Flexim FLUXUS F401 User manual

FLUXUS F401
UMFLUXUS_F401V2-1EN
Operating instruction

FLEXIM GmbH
Boxberger Straße 4
12681 Berlin
Germany
Tel.: [phone]
Fax: [phone]
E-mail: [email protected]
www.flexim.com
FLUXUS is a registered trademark of FLEXIM GmbH.
Operating instruction for
FLUXUS F401
UMFLUXUS_F401V2-1EN, 2020-06-12
Article number: 21661
Copyright (©) FLEXIM GmbH 2020
Subject to change without prior notice.

FLUXUS F401 Table of contents
Table of contents
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1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.1 General safety instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 Intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 Not intended use . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4 Safety instructions for the user . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.5 Safety instructions for the operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6 Safety instructions for electrical work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.7 Safety instructions for transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.8 Recommended procedure in hazardous situations . . . . . . . . . . . . . . . . . . . . . 12
3 General principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Measurement principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Measurement arrangements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.3 Acoustic penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.4 Undisturbed flow profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
4 Product description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.1 Measuring system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.2 Handling concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.3 Navigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.4 Keyboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
5 Transport and storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.1 Transport . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.2 Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
6 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.1 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
6.2 Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
7 Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.1 Transducers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
7.2 Power supply . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
7.3 Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
7.4 Connection of the RS232 service interface . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

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8 Start-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.1 Start-up settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
8.2 Switching on/off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
8.3 Program branches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
8.4 HotCodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
8.5 Language . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.6 Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
8.7 Time and date . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.8 Instrument information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
9 Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.1 Parameter input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
9.2 Measurement settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
9.3 Start of the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
9.4 Display of measured values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
9.5 Execution of special functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
9.6 Determination of the flow direction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
9.7 Stop of the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
10 Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
10.1 Problems with the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
10.2 Measuring point selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
10.3 Maximum acoustic contact . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
10.4 Application-specific problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
10.5 Significant deviations of the measured values . . . . . . . . . . . . . . . . . . . . . . . . 79
10.6 Problems with the totalizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
11 Maintenance and cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
11.1 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
11.2 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81
12 Dismounting and disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
12.1 Dismounting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
12.2 Disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
13 Outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
13.1 Installation of a binary output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
13.2 Activation of a binary output as pulse output . . . . . . . . . . . . . . . . . . . . . . . . . . 85

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14 Data logger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
14.1 Activation/Deactivation of the data logger . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
14.2 Setting the storage rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
14.3 Configuration of the data logger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
14.4 Measurement with activated data logger . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
14.5 Deletion of measured values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
14.6 Information relating the data logger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
15 Data transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
15.1 FluxDiagReader/FluxDiag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
15.2 Terminal program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
15.3 Transmission parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
15.4 Data format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
15.5 Data structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
16 Advanced functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
16.1 Low-power mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
16.2 Night-flow mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
16.3 Totalizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
16.4 NoiseTrek parallel beam mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
16.5 Upper limit of the flow velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
16.6 Cut-off flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
16.7 Profile correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
16.8 Uncorrected flow velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
16.9 Diagnosis with the help of the snap function . . . . . . . . . . . . . . . . . . . . . . . . . 111
16.10 Activation of a binary output as alarm output . . . . . . . . . . . . . . . . . . . . . . . . 112
16.11 Behavior of the alarm outputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

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17 SuperUser mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
17.1 Activation/deactivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
17.2 Defining flow parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
17.3 Setting of the measuring time in the low-power mode . . . . . . . . . . . . . . . . . . 124
17.4 Setting of measuring cycles in the night-flow mode . . . . . . . . . . . . . . . . . . . 124
17.5 Limit of the signal amplification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
17.6 Upper limit of the sound speed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
17.7 Detection of long measurement failures . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
17.8 Number of decimal places of the totalizers . . . . . . . . . . . . . . . . . . . . . . . . . . 128
17.9 Manual reset of the totalizers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
17.10 Display of the totalizer sum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
17.11 Display of the last valid measured value . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130
17.12 Displays during the measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
18 Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
18.1 Dialogs and menus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
18.2 Measurement settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
18.3 Contrast settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
18.4 Program code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
Annex
A Menu structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
B Units of measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
C Reference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
D Conformity declarations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

1 Introduction
FLUXUS F401
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1 Introduction
This operating instruction has been written for users operating the ultrasonic flowmeter
FLUXUS. It contains important information about the measuring equipment, how to han-
dle it correctly, and how to avoid damages. Read the safety instructions carefully. Make
sure you have read and understood this operating instruction before using the measuring
equipment.
Any work on the measuring equipment has to be carried out by authorized and qualified
personnel in order to detect and avoid possible risks and dangers.
Presentation of warnings
This operating instruction contains warnings marked as follows:
Danger!
Type and source of danger
danger with high level of risk, which if not avoided, can lead to death or
serious injuries
→ measures of prevention
Warning!
Type and source of danger
danger with medium level of risk, which if not avoided, can lead to death
or serious injuries
→ measures of prevention
Caution!
Type and source of danger
danger with low level of risk, which if not avoided, can lead to minor or
moderate injuries
→ measures of prevention
Important!
This text contains important information which should be observed to avoid material
damage.

1 Introduction
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Storage of the operational manual
The operating instruction must permanently be available at the place where the measur-
ing equipment is used. It must always be available to the user.
User comments
All reasonable effort has been made to ensure the correctness of the content of this oper-
ating instruction. If you however find some erroneous information or miss information,
please inform us.
We will be grateful for any suggestions and comments regarding the concept and your
experience working with the measuring equipment. If you have any suggestions about
improving the documentation and particularly this operating instruction, please let us
know so that we can consider your comments for future reprints.
Copyright
The contents of this operating instruction are subject to changes without prior notice. All
rights reserved. No part of this operating instruction may be reproduced in any form with-
out FLEXIM's written permission.
Notice!
This text contains important information about the handling of the measuring equip-
ment.

2 Safety instructions
FLUXUS F401 2.1 General safety instructions
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2 Safety instructions
2.1 General safety instructions
Prior to any work, read the operating instruction carefully and in full.
Failure to comply with the instructions, in particular with the safety instructions, poses a
risk to health and can lead to material damages. For further information, contact FLEXIM.
During installation and operation of the measuring equipment, observe the ambient and
installation conditions specified in the documentation.
The measuring equipment has to be checked for proper condition and operational safety
before each use. If troubles or damages have occurred during installation or operation of
the measuring equipment, please inform FLEXIM.
It is not allowed to make unauthorized modifications or alterations to the measuring equip-
ment.
The personnel has to be suitably trained and experienced for the work.
2.2 Intended use
The measuring equipment is intended for the measurement of fluid properties in closed
pipes. By means of connected transducers, the transit times of the ultrasonic signals in
the fluid and the pipe are measured and evaluated.
The transmitter uses these values to calculate the sought quantities, e.g., volumetric flow
rate, mass flow rate, heat quantity, density and concentration. Through comparison with
the values stored in the transmitter further physical quantities can be determined. The
physical quantities are provided via configurable outputs and the display.
• All instructions of this operating instruction have to be observed to ensure intended use.
• Any use beyond or other than the intended use is not covered by warranty and can
present a danger. Any damage arising from not intended use shall be solely the liability
of the operator or user.
• The measurement is carried out without direct contact to the fluid in the pipe. The flow
profile is not influenced.
• The transducers are fixed to the pipe using the supplied transducer mounting fixture.
• Observe the operating conditions, e.g., environment, voltage ranges. For the technical
data of the transmitter, transducers and accessories, see technical specification.

2 Safety instructions
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2.3 Not intended use
Not intended use in terms of a misuse means:
• any work on the measuring equipment without observing all instructions in this operat-
ing instruction
• use of transmitter, transducer and accessories combinations not intended by FLEXIM
• installation of the transmitter, transducers and accessories in explosive atmospheres
they are not approved for
• any work on the measuring equipment (e.g., installation, dismounting, connection, start-
up, operation, service and maintenance) carried out by unauthorized and untrained per-
sonnel
• storage, installation and operation of the measuring equipment outside the specified
ambient conditions, see technical specification
2.4 Safety instructions for the user
Any work on the transmitter has to be carried out by authorized and qualified personnel.
Observe the safety instructions in the operating instruction. For the technical data of the
transmitter, transducers and accessories, see technical specification.
• Observe the safety and accident prevention regulations applicable on the site of operation.
• Only use the supplied mounting fixtures and transducers as well as the intended acces-
sories.
• Always wear the required personal protective equipment.
2.5 Safety instructions for the operator
• The operator shall qualify the personnel to perform their assigned tasks. The operator
shall provide the required personal protective equipment and oblige the personnel to
wear it. It is recommended to risk assess the workplace.
• Besides the safety instructions in this operating instruction, the health, safety and envi-
ronment regulations applicable for the range of application of the transmitter, transduc-
ers and accessories have to be observed.
• With the exceptions stated in chapter 11, the measuring equipment is maintenance-
free. Any components and spare parts may only be replaced by FLEXIM. The operator
shall carry out periodic checks for changes or damages that can present a danger. For
further information, contact FLEXIM.
• Observe the specifications for the installation and connection of the transmitter, trans-
ducers and accessories, see chapter 6 and 7.

2 Safety instructions
FLUXUS F401 2.6 Safety instructions for electrical work
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2.6 Safety instructions for electrical work
• Electrical work may only be carried out if there is enough space.
• The degree of protection of the transmitter is only ensured if the cables are firmly con-
nected to the transmitter and all unused connections are covered.
• The condition and tight fit of the electrical connections have to be checked at regular in-
tervals.
• The power supply unit for charging the battery may only be connected to networks up to
overvoltage category II. Use only the supplied power supply unit. For the power supply
via power cable and power adapter, observe the safety instructions in chapter 7, sec-
tion 7.2.
• The transmitter and the power supply unit must not be disassembled, see Fig. 2.1. The
transmitter does not contain any components to be maintained by the user. For repair
and service work, please contact FLEXIM.
• Observe the safety and accident prevention regulations for electrical systems and
equipment.
Fig. 2.1: Transmitter

2 Safety instructions
2.7 Safety instructions for transport FLUXUS F401
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2.7 Safety instructions for transport
• If you detect a transport damage when unpacking the delivery, please contact the sup-
plier or FLEXIM immediately.
• The transmitter is a sensitive electronic measuring instrument. Avoid shocks or impacts.
• Handle the transducer cable with care. Avoid excessive bending or buckling. Observe
the ambient conditions.
• Select a solid surface to put the transmitter, transducers and accessories on.
• The transmitter, transducers and accessories have to be properly packed for transport:
– Use, if possible, the original packaging by FLEXIM or an equivalent cardboard box.
– Position the transmitter, transducers and accessories in the middle of the cardboard
box.
– Fill any voids with appropriate packaging material (e.g., paper, foam, bubble wrap).
– Protect the cardboard box against humidity.
2.8 Recommended procedure in hazardous situations
Fire fighting measures
• If possible, disconnect the transmitter from the power supply.
• Prior to extinguishing, protect any electrical parts that are not affected by the fire (e.g.,
using a cover).
• Select a suitable extinguishing agent. Avoid, if possible, conductive extinguishing
agents.
• Observe the applicable minimum distances. The minimum distances differ depending
on the used extinguishing agent.

3 General principles
FLUXUS F401 3.1 Measurement principle
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3 General principles
In the ultrasonic flow measurement, the flow velocity of the fluid in a pipe is determined.
Further physical quantities are derived from the flow velocity and from additional physical
quantities, if necessary.
3.1 Measurement principle
The flow velocity of the fluid is measured using the transit time difference correlation prin-
ciple.
3.1.1 Terms
Flow profile
Distribution of flow velocities over the cross-sectional pipe area. For an optimal measure-
ment, the flow profile has to be fully developed and axisymmetrical. The shape of the flow
profile depends on whether the flow is laminar or turbulent and is influenced by the condi-
tions at the inlet of the measuring point.
Reynolds number Re
Coefficient describing the turbulence behavior of a fluid in the pipe. The Reynolds number
Re is calculated from the flow velocity, the kinematic viscosity of the fluid and the inner
pipe diameter.
If the Reynolds number exceeds a critical value (usually approx. 2300, if the fluid flows in
a pipe), a transition from a laminar flow to a turbulent flow takes place.
Laminar flow
A flow without any turbulence. There is no mixing between the parallel flowing layers of
the fluid.
Turbulent flow
A flow with turbulences (swirling of the fluid). In technical applications, the flow in the pipe
is mostly turbulent.
Transition range
The flow is partly laminar and partly turbulent.
Sound speed c
Speed of the propagating sound. The sound speed depends on the mechanical proper-
ties of the fluid or the pipe material. In pipe materials and other solid materials, a distinc-
tion is made between the longitudinal and transversal sound speed. For the sound speed
of some fluids and materials, see annex C.
Flow velocity v
Average value of all flow velocities of the fluid over the cross-sectional pipe area.

3 General principles
3.1 Measurement principle FLUXUS F401
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Acoustic calibration factor ka
ka =
The acoustic calibration factor ka is a transducer parameter which results from the sound
speed c within the transducer and the angle of incidence. According to Snell's law of re-
fraction, the angle of propagation in the adjoining fluid or pipe material is:
ka = = =
Fluid mechanics correction factor kRe
With the fluid mechanics calibration factor kRe, the measured value of the flow velocity in
the area of the sound beam is converted into the value of the flow velocity across the
whole cross-sectional pipe area. In case of a fully developed flow profile, the fluid me-
chanics calibration factor only depends on the Reynolds number and the roughness of
the inner pipe wall. The fluid mechanics calibration factor is recalculated by the transmit-
ter for each new measurement.
Volumetric flow rate
= v · A
The volume of the fluid that passes through the pipe per unit time. The volumetric flow
rate is calculated from the product of the flow velocity v and the cross-sectional pipe area
A.
Mass flow rate
= · ρ
The mass of the fluid that passes through the pipe per unit time. The mass flow rate is
calculated from the product of the volumetric flow rate and the density ρ.
c
sin
------------
c
sin
------------ c
sin
------------ c
sin
-----------
V
·
V
·
m
·
m
·V
·
V
·

3 General principles
FLUXUS F401 3.1 Measurement principle
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UMFLUXUS_F401V2-1EN, 2020-06-12
3.1.2 Measurement of the flow velocity in the TransitTime mode
The signals are emitted and received by 2 transducers alternatively in and against the
flow direction. If the fluid is flowing, the signals propagating in the fluid are displaced with
the flow.
Caused by this displacement, the sound path of the signal in flow direction is reduced
and the signal against the flow direction is increased, see Fig. 3.1 and Fig. 3.2.
This causes a change in the transit times. The transit time of the signal in flow direction is
shorter than the transit time against the flow direction. The transit time difference is pro-
portional to the average flow velocity.
The average flow velocity of the fluid is calculated as follows:
v = kRe · ka ·
where
v – average flow velocity of the fluid
kRe – fluid mechanics calibration factor
ka– acoustic calibration factor
Δt – transit time difference
tγ– transit time in the fluid
Fig. 3.1: Sound path of the signal in the flow direction
c – sound speed
1 – transducer (emitter)
2 – transducer (receiver)
3 – pipe wall
t
2 t

-----------
cβ
β
α
γcγ
3
21
cαcαreduction of the
sound path
flow direction of
the fluid
sound path with flow
sound path
without flow

3 General principles
3.1 Measurement principle FLUXUS F401
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Fig. 3.2: Sound path of the signal against the flow direction
c – sound speed
1 – transducer (emitter)
2 – transducer (receiver)
3 – pipe wall
Fig. 3.3: Transit time difference Δt
1 – signal in the flow direction
2 – signal against the flow direction
cβ
flow direction of
the fluid
sound path with flow
sound path
without flow
β
α
γ
cγ
increase of the
sound path 3
12
cαcα
1 2
Δt

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FLUXUS F401 3.1 Measurement principle
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3.1.3 Measurement of the flow velocity in the NoiseTrek parallel beam
mode
Pipes with a small pipe diameter or fluids which strongly attenuate the ultrasonic signal
can cause a reduction of the transit time in the fluid with the result that the signal quality
is no longer sufficient. In this case the NoiseTrek parallel beam mode has to be used.
The NoiseTrek parallel beam mode uses the presence of gas bubbles and/or solid parti-
cles in the fluid.
Ultrasonic signals are sent into the fluid at short intervals, reflected by the gas bubbles
and/or the solids particles and again received. This leads to a better signal quality. The
transducers are mounted in parallel on the pipe at a small distance, see Fig. 3.4.
A measurement in TransitTime mode is not possible when working with this measure-
ment arrangement.
The transit time difference t of 2 consecutive ultrasonic signals is determined. It be-
haves proportionately to the distance the gas bubble/solid particle is covering between 2
consecutive pulses and thus, to the average flow velocity of the fluid, see Fig. 3.5.
Fig. 3.4: Measurement arrangement in the NoiseTrek parallel beam mode
Fig. 3.5: Measurement of the flow velocity in the NoiseTrek parallel beam mode
flow direction
transducers transducers
flow direction
ultrasonic signal S1
gas bubble or
solids particle
ultrasonic signal S2
pulse at time t
gas bubble or
solids particle
pulse at time t + Δtp
transit time t1transit time t2

3 General principles
3.2 Measurement arrangements FLUXUS F401
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The average flow velocity of the fluid is calculated as follows:
v=kRe · ka·
where
3.2 Measurement arrangements
3.2.1 Terms
Sound path
The distance covered by the ultrasonic signal after crossing the pipe once. The number
of the sound paths is:
• odd if the measurement is carried out in diagonal arrangement
• even if the measurement is carried out in reflection arrangement
v – average flow velocity of the fluid
kRe – fluid mechanics calibration factor
ka– acoustic calibration factor
Δtp– time difference between 2 consecutive pulses
Δt – transit time difference of ultrasonic signals S1 and S2 (Δt = t2 - t1)
Diagonal arrangement Reflection arrangement
The transducers are mounted on opposite
sides of the pipe.
The transducers are mounted on the same
side of the pipe.
t
2tp

----------------

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FLUXUS F401 3.2 Measurement arrangements
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Beam
The path covered by the ultrasonic signal between the transducers, i.e., the transducer
emitting the ultrasonic signal and the transducer receiving it. One beam consists of 1 or
several sound paths.
Transducer distance
The transducer distance is measured between the inner edges of the transducers.
Fig. 3.6: Diagonal arrangement with
1 beam and 3 sound paths
Fig. 3.7: Reflection arrangement with
1 beam and 4 sound paths
reflection arrangement
diagonal arrangement
(positive transducer distance)
diagonal arrangement
(negative transducer distance)
a – transducer distance
a
a
a

3 General principles
3.2 Measurement arrangements FLUXUS F401
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Sound beam plane
plane, containing sound paths or beams
3.2.2 Examples
Fig. 3.8: 2 sound paths in 1 plane
Diagonal arrangement with 1 beam Reflection arrangement with 1 beam
1 transducer pair
1 sound path
1 transducer pair
2 sound paths