Vega VEGABAR 81 User manual

Operating Instructions
Pressure transmitter with metallic
measuring cell
VEGABAR 81
Secondary Device for electronic di󰀨erential
pressure
With SIL qualication
Document ID: 48045

2
Contents
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
Contents
1 About this document ............................................................................................................... 4
1.1 Function ........................................................................................................................... 4
1.2 Target group..................................................................................................................... 4
1.3 Symbols used................................................................................................................... 4
2 For your safety ......................................................................................................................... 5
2.1 Authorised personnel ....................................................................................................... 5
2.2 Appropriate use................................................................................................................ 5
2.3 Warning about incorrect use............................................................................................. 5
2.4 General safety instructions............................................................................................... 5
2.5 Conformity........................................................................................................................ 5
2.6 SIL qualication according to IEC 61508.......................................................................... 6
2.7 NAMUR recommendations .............................................................................................. 6
2.8 Installation and operation in the USA and Canada ........................................................... 6
2.9 Environmental instructions ............................................................................................... 6
3 Product description ................................................................................................................. 7
3.1 Conguration.................................................................................................................... 7
3.2 Principle of operation........................................................................................................ 7
3.3 Supplementary cleaning procedures.............................................................................. 10
3.4 Packaging, transport and storage................................................................................... 10
3.5 Accessories.................................................................................................................... 11
4 Mounting................................................................................................................................. 12
4.1 General instructions ....................................................................................................... 12
4.2 Instructions for oxygen applications ............................................................................... 14
4.3 Ventilation and pressure compensation.......................................................................... 14
4.4 Combination Primary - Secondary ................................................................................. 16
4.5 Level measurement........................................................................................................ 17
4.6 Dierential pressure measurement ................................................................................ 18
4.7 Interface measurement .................................................................................................. 19
4.8 Density measurement .................................................................................................... 20
4.9 Density-compensated level measurement ..................................................................... 21
4.10 External housing ............................................................................................................ 23
5 Connecting to power supply................................................................................................. 24
5.1 Preparing the connection ............................................................................................... 24
5.2 Connecting..................................................................................................................... 25
5.3 Single chamber housing................................................................................................. 26
5.4 External housing with version IP68 (25 bar) ................................................................... 27
5.5 Connection example ...................................................................................................... 29
6 Functional safety (SIL) .......................................................................................................... 30
6.1 Objective........................................................................................................................ 30
6.2 SIL qualication.............................................................................................................. 30
6.3 Application area ............................................................................................................. 30
6.4 Safety concept of the parameterization .......................................................................... 31
7 Set up with the display and adjustment module ................................................................ 33
7.1 Parameter adjustment .................................................................................................... 33
7.2 Menu overview ............................................................................................................... 46
8 Diagnosis, asset management and service ........................................................................ 49
8.1 Maintenance .................................................................................................................. 49

3
Contents
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
8.2 Rectify faults................................................................................................................... 49
8.3 Exchanging the electronics module................................................................................ 50
8.4 Exchange process module on version IP68 (25 bar) ...................................................... 50
8.5 How to proceed if a repair is necessary.......................................................................... 51
9 Dismount................................................................................................................................. 52
9.1 Dismounting steps.......................................................................................................... 52
9.2 Disposal ......................................................................................................................... 52
10 Supplement ............................................................................................................................ 53
10.1 Technical data ................................................................................................................ 53
10.2 Dimensions .................................................................................................................... 61
10.3 Industrial property rights................................................................................................. 69
10.4 Trademark ...................................................................................................................... 69
Safety instructions for Ex areas:
Take note of the Ex specic safety instructions for Ex applications.
These instructions are attached as documents to each instrument
with Ex approval and are part of the operating instructions.
Editing status: 2023-09-01

4
1 About this document
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
1 About this document
1.1 Function
This instruction provides all the information you need for mounting,
connection and setup as well as important instructions for mainte-
nance, fault rectication, safety and the exchange of parts. Please
read this information before putting the instrument into operation and
keep this manual accessible in the immediate vicinity of the device.
1.2 Target group
This operating instructions manual is directed to trained personnel.
The contents of this manual must be made available to the qualied
personnel and implemented.
1.3 Symbols used
Document ID
This symbol on the front page of this instruction refers to the Docu-
ment ID. By entering the Document ID on www.vega.com you will
reach the document download.
Information, note, tip: This symbol indicates helpful additional infor-
mation and tips for successful work.
Note: This symbol indicates notes to prevent failures, malfunctions,
damage to devices or plants.
Caution: Non-observance of the information marked with this symbol
may result in personal injury.
Warning: Non-observance of the information marked with this symbol
may result in serious or fatal personal injury.
Danger: Non-observance of the information marked with this symbol
results in serious or fatal personal injury.
Ex applications
This symbol indicates special instructions for Ex applications.
• List
The dot set in front indicates a list with no implied sequence.
1 Sequence of actions
Numbers set in front indicate successive steps in a procedure.
Disposal
This symbol indicates special instructions for disposal.

5
2 For your safety
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
2 For your safety
2.1 Authorised personnel
All operations described in this documentation must be carried out
only by trained and authorized personnel.
During work on and with the device, the required personal protective
equipment must always be worn.
2.2 Appropriate use
As Secondary Device, the VEGABAR 81 is part of an electronic dif-
ferential pressure meaasurement.
You can nd detailed information about the area of application in
chapter " Product description".
Operational reliability is ensured only if the instrument is properly
used according to the specications in the operating instructions
manual as well as possible supplementary instructions.
2.3 Warning about incorrect use
Inappropriate or incorrect use of this product can give rise to applica-
tion-specic hazards, e.g. vessel overll through incorrect mounting
or adjustment. Damage to property and persons or environmental
contamination can result. Also, the protective characteristics of the
instrument can be impaired.
2.4 General safety instructions
This is a state-of-the-art instrument complying with all prevailing
regulations and directives. The instrument must only be operated in
a technically awless and reliable condition. The operating company
is responsible for the trouble-free operation of the instrument. When
measuring aggressive or corrosive media that can cause a danger-
ous situation if the instrument malfunctions, the operating company
has to implement suitable measures to make sure the instrument is
functioning properly.
The safety instructions in this operating instructions manual, the
national installation standards as well as the valid safety regulations
and accident prevention rules must be observed.
For safety and warranty reasons, any invasive work on the device
beyond that described in the operating instructions manual may be
carried out only by personnel authorised by us. Arbitrary conversions
or modications are explicitly forbidden. For safety reasons, only the
accessory specied by us must be used.
To avoid any danger, the safety approval markings and safety tips on
the device must also be observed.
2.5 Conformity
The device complies with the legal requirements of the applicable
country-specic directives or technical regulations. We conrm con-
formity with the corresponding labelling.

6
2 For your safety
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
The corresponding conformity declarations can be found on our
homepage.
Due to the design of its process ttings, the device does not subject
of EU pressure device directive if it is operated at process pressures
≤ 200 bar. 1)
2.6 SILqualicationaccordingtoIEC61508
The Safety Integrity Level (SIL) of an electronic system is used to as-
sess the reliability of integrated safety functions.
For detailed specication of the safety requirements, multiple SIL
levels are specied according to safety standard IEC 61508. You can
nd detailed information in chapter " Functional safety (SIL)" of the
operating instructions.
The instrument meets the specications of IEC 61508: 2010 (Edi-
tion 2). It is qualied for single-channel operation up to SIL2. The
instrument can be used homogeneously redundant up to SIL3 in
multi-channel architecture with HFT 1.
2.7 NAMUR recommendations
As a Secondary Device, the device is part of an electronic dieren-
tial pressure measurement. It fulls the requirements of the NAMUR
recommendations of the respective Primary Devices.
2.8 Installation and operation in the USA and
Canada
This information is only valid for USA and Canada. Hence the follow-
ing text is only available in the English language.
Installations in the US shall comply with the relevant requirements of
the National Electrical Code (NEC - NFPA 70) (USA).
Installations in Canada shall comply with the relevant requirements of
the Canadian Electrical Code (CEC Part) (Canada).
2.9 Environmental instructions
Protection of the environment is one of our most important duties.
That is why we have introduced an environment management system
with the goal of continuously improving company environmental pro-
tection. The environment management system is certied according
to DIN EN ISO 14001.
Please help us full this obligation by observing the environmental
instructions in this manual:
• Chapter " Packaging, transport and storage"
• Chapter " Disposal"
1) Exception: Versions with measuring ranges from 250 bar. These are subject
of the EU Pressure Device Directive.

7
3 Product description
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
3 Product description
3.1 Conguration
The scope of delivery encompasses:
• Pressure transmitter VEGABAR 81 - Secondary Device
• Ready-made connection cable, unassembled cable gland
The further scope of delivery encompasses:
• Documentation
– Quick setup guide VEGABAR 81
– Safety Manual (SIL)
– Documentation instrument parameters (default values)
– Documentation order-relating instrument parameters (deviation
from default values)
– Test certicate for pressure transmitters
– Instructions for optional instrument features
– Ex-specic " Safety instructions" (with Ex versions)
– If necessary, further certicates
Information:
Optional instrument features are also described in this operating
instructions manual. The respective scope of delivery results from the
order specication.
The type label contains the most important data for identication and
use of the instrument:
• Instrument type
• Information about approvals
• Conguration information
• Technical data
• Serial number of the instrument
• QR code for device identication
• Numerical code for Bluetooth access (optional)
• Manufacturer information
To nd order data, documents or software related to your device, you
have the following options:
• Move to " www.vega.com" and enter in the search eld the serial
number of your instrument.
• Scan the QR code on the type label.
• Open the VEGA Tools app and enter the serial number under "
Documentation".
3.2 Principle of operation
VEGABAR 81 is suitable for applications in virtually all industries. It is
used for the measurement of the following pressure types.
• Gauge pressure
• Absolute pressure
• Vacuum
Scope of delivery
Type label
Documents and software
Application area

8
3 Product description
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
Measured products are gases, vapours and liquids.
The chemical seal systems of VEGABAR 81, which are optimally
adapted to the process, also allow measurement of highly corrosive
and hot products.
The electronic dierential pressure measurement is suitable for the
measurement of the following process variables:
• Level
• Flow
• Dierential pressure
• Density
• Interface
• Level, density-compensated
The VEGABAR 81 Secondary Device is combined with a suitable
sensor from the same device series to an electronic dierential pres-
sure measurement. The dierential pressure measurement consists
then of the Primary Device and Secondary Device.
Information:
The sensor versions " Relative pressure climate-compensated" as
well as " Double chamber housing" are not suitable for connection of
a Secondary Device.
1
2
Fig. 1: Example, electronic dierential pressure for level measurement in pres-
surized vessel
1 VEGABAR 81
2 VEGABAR 81, Secondary Device
Measured products
Measured variables
Electronicdierential
pressure

9
3 Product description
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
The sensors are connected via a shielded four-wire cable.The meas-
ured value from the Secondary Device is read in and factored into the
calculations. Power supply and parameter adjustment are carried out
through the Primary Device.
You can nd further information in chapter " Combination Primary -
Secondary " of this operating instructions.
To reach the Safety Integrity Level (SIL) for the electronic dierential
pressure, both instruments must be SIL-qualied.
The process pressure acts on the sensor element via the isolat-
ing diaphragm. The process pressure causes a resistance change
which is converted into a corresponding output signal and output as
measured value.
Measuring ranges up to 40 bar: piezoresistive sensor element with
a transmission liquid, measuring ranges from 100 bar: a dry strain
gauge (DMS) sensor element.
4
1
3
2
Fig. 2: Conguration of the measuring system with piezoresistive sensor ele-
ment
1 Diaphragm
2 Isolating liquid
3 Base element
4 Sensor element
3
2
1
Fig. 3: Conguration of the measuring system with strain gauge (DMS) sensor
element
1 Pressure cylinder
2 Process diaphragm
3 Sensor element
Relative pressure: the measuring cell is open to the atmosphere.
The ambient pressure is detected in the measuring cell and compen-
sated. It thus has no inuence on the measured value.
Measuring system
Pressure types

10
3 Product description
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
Absolute pressure: the measuring cell contains vacuum and is
encapsulated. The ambient pressure is not compensated and does
hence inuence the measured value.
The measuring system is completely welded and thus sealed against
the process.
The process tting is sealed against the process by a suitable seal. It
must be provided by the customer, depending on the process tting
also included in the scope of delivery, see chapter " Technical data", "
Materials and weights".
3.3 Supplementary cleaning procedures
The VEGABAR 81 is also available in the version " Oil, grease and
silicone-free". These instruments have passed through a special
cleaning procedure to remove oil, grease and paint-wetting impair-
ment substances (PWIS).
The cleaning is carried out on all wetted parts as well as on surfaces
accessible from outside. To keep the purity level, the instruments are
immediately packed in plastic foil after the cleaning process. The
purity level remains as long as the instrument is kept in the closed
original packaging.
Caution:
The VEGABAR 81 in this version may not be used in oxygen ap-
plications. For this purpose, instruments are available in the special
version " Oil, grease and silicone-free for oxygen applications".
3.4 Packaging, transport and storage
Your instrument was protected by packaging during transport. Its
capacity to handle normal loads during transport is assured by a test
based on ISO 4180.
The packaging consists of environment-friendly, recyclable card-
board. For special versions, PE foam or PE foil is also used. Dispose
of the packaging material via specialised recycling companies.
Transport must be carried out in due consideration of the notes on the
transport packaging. Nonobservance of these instructions can cause
damage to the device.
The delivery must be checked for completeness and possible transit
damage immediately at receipt. Ascertained transit damage or con-
cealed defects must be appropriately dealt with.
Up to the time of installation, the packages must be left closed and
stored according to the orientation and storage markings on the
outside.
Unless otherwise indicated, the packages must be stored only under
the following conditions:
• Not in the open
• Dry and dust free
Seal concept
Packaging
Transport
Transport inspection
Storage

11
3 Product description
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
• Not exposed to corrosive media
• Protected against solar radiation
• Avoiding mechanical shock and vibration
• Storage and transport temperature see chapter " Supplement -
Technical data - Ambient conditions"
• Relative moisture 20 … 85 %
With instrument weights of more than 18 kg (39.68 lbs) suitable and
approved equipment must be used for lifting and carrying.
3.5 Accessories
The instructions for the listed accessories can be found in the down-
load area on our homepage.
The protective cover protects the sensor housing against soiling and
intense heat from solar radiation.
Screwed anges are available in dierent versions according to the
following standards: DIN 2501, EN 1092-1, BS 10, ASME B 16.5,
JIS B 2210-1984, GOST 12821-80.
Welded sockets are used to connect the devices to the process.
Threaded and hygienic adapters enable simple adaptation of devices
with standard threaded ttings to process-side hygiene connections.
Storage and transport
temperature
Lifting and carrying
Protective cover
Flanges
Welded socket, threaded
and hygienic adapter

12
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
4 Mounting
4.1 General instructions
Note:
For safety reasons, the instrument must only be operated within the
permissible process conditions. You can nd detailed information on
the process conditions in chapter " Technical data" of the operating
instructions or on the type label.
Hence make sure before mounting that all parts of the instrument ex-
posed to the process are suitable for the existing process conditions.
These are mainly:
• Active measuring component
• Process tting
• Process seal
Process conditions in particular are:
• Process pressure
• Process temperature
• Chemical properties of the medium
• Abrasion and mechanical inuences
Protect your instrument against moisture ingress through the following
measures:
• Use a suitable connection cable (see chapter " Connecting to
power supply")
• Tighten the cable gland or plug connector
• Lead the connection cable downward in front of the cable entry or
plug connector
This applies mainly to outdoor installations, in areas where high
humidity is expected (e.g. through cleaning processes) and on cooled
or heated vessels.
Note:
Make sure that during installation or maintenance no moisture or dirt
can get inside the instrument.
To maintain the housing protection, make sure that the housing lid is
closed during operation and locked, if necessary.
Devices with threaded tting are screwed into the process tting with
a suitable wrench via the hexagon.
See chapter " Dimensions" for wrench size.
Warning:
The housing or the electrical connection may not be used for screw-
ing in! Depending on the device version, tightening can cause dam-
age, e. g. to the rotation mechanism of the housing.
Avoid damages on the device by lateral forces, for example by vibra-
tions. It is thus recommended to x the devices with process tting
Process conditions
Protection against mois-
ture
Screwing in
Vibrations

13
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
thread G½ of plastic at the installation site via a suitable measuring
instrument holder.
If there is strong vibration at the mounting location, the instrument
version with external housing should be used. See chapter " External
housing".
The permissible process pressure range is specied by "MWP" (Maxi-
mum Working Pressure) on the type label, see chapter " Structure".
The MWP takes the element of the measuring cell and processing
tting combination with the weakest pressure into consideration and
may applied permanently. The specication refers to a reference
temperature of +20 °C (+68 °F). It also applies when a measuring cell
with a higher measuring range than the permissible pressure range of
the process tting is installed order-related.
In addition, a temperature derating of the process tting, e. g. with
anges, can limit the permissible process pressure range according
to the respective standard.
Note:
In order to prevent damage to the device, a test pressure may only
exceed the specied MWP briey by 1.5 times at reference tempera-
ture. The pressure stage of the process tting as well as the overload
resistance of the measuring cell are taken into consideration here
(see chapter " Technical Data").
The permissible process pressure range is stated on the type label.
The instrument should only be operated with these pressures if the
mounting accessory used also fulls these values. This should be en-
sured by suitable anges, welded sockets, tension rings with Clamp
connections, sealings, etc.
Higher process temperatures often mean also higher ambient
temperatures. Make sure that the upper temperature limits stated in
chapter " Technical data" for the environment of the electronics hous-
ing and connection cable are not exceeded.
1
2
Fig. 4: Temperature ranges
1 Process temperature
2 Ambient temperature
Permissible process
pressure (MWP) - Device
Permissible process
pressure (MWP) - Mount-
ing accessory
Temperature limits

14
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
4.2 Instructions for oxygen applications
Warning:
As an oxidising agent, oxygen can cause or intensify res. Oils,
grease, some plastics and dirt can burn explosively on contact with
oxygen. There is a risk of serious personal injury or damage to prop-
erty.
Therefore, to avoid this, take the following precautions, for example:
• All components of the system - measuring instruments - must
be cleaned in accordance with the requirements of recognized
regulations or standards
• Depending on the seal material, certain temperatures and pres-
sures must not be exceeded in oxygen applications, see chapter "
Technical data"
• Devices for oxygen applications may only be unpacked from the
PE foil just before assembly.
• Check whether the marking "O2" is visible on the process tting
after removing the protection for the process tting
• Avoid any ingress of oil, grease and dirt
4.3 Ventilation and pressure compensation
The lter element in the electronics housing has the following func-
tions:
• Ventilation of the electronics housing
• Atmospheric pressure compensation (with relative pressure meas-
uring ranges)
Caution:
The lter element causes a time-delayed pressure compensation.
When quickly opening/closing the housing cover, the measured value
can change for approx. 5 s by up to 15 mbar.
For an eective ventilation, the lter element must be always free from
buildup. In case of horizontal mounting, turn the housing so that the
lter element points downward after the instrument is installed. This
provides better protection against buildup.
Caution:
Do not use a high-pressure cleaner. The lter element could be dam-
aged, which would allow moisture into the housing.
The following paragraphs describe how the lter element is arranged
in the dierent instrument versions.
Filter element - Function

15
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
1 2 3
4 4 4
Fig. 5: Position of the lter element - non-Ex, Ex ia version
1 Plastic, stainless steel housing (precision casting)
2 Aluminium housing
3 Stainless steel housing (electropolished)
4 Filter element
With the following instruments a blind plug is installed instead of the
lter element:
• Instruments in protection IP66/IP68 (1 bar) - ventilation via capillar-
ies in non-detachable cable
• Instruments with absolute pressure
→ Turn the metal ring in such a way that the lter element points
downward after installation of the instrument. This provides better
protection against buildup.
1
2
Fig. 6: Position of the lter element - Ex d version
1 Rotatable metal ring
2 Filter element
Instruments with absolute pressure have a blind plug mounted
instead of the lter element.
The process assembly of instruments with Second Line of Defense
(gastight leadthrough) is completely encapsulated. An absolute pres-
sure measuring cell is used so that no ventilation is required.
Filter element - Position
Filter element - Position
Ex d version
Instruments with Second
Line of Defense

16
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
1
2
Fig. 7: Position of the lter element - gastight leadthrough
1 Filter element
1
Fig. 8: Position of the lter element - IP69K version
1 Filter element
Instruments with absolute pressure have a blind plug mounted
instead of the lter element.
4.4 Combination Primary - Secondary
In principle, any sensor combination within the instrument series is
allowed. The following requirements must be fullled:
• Conguration of the sensor suitable for electronic dierential pres-
sure
• Pressure type is identical for both sensors, i.e. relative pressure/
relative pressure or absolute pressure/absolute pressure
• Primary Device measures the higher pressure
• Measurement setup as shown in the following chapters
The measuring range of each sensor is selected such that it ts the
measuring loop. For this, the max. recommended turn down must be
noted. See chapter " Technical data". It is absolutely necessary the
the measuring ranges of Primary and Secondary Device correspond.
Measurement result = Measured value of Primary (total pres-
sure) - measured value of Secondary (static pressure)
Depending on the application, individual combinations can result, see
following examples:
Data
Application: Level measurement
Medium: Water
Filter element - Position
IP69K version
Example - large vessel

17
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
Vessel height: 12 m, hydrostatic pressure = 12 m x 1000 kg/m3x
9.81 m/s2 = 117.7 kPa = 1.18 bar
Superimposed pressure: 1 bar
Total pressure: 1.18 bar + 1 bar = 2.18 bar
Instrument selection
Nominal measuring range Primary: 2.5 bar
Nominal measuring range Secondary: 1 bar
Turn Down: 2.5 bar/1.18 bar = 2.1 : 1
Data
Application: Level measurement
Medium: Water
Vessel height: 500 mm, hydrostatic pressure = 0.50 m x 1000 kg/m3x
9.81 m/s2 = 4.9 kPa = 0.049 bar
Superimposed pressure: 350 mbar = 0.35 bar
Total pressure: 0.049 bar + 0.35 bar = 0.399 bar
Instrument selection
Nominal measuring range Primary: 0.4 bar
Nominal measuring range Secondary: 0.4 bar
Turn Down: 0.4 bar /0.049 bar = 8.2 : 1
Data
Application: Dierential pressure measurement
Medium: Gas
Static pressure: 0.8 bar
Dierential pressure on orice: 50 mbar = 0.050 bar
Total pressure: 0.8 bar + 0.05 bar = 0.85 bar
Instrument selection
Nominal measuring range Primary: 1 bar
Nominal measuring range Secondary: 1 bar
Turn Down: 1 bar/0.050 bar = 20 : 1
The measuring result (level, pressure dierence) as well as measured
value Secondary (static or superimposed pressure) are output by the
sensor. Depending on the instrument version, output as 4 … 20 mA
signal or digitally via HART, Probus PA or Foundation Fieldbus.
To reach the Safety Integrity Level (SIL) for the electronic dierential
pressure, both instruments must be SIL-qualied.
4.5 Level measurement
Keep the following in mind when setting up the measuring system:
• Mount the Primary Device below the min. level
• Mount primary device away from emptying
• Mount the Primary Device so that it is protected against pressure
shocks from the stirrer
Example - small vessel
Example-oricein
pipeline
Output measured values
Measurement setup

18
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
• Mount the Secondary Device above the max. level
• Mount secondary device away from lling stream
1
2
Fig. 9: Measurement setup, level measurement in pressurized vessel
1 VEGABAR 81, Primary Device
2 VEGABAR 81, Secondary Device
4.6 Dierentialpressuremeasurement
Take note of the following instructions for the measurement setup, for
example in gases:
• Mount the instruments above the measuring point
Possible condensation can then drain o into the process line.
Measurement setup

19
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
12
Fig. 10: Measurement setup for dierential pressure measurement of gases in
pipelines
1 VEGABAR 81, Primary Device
2 VEGABAR 81, Secondary Device
4.7 Interface measurement
Requirements for a functioning measurement are:
• Vessel with changing level
• Products with steady density
• Interface always between the measurement points
• Total level always above the upper measurement point
The mounting distance " h" of the two sensors should be at least
10 %, better 20 %, of the nal value of the sensor measuring range. A
bigger distance increases the accuracy of the interface measurement.
Measurement setup

20
4 Mounting
VEGABAR 81 • Secondary Device for electronic dierential pressure
48045-EN-230914
h
1,0
0,8
1
2
Fig. 11: Measurement setup with interface measurement, h = distance between
the two measuring points
1 VEGABAR 81, Primary Device
2 VEGABAR 81, Secondary Device
Note:
The interface measurement is possible in open as well as in closed
vessels.
4.8 Density measurement
Requirements for a functioning measurement are:
• Vessel with changing level
• Distance between the measurement points as large as possible
• Level always above the upper measuring point
Measurement setup