vanEssen TD-Diver DI8 Series User manual

TD-Diver & Baro-Diver® DI8xx Series

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EssenInstruments B.V.
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errors contained herein orfor incidental or consequential damages in connection with thefurnishing,
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claimfordirect, incidental,or consequentialdamagesarising out of,or inconnectionwith,thesale,
manufacture, delivery, or use of anyproduct. Van Essen Instruments and the Van Essen Instruments
logo, andDiver aretrademarks orregisteredtrademarks of Van EssenInstruments B.V.
Vitonisa registered trademark of DuPontDow Elastomers.
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CE COMPLIANCE STATEMENT (EUROPE)
Wehereby declare thatthedevice(s) describedbelow are inconformitywith the directives listed. In
the eventofunauthorized modification of any devices listed below, thisdeclaration becomes invalid.
Type: Datalogger
ProductModel: TD-Diver (DI801, DI802, DI805, DI810),Baro-Diver (DI800)
Relevant EC Directives and Harmonized Standards:
1999/5/EC R&TTE Directive for Radio andTelecommunications Terminal Equipment in accordance to
annexIII towhich this directiveconformto thefollowingstandards:
Low Voltage Directive per EN60950-1 (2006)+A11 (2011) forProduct Safety testing
standardfor"InformationTechnology Equipment"
EMC Directive EN 301 489-1 V1.8.1 / EN 301 489-17 V1.3.2 Electromagnetic emissionand
immunityfor"InformationTechnology Equipment"
2014/30/EU Electromagnetic Compatibility directive, as amended by EN61326-1:2013
Theproduct(s) to whichthisdeclaration relatesisinconformity withtheessential protection
requirements of 2014/30/EU Electromagnetic Compatibility directive. The products are inconformity
withthefollowing standardsand/orother normative documents:
EMC: Harmonized Standards: EN 61326-1:2013 Lab Equipment, EMC
IEC61000-6-3:2007 Emission standard for residential, commercial and light-industrial
environments
IEC61000-4-2:2009 Electrostatic dischargeimmunity test
IEC61000-4-3:2006 Radiated, radio-frequency, electromagnetic field immunity test
IEC61000-4-4:2012 Electrical fast transient/burst immunity test
IEC61000-4-5:2006 Surge immunity test
IEC61000-4-6: 2014 Immunity to conducted disturbances, induced byradio-frequency fields
IEC61000-4-11:2004 Voltage dips, short interruptions and voltage variations immunity tests
I hereby declarethat the equipment named above has beendesigned to comply withthe relevant
sections oftheabove referenced specifications. Theitems comply withall applicable Essential
Requirements of the Directives.

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Contents
1Introduction.........................................................................................................................................1
Aboutthis Manual ......................................................................................................................1
OperatingPrinciple....................................................................................................................1
MeasuringWater Level...............................................................................................................2
Measuring Temperature.............................................................................................................4
DiverModels...............................................................................................................................4
FactoryCalibration Procedure...................................................................................................5
2TechnicalSpecification .......................................................................................................................6
General .......................................................................................................................................6
Environmental............................................................................................................................7
Transportation ...........................................................................................................................7
Temperature...............................................................................................................................7
Pressure......................................................................................................................................8
SampleIntervaland Methods....................................................................................................9
3DiverInstallation and Maintenance..................................................................................................10
Introduction .............................................................................................................................10
Configuring and Readingthe Diver..........................................................................................10
Installation ina MonitoringWell..............................................................................................13
Installation in Surface Water....................................................................................................13
Use of Diversat VaryingElevation ...........................................................................................14
Baro-Diver.................................................................................................................................14
UseinSeawater........................................................................................................................14
Maintenance.............................................................................................................................15
4AppendixI Use of Divers atVaryingElevation................................................................................16
5AppendixII DiverCommunication Protocol...................................................................................17
Introduction .............................................................................................................................17
SerialPort Settings...................................................................................................................17
FrameFormat...........................................................................................................................17
List of Commands ....................................................................................................................18
6AppendixIII Diver Accessories........................................................................................................23
Diver-Office software ...............................................................................................................23
USBReadingUnit.....................................................................................................................23
Stainless Steel Cable................................................................................................................23
Cable Clip..................................................................................................................................24
Smart InterfaceCable ..............................................................................................................24
Communication Cable .............................................................................................................24
Diver-Mate ................................................................................................................................25
Diver-Link .................................................................................................................................25

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1
1Introduction
The TD-Diver is a compact, groundwater monitoring instrument for continuously measuring level and
temperature in groundwater, surface water, and industrial waters. Thedatacollectedcan be usedto
manage water resources, estimate hydraulic conductivity andother aquifer conditions. Examples of
applications are:
•monitor potable water recharge areas for water supply,
•monitor tailingsponds, dewatering activitiesand water supply levelsof mines,
•general site investigations for construction, and
•contaminant plume monitoring on spill sites, remediation sites, chemical storage facilities,
landfillsitesandhazardouswaste storagesites.
The TD-Diver is aneasy-to-use dataloggerfeaturing state-of-the-art electronics and arobust high
precision pressure sensor for long term accuracy. The absolutepressure sensor requires minimal
maintenanceand re-calibration.
TheDiver®isa dataloggerhousedina cylindrical casingwitha suspensioneyeatthetop. The
suspension eye can be unscrewed and is designedto installtheDiver into the monitoring well. The
suspension eye alsoprotects the optical connector. Theelectronics, sensors andbattery are installed
maintenance-free into the casing. The Diver is notdesigned to be opened.
The name ofthe datalogger, the model number, the measurement range and theserial number are
clearly identified on the sideof the Diver. This information is etched using a laser and is consequently
chemically neutral and not erasable.
AboutthisManual
This manualcontains information about Van EssenInstruments TD-Diverwith part numberDI8xx, see
section2.5,and Baro-Diver® with part number DI800, an instrument designedtomeasure
groundwater levels and temperature and atmospheric pressure andtemperature, respectively.
2contains
thetechnical specificationsfor the TD-Diver andBaro-Diveras well as guidelinesfor Diver
maintenance. Chapter 3covers thedeploymentof Divers. ThisincludesprogrammingtheDiverwith
theDiver-Office software. Subsequently,installation of Diversinmonitoring wellsandinsurface water
is discussed. There are three appendices that describe the useof Divers at varying elevation, the Diver
communication protocol and a list of Diver accessories.
OperatingPrinciple
TheDiverisa dataloggerdesigned to measurewater pressureandtemperature. Measurementsare
subsequently stored in the Diver's internalmemory. The Diver consistsofa pressure sensor designed
to measure waterpressure, a temperature sensor, anda battery that powers the electronics that takes
and storesthemeasurements. TheDiverisan autonomous datalogger thatcan beprogrammed by
the user. The Diverhas a completely sealed enclosure. The communication between Divers and
Laptops/field devicesisbased onopticalcommunication.
The Divermeasures theabsolute pressure. Thismeans that thepressure sensor notonly measures the
water pressure, but alsothe air pressure pushing onthe water surface. Ifthe air pressure varies, the
measured water pressure will thus also vary, withoutvarying the water level. The air pressure can be

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2
measuredby a Baro-Diverand subsequentlybeused in theDiver-Officesoftware to converttheDiver
pressure readings intowater level data.
MeasuringWaterLevel
All Divers establish theheight of a water column bymeasuring the water pressure using thebuilt-in
pressure sensor. As long as the Diverisnot submerged inwater itmeasures atmospheric pressure, just
higher thewater column thehigherthemeasured pressure. Theheight ofthewater columnabovethe
Diver's pressure sensor isdetermined based on the measured pressure.
Tomeasurethese variationsin atmosphericpressure a Baro-Diverisinstalled for eachsite being
measured. The barometric compensation for these variations in atmospheric pressure can be done
usingtheDiver-Officesoftware, seewww.vanessen.com fora free download.It is also possibletouse
alternative barometric datasuch as data madeavailable online.
The barometrically adjusted water values can be related to a reference point such as the top ofthe
monitoring well or Mean Sea Level (MSL) or anyother vertical reference datum.
1.3.1 Converting DiverDataintoWaterLevel
This section explains howtocalculate thewater level inrelation to averticalreference datum using
theDiverandBaro-
The figurebelow represents an example ofa monitoring well inwhich aDiverhas been installed. In
this case weare therefore interested in the height of the water level(WL) inrelation to the vertical
reference datum. If thewater level is situated abovethe reference datum ithas apositive valueanda
negative value ifitis situated below thereference datum.
Thetopofcasing (TOC)ismeasured in relationtothe verticalreferencedatum andisdenoted inthe
diagrambelow as TOC. TheDiver is suspendedwitha cablewithalength CL. Ifthecable length is not
exactly known, itcan be calculated from a manualmeasurement as described in section 1.3.2.
TheBaro-Diver measuresthe atmosphericpressure (pbaro) and the Diver measures thepressure
exerted by the water column (WC) abovethe Diver and the atmospheric pressure (pDiver).

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The water column (WC) abovethe Diver can be expressed as:
   
 (1)
wherepisthepressure incmH2O, g istheacceleration due togravity (9.80665m/s2) and ρisthe
densityofthewater (1,000kg/m3).
Thewaterlevel (WL) in relationtotheverticalreference datumcanbecalculated as follows:
     (2)
BysubstitutingWC from equation(1)inequation (2) we obtain:
     
 (3)
1.3.2 Calculating theCableLengthfromaManualMeasurement
If thecable length is not exactly known, it canbe determined using amanualmeasurement, see the
figurebelow. The manual measurement(MM)istaken fromthetopofcasing to thewater level. The
valueofthe water levelispositiveunless, inexceptionalcircumstances, thewater level issituated
above thetop of casing.
Thecablelength cannowbecalculatedas follows:
     (4)
where thewater column (WC)iscalculated based onthe measurements takenby the Diver andthe
Baro-Diver.
Notes:
•Ifthepressuremeasured bythe Diver andtheBaro-Diver is measuredat different points in
time, itis necessary to interpolate. The Diver-Office software automatically performsthis
interpolation.
•It is possibleto enter manual measurements into the Diver-Office software. The software
subsequently automaticallycalculates thecable length.
1.3.3 Example
The top ofcasing is measured to be150 cm above the Mean Seal Level (MSL): TOC = 150 cm. The cable
length is notexactly known and therefore a manual measurement is taken. It turns out to be120cm:
MM =120 cm.

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TheDivermeasures apressureof1,170 cmH2O and the Baro-Diver measuresa pressure of 1,030
cmH2O. Substituting thesevalues intoequation (1), results ina watercolumnof 140cm abovethe
Diver:WC= 140cm.
Substitutingthe values of the manualmeasurement and thewater columninequation (4) results in
thefollowing cablelength:CL =120 +140 =260 cm.
Thewaterlevel in relationto MSL can now beeasily calculated using equation (2): WL= 150 260 +
140 =30 cm aboveMSL.
MeasuringTemperature
AllDivers measure the groundwater temperature.This can,forexample, provideinformation about
groundwater flows.
Thetemperature is measured usinga semiconductor sensor. Thissensor notonly measures the
temperature, but also usesthe value ofthe temperature at the same time tocompensate the pressure
sensor andelectronics for theeffects of temperature to ensurethe best possible performance.
DiverModels
The Diver models described inthis manual are from the DI8xx Series: the TD-Diver and theBaro-Diver.
Both models measure absolutepressure andtemperature. The summarybelow describes the two
models.
TD-Diver
ThisDiverismanufacturedusing a stainlesssteel(316 L) casingwith a
22mmdiameter. The TD-Diver is capable of storinga maximum of
72,000 measurements (date/time, pressureand temperature) in its
working memory and 72,000 measurements in itsbackup memory.
The TD-Diver samples pressure and temperature at fixed length
intervalsandstores thesevalues in fixed lengthor continuousmemory.
The TD-Diver is availableinthefollowingpressureranges: 10 m, 20m,
50m and100 m.
Baro-Diver
The Baro-Diver is manufactured using a stainless steel (316 L) casing
witha 22mm diameter. The Baro-Diveriscapableof storing amaximum
of 72,000 measurements (date/time, pressure andtemperature) in its
working memory and 72,000 measurements in itsbackup memory.
TheBaro-Diver measuresatmosphericpressureand is usedto
compensatefor the variations in atmosphericpressure measured by the
otherDivers. The Baro-Diver can also be usedformeasuringshallow
waterlevelsupto 1 meter.
TheBaro-Diver samples pressure and temperature at fixedlength
intervalsandstores thesevaluesinfixed length orcontinuous memory.

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5
FactoryCalibrationProcedure
Each Diveris individually calibrated andtested at severaltemperature andpressure values toensure
superior performance. The Diver is calibrated for the lifetime of theinstrument, as long as it isused
within itsspecified range. A calibration certificate isavailable upon request.

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6
2TechnicalSpecification
General
The Baro-Diver is used foratmospheric pressure and temperature measurements. There are four TD-
Diver models withdifferent pressure ranges forpressure and temperaturemeasurements. The table
belowliststhe generalspecifications oftheBaro-Diverand TD-Diver.
Diameter
Ø 22mm
Length(incl. suspension
eye)
~110mm
Weight
~104grams
Materials
Casing
Pickledandpassivated 316L stainless steel
Pressure sensor
Alumina(Al2O3)
Suspension eye
nosecone
NylonPA6glass fiberreinforced 30%
ABS
O-rings
Viton®
Communication
Interface
Optically separated
Protocol
Serial RS232, a limited set ofcommands is available as specified inAppendix
II
Memory capacity
144,000 measurements
working
72,000 measurements
backup
72,000 measurements
Memory
Non-volatilememory.A measurementconsists of
date/time/pressure/temperature
continuous and fixed length memory
Batterylife*
Upto 10 years, dependingon use
Theoretical battery
capacity
10.5 millionmeasurements + 1000× fullmemory readouts +
2000× programming
Clockaccuracy
Better than ±1 minute per year at25 C
Better than ±5 minutes per yearwithin the operating temperature range
CE marking
EMCinaccordance withthe 89/336/EECdirective
Basic EN 61000-4-2 standard
Emissions
EN 55022 (1998) +A1 (2000) + A2 (2003), Class B
Immunity
EN 55024 (1998) +A1 (2000) + A2 (2003)
*The Diver is always in stand-by when not making a measurement. The power consumption of the
integrated battery is dependent on thetemperature and usage.

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7
If theDiver is used, storedor transported for extended periods oftime under high temperature, this
but thisis not permanent. This isnormal behavior for batteries.
Excessiveprogramming, high frequency sampling and data reading will reduce thebattery capacity.
**Theaccuracy of the clockis highly dependentontemperature. Theclock is actively compensated
for temperature inallmodels.
Environmental
Ingress protection IP68, 10years continuously submerged in waterat 100 m
Transportation
Suitablefortransportationby vehicles, shipsandairplanes inthesupplied packaging.
Resistancetovibration Inaccordancewith MIL-STD-810.
Mechanical shock test In accordancewith MIL-STD-810, for light-weight equipment
Temperature -20°C to80 °C(affects batterylife)
Temperature
Measurement range
-20°Cto80 °C
Operating Temperature (OT)
TD-Diver: 0 °Cto 50 °C
Baro-Diver: -10°Cto50 °Cambient temperature
Accuracy(max)
±0.2°C
Accuracy(typical)
±0.1°C
Resolution
0.01°C
Response time(90%offinal value)
3 minutes(inwater)

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8
Pressure
Thespecifications for atmosphericand water pressuremeasurementsvary by typeofDiver.The
specifications below apply at operating temperature.
TD-Diver
DI801
DI802
DI805
DI810
Unit
Water columnmeasurement range
10
20
50
100
mH2O
Accuracy (max)
±2.0
±4.0
±10.0
±20.0
cmH2O
Accuracy(typical)
±0.5
±1.0
±2.5
±5.0
cmH2O
Long-term stability
±2
±4
±10
±20
cmH2O
Resolution
0.2
0.4
1
2
cmH2O
Displayresolution
0.058
0.092
0.192
0.358
cmH2O
Overload pressure
15
30
75
150
mH2O
Baro-Diver
DI800
Unit
Water columnmeasurement range
1.5
mH2O
Accuracy (max)
±2.0
cmH2O
Accuracy(typical)
±0.5
cmH2O
Long-term stability
±2
cmH2O
Resolution
0.1
cmH2O
Displayresolution
0.058
cmH2O
Overload pressure
15
mH2O
2.5.1 WaterColumnMeasurementRange
The heightofwater abovethe Diverthatcan bemeasured.
2.5.2 Accuracy(maximum)
Accuracy is theproximity ofmeasurementresults tothetruevalue. Thealgebraicsumofall theerrors
that influence the pressure measurement. These errorsare due to linearity, hysteresisand
repeatability. During theDiver calibrationprocess a Diver is rejectedifthe differencebetweenthe
measured pressure and the appliedpressure is larger than thestated accuracy.
2.5.3 Accuracy(typical)
At least 68%of the measurements during the calibration check are within 0.05% FS of the
measurement range.

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2.5.4 Long-termStability
The stability ofthe measurement over aperiod whena constantpressure is applied at aconstant
temperature.
2.5.5 Resolution
The smallest change in pressure thatproduces a response in the Diver measurement.
2.5.6 DisplayResolution
Thesmallest incrementinpressure thattheDivercanmeasure.
2.5.7 OverloadPressure
The pressure at which the Diver pressure sensor will catastrophically fail.
SampleIntervalandMethods
Theminimum and maximumsample interval plusthevarious samplemethods available for the TD-
DiverandBaro-Diver arelisted below.
Sample interval
0.5 sec to99 hours
Sample method
Fixed interval
2.6.1 FixedLengthMemory
TheDiverwilltake measurementsat a sample intervalset by the user, forexample everyhour. When
the numberofsamples reaches 72,000, i.e. thememoryis full, the Diver will stop measuring.
2.6.2 ContinuousMemory
TheDiverwilltake measurementsatapresetsample intervaldata.When the memory fillsup,new
samples beginoverwritingtheoldestrecords.

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3DiverInstallationandMaintenance
Introduction
Inpractice theDiveris suspended ina monitoring welland theBaro-Diver is installed at the surface for
recording barometric pressure. Atmospheric pressure data must be usedto compensate the pressure
measurements recordedby theDivers for variations inatmosphericpressure. In principle,a single
Baro-Diver is sufficient foran area with aradius of 15 kilometers depending on terrain conditions. Also
seeAppendixI UseofDiversat VaryingElevation. A 10-meter change inelevation is theequivalent of a
barometric pressurechange ofapprox. 1cmH2O or1mbar.
The following sectionsdescribe how to install the Diver andBaro-Diver.
ConfiguringandReadingtheDiver
A Diver mustbe programmed with the desired sample method, sample interval, and monitoring point
namebefore itis deployed. The Divers canbe programmed, started, stopped andits data readusing
the Diver-Office software. Thelatest versionof Diver-Office can bedownloaded for free from
www.vanessen.com. Once the softwareisinstalled, a Diver can be connected to thecomputer through
a USB ReadingUnit (part no AS330), aSmart Interface Cable (part no. AS346)ortheDiver-Gate(M)
(partno.AS345).
3.2.1 ConfiguringaDiver
OpentheDiver-Officesoftware and clickthe Diver buttontoopenthe Diver window.See the image
below foranexample where thefollowing settings areused:
•-
•Fixed Fixed-
•recordinterval: 1 hour.
After entering the settings, the Diver must beprogrammed by clicking the Program button.

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Oncethe settingsaresuccessfully programmed intotheDiver the Start buttonwillbeenabled.
ClickingtheStart button opens the Start Diver dialog as shownbelow. Here youcan select fromthe
following three startmethods:
•Immediate Start - Select this option to start the Diver immediately. Upon clicking [Start], the
Diverwillbegin to take andrecord samples, as definedintheDiversettings
•FutureStart - Selectthisoption to start theDiver at a specifiedtimeinthe future. Usethe
date andtime boxes toenter the desired futurestart time.
•Smart Future Start - Thisoption is useful in situations where you want tostop the Diver,
download its data andthencontinuecollectingdataat the specifiedsampleinterval.
After selecting thedesired start method, click the [Start] buttontosave thestart settings totheDiver.

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3.2.2 ReadingDatafroma Diver
ClicktheData button todownloaddata fromtheDiver.Clickthedown arrow nexttothe Data button
to change the mode/type of datadownload:
Depending on thesample interval thefollowing 3options are available:
•Data - downloadall the data recorded bytheDiver.
•NewData- download onlynewly recorded data (sincethe lastdata download). Thisoptionis
notavailable whenthesample interval is5seconds orless.
•BackupData - downloaddata fromtheprevious monitoringsession.
During thedata download the progress is indicated by aprogress bar.Oncethedatahas been
downloadeditwill be exported if this optionisselected intheProject Settings. Subsequently, the
program will jump tothe tree view where the downloaded time series will beselected and a
graph/table ofthedatawillbe shown.

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13
InstallationinaMonitoringWell
Divers arenormally installed below thewater level/table in
a monitoring well. Thedepth at whicha Diver can be
suspendeddepends
range. Further information about the Div
contained inthe chapter 2Technical Specification.
First determine the length of thenon-stretch suspension
cable (part no MO500) based on thelowest groundwater
level.Provide for the required additionallengthfor
attachingthecable to the suspension eye of theDiver and at
theupper end whenyoucutthe wireto size.
Next use cableclips (part no MO310) to attach the endsof
suspension eye, respectively.
To determine the distance of thepressure sensor in the
monitoring well requires thepreciselength ofthecable to
beknown, to which the distanceto the locationofthe
pressure sensor inthe Diver must beadded to obtain the
overall effective cablelength. Thisis depicted in the
diagram below.
It isalso possible toinstall theDiverwitha communication
cable(partnoAS2xxx).This cableallows you to readoutthe Diver at thetop of the monitoringwell by
usingaUSBinterface cable (partnoAS327).
Note that insmall diameter wells the installation andremoval of theDiver may affect thewater level.
IftheTD-Diver replacesa Mini-Diver(part no DI5xx),Micro-Diver (partno DI6xx) or Cera-Diver(partno
DI7xx),the effective cable length must bedecreased by 19 mm so that theposition of the measuring
point,i.e.thepressure sensor,remainsattheidenticalelevation.
InstallationinSurfaceWater
If a Diver is usedin surfacewater it is important that there is
ssensor.
Sedimentation, algae andplant growth shouldbeminimized
asmuch as possible to ensure the Divermeasures the
surrounding water level.
Position the Divers deep enough so that they remain
below a possible ice layer.
A steel protective cover that canbe locked should be used to
prevent vandalism or theft of theDiver.
In thepicture on the righta steel protectivecover attached to
awoodenpost is shown.Inside the protectivecover is a
monitoring tube/screencontaining a Divertomeasure the
l

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Divers canalso beused toindirectlymeasure discharge. Inthiscase, theDiver is installed in a
monitoring tube/screen next to a weir. The picture below shows a Diver installed next to a V weir to
measuredischarge.
UseofDiversatVaryingElevation
Divers canbe used at anyelevationranging from 300 meters below sealevel to 5,000 meters above
sea level.Appendix Icontains further information onthe useofDivers at varyingelevation.
Baro-Diver
TheBaro-Diver must beinstalled in such away that it only measuresatmospheric pressure under all
conditions. A location that is not subject torapid temperature variations is preferred.
UseinSeawater
Do not use the TD-Diver in seawater.
The TD-Diver is made of 316Lstainless steel.Thismaterial isnotsuited for brackishand/or seawater
because it issubject tocorrosion. Corrosion is causedby the salt content and canbe enhanced by
temperature and theother substances inthe water.
Werecommend the Cera-Diver(partno DI7xx) and/or CTD-Diver (part no DI28x) for use in semi-saline
water/seawater. These Divers have a ceramic casing that does notcorrode.

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Maintenance
3.8.1 Frequency
Itisimportant to perform scheduled maintenanceonequipment andmonitoring wellsto sustainthe
accuracy and longevity of the installation.
Thefrequency of this maintenance depends onthecharacteristicsofthedeploymentsite, such as the
degreeoffouling. Appropriatemaintenance schedules should be developedbased onsiteconditions.
Itisrecommended to checkinstruments oftenduring the firstportionofthe deployment to determine
thefrequency of maintenance. General maintenanceshouldbeperformed as often as possible.
3.8.2 Diver
When installed,theDiver doesnotrequire anymaintenance. The casingcanbecleaned withasoft
cloth. Calcium and other deposits can beremoved with a commercially available acidic cleaner such
as whitevinegar. Theflow-through openingcanalso berinsed withwater and/or a diluted acidic
solution.
Notes:
•Only usediluted acidic solutions if the Diver has severebuild-upof,forexample, limescale
andother cleansers arenoteffective.
•Neveruseany hard brushes, abrasives orsharp objects for cleaningtheDiver and always
rinseitproperly with cleanwateraftercleaning, particularly near the flow-through openings.
Donotuseany powerfuljets. This could damagethe pressuresensor.

©July 2023VanEssenInstruments.Allrightsreserved. www.vanessen.com
16
4AppendixI UseofDiversatVaryingElevation
Divers canbeused atany elevation ranging from 300 meters below sea levelto 5,000 meters above
sea level. It is however recommended that all Divers and the Baro-Diver forming part of the same
network beused at thesame elevation (whenever possible).
Therelationship betweenatmospheric pressurevariationsandelevation is exponential, ratherthan
linear:
PH=P0·exp[ (M·g·H)/(R·T)]
where
PH=atmospheric pressureat elevation height H
P0=atmospheric pressure at reference height
M=28.8·10-3 kg/mol (molecular mass ofair)
g=9.81m/s2(standard gravity)
H =height in meters
R =8.314 J/mol/K (gasconstant)
T =temperature in Kelvin
If theBaro-Diver is placedat a different elevation from the other Divers in a monitoring network, it is
possiblefor a deviationtooccur in the barometricallycompensateddatadue to the relationships
referred to above. Thegraph below illustrates the deviation in thebarometric data asa function of the
variation in elevation at5 C and25C.
Todeterminethe relativebarometric pressuredeviation relative to P0at5C(T = 278.15K) at aheight
differential ofH, theabovereferenced formula canbe used:
(PH-P0)/ P0= 1 exp[ (M·g·H)/(R·T)] × 100% (5)
By substitutingthedata, a relative deviation of1.2 % at aheight differential of100 mis obtained. Ata
height differential of1,000 m thisincreases to11.5 %.
Wethereforerecommendthat all Divers and theBaro-Diversinanetworkbe placedsuch that the
mutual height differentials are minimized.
If necessary, multiple Baro-Divers can bedeployed toavoid theabovementioned issues.
0%
5%
10%
15%
20%
25%
30%
01000 2000 3000
deviation [%]
altitude [m]
5 °C
25 °C