. In many cases PO is known to be zero. When PO is unknown then RU or KU cannot
be computed. Examples will be given later of instances where PO is unknown. For the rest of this section we will
assume PO = 0 and can be omitted from the equations.
Another useful way of viewing Quasi-steady state measurements is through the Ohm’s law analogue for ow through
resistance in series. For any given resistance, R, in series Ohm’s law states that:
RF = dP (3)
So for the capillary tube in series with the unknown resistance we have:
RCT F = dP (4A)
and RU F = P2 (4B)
So dividing Equation (4B) by (4A) we have:
RU/RCT = P2/dP (4C)
or RU = RCT P2/dP (4D)
or KU = KCT dP/P2 (4E)

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4. HPFM Installation Guide
Please use the following steps to install the HPFM Software onto your PC.
1. Login as an administrator level user.
WARNING!
The HPFM software will NOT OPERATE PROPERLY unless your signed in as the
Administrator user. Turn off Virus Protection and all other applications.
2. Insert the HPFM3 CD in your CD drive. Use Windows Explorer to browse to the root of the CD. For Windows Vista and
Windows 7 users.
3. Right click Setup.exe and select Run as administrator.
4. Navigate to Start Menu - Control Panel – Add/Remove Programs and check if Microsoft.NET framework 3.5 or newer
version is available on your PC.
NOTE:
For Windows Vista and 7 users, Microsoft.NET framework 3.5 is not required and the default
version on your computer is version 4.0.

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5. If upgrade is needed, double-click on dotnetfx35.exe in your CD directory and follow the instructions on the
installation dial
6. After .NET Framework 3.5 installation is completed, double-click on setup.exe to install HPFM software.

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7. Choose directory where you want the software to be installed at (use default directory C:\Program Files\Dynamax\
HPFM\).
8. After the HPFM installation, setup.exe will automatically install Security Key driver. This USB device is used in
conjunction with HPFM for security purpose. Click OK to exit this screen when completed.
9. Next, the process installs the Measurement Computing (MC) - hardware communication and analog data acquisition
software (InstaCal).
10. A new self-Extractor screen will pop up to ask your permission to continue the installation. Click OK to proceed.

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11. The installation of InstaCal program will start, which is essential to HPFM operation. Click on Setup to continue.
12. Click on Next and choose installation directory (use default location).
13. Windows will prompt you to restart your computer after installing all of the above products. Click on Yes to restart.

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14. A successful installation should have the following:
• HPFM and InstaCal icons on your desktop
•HPFMdirectorylocatedatC:\ProgramFiles\Dynamax\HPFM\HPFM.iniisasettingle,whichmatchesthe
calibration data supplied for your serial number and calibration document.
• MC is directory located at C:\Program Files\Measurement Computing\DAQ\

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Note
The cb.cfg le is unique for the HPFM application. The .CFG le denes the A/D
channels and congures them for the pressure readings.
15. For 32-bit Windows XP/2000/Vista:
inorderforHPFMtoreadpressure,check,andthencopyifneededtheCB.CFGlefrom:
C:\Program Files\Dynamax\HPFM\IcalUL\ CB.CFG
has been copied to:
C:\Program Files\Measurement Computing\DAQ\.
For 64-bit Windows XP/2000/Vista:
copytheCB.CFGleto
C:\Program Files(X86)\Measurement Computing\DAQ\.
For Windows 7:
copy CB.CFG to
C:\ProgramData\Measurement Computing\DAQ\.

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16. After installing the CFG files, we will add two drivers
for USB communication. Plug the HPFM USB cable
into one of the USB port on your PC, and connect
to the Measurement Computing USB2404-UI
device under the top of HPFM.
When prompted for New Hardware Found, select Yes,
this time only and click Next. Please select Install the
software automatically.
Another screen will pop up to notify you that a new device
has been detected, click OK to add. The USB carrier is
the generic loader for the USB2404 device.
Click Finish when done.