Teledyne 2151P Operating instructions

2151P Area Velocity
Flow System
Installation and Operation Guide
Part #69-2003-247 of Assembly #60-2004-230
Copyright © 2002. All rights reserved, Teledyne Isco
Revision W, October 2013

Foreword
This instruction manual is designed to help you gain a thorough understanding of the operation of
the equipment. Teledyne Isco recommends that you read this manual completely before placing the
equipment in service.
Although Teledyne Isco designs reliability into all equipment, there is always the possibility of a
malfunction. This manual may help in diagnosing and repairing the malfunction.
If a problem persists, call or e-mail the Teledyne Isco Technical Service Department for assistance.
Simple difficulties can often be diagnosed over the phone.
If it is necessary to return the equipment to the factory for service, please follow the shipping
instructions provided by the Customer Service Department, including the use of the Return
Authorization Number specified. Be sure to include a note describing the malfunction. This
will aid in the prompt repair and return of the equipment.
Teledyne Isco welcomes suggestions that would improve the information presented in this manual
or enhance the operation of the equipment itself.
Teledyne Isco is continually improving its products and reserves the right to change product
specifications, replacement parts, schematics, and instructions without notice.
Contact Information
Customer Service
Phone: [phone] (USA, Canada, Mexico)
[phone] (Outside North America)
Fax: [phone]
Email: [email protected]
Technical Support
Phone: Toll Free [phone] (Samplers and Flow Meters)
Toll Free [phone] (Syringe Pumps and Liquid Chromatography)
Email: [email protected]
Return equipment to: 4700 Superior Street, Lincoln, NE 68504-1398
Other Correspondence
Mail to: P.O. Box 82531, Lincoln, NE 68501-2531
Email: [email protected]
Revised September 2012

v
Important Safety Information
DANGER
If Isco’s 2151P Intrinsically Safe Area Velocity Flow System is installed in a hazardous area, it MUST
be installed in accordance with control drawing 60-2003-227, shown on the following pages, and in
accordance with the requirements of the authority that has jurisdiction for the installation of
equipment in hazardous areas at your specific installation site.
The certified control drawing details the only approved method of installing the 2151P area velocity
flow system in a hazardous area. Where specific Isco part numbers appear, they represent the only
approved equipment certified to be used with the 2151P. Any equipment substitutions or installations
not specifically detailed on the control drawing will automatically void the intrinsically safe certifi-
cation of the 2151P and could result in fire or explosion!
Detailed hazardous area installation instructions for the 2151P are provided in Section 2 of this
manual. Read this section carefully before beginning equipment installation! General safety infor-
mation for working in confined spaces is provided in Appendix E.
The 2151P is listed as intrinsically safe for Class I, Div. 1, Groups C and D hazardous locations. This
means that when it is properly installed in a Class I, Div. 1, Group C or D hazardous location, the
circuits within the 2151P are designed to be incapable of producing a spark or thermal effect that
could ignite a mixture of flammable or combustible gases. This does not mean that the 2151P is
explosion proof. If the equipment is not installed properly in a hazardous area, or if proper safety pre-
cautions are not followed, there is a serious potential for an explosion. Carefully review the safety
information, control drawing, and installation requirements and procedures before installing the
2151P!

vi
Safetyard Sy mbols
Hazard Symbols This manual uses symbols to warn of hazards. The symbols are
explained below.
Hazard Severity Levels This manual applies Hazard Severity Levels to the safety alerts,
These three levels are described in the sample alerts below.
CAUTION
Cautions identify a potential hazard, which if not avoided, may
result in minor or moderate injury. This category can also warn
you of unsafe practices, or conditions that may cause property
damage.
WARNING
Warnings identify a potentially hazardous condition, which
if not avoided, could result in death or serious injury.
DANGER
Danger is limited to the most extreme situations
to identify an imminent hazard, which if not
avoided, will result in death or serious injury.
Hazard Symbols
Warnings and Cautions
The exclamation point within the triangle is a warning sign alerting you of
important instructions in the instrument’s technical reference manual.
Symboles de sécurité
Ce symbole signale l’existence d’instructions importantes relatives au
produit dans ce manuel.
Warnungen und Vorsichtshinweise
Das Ausrufezeichen in Dreieck ist ein Warnzeichen, das Sie darauf
aufmerksam macht, daß wichtige Anleitungen zu diesem Handbuch
gehören.
Advertencias y Precauciones
Esta señal le advierte sobre la importancia de las instrucciones del manual
que acompañan a este producto.

vii
General Warnings Before installing, operating, or maintaining the 2151P system, it
is imperative that all hazards and preventive measures are
understood. Be sure to read all safety information contained in
this manual, in addition to the installation instructions in Sec-
tion 2.
While specific hazards may vary according to location and appli-
cation, take heed of the following general warnings:
WARNING
Avoid hazardous practices! If you use these instruments in
any way not specified in this manual, the protection
provided by the instruments may be impaired; this will
increase your risk of injury.
AVERTISSEMENT
Eviter les manipulations hasardeuses! Si vous utilisez ces
appareils de façon non conforme au mode d’emploi, vous
risquez des blessures graves.
WARNING
The installation and use of this product may subject you to
hazardous working conditions that can cause you serious
or fatal injuries. Take any necessary precautions before
entering a worksite. Install and operate this product in
accordance with all applicable safety and health
regulations, and local ordinances.
L’installation de ces instruments peut vous entrainer à
travailler dans des conditions précaires et risquées pou-
vant entrainer de graves blessures.Veuillez respecter
toutes les conditions requises de sécurité avant de péné-
trer dans un regard ou sur le site concerné. Installer et
manipuler l’instrument selon les règles ou la législation
en vigueur concernant la sécurité et la protection des
individus.

viii

ix
2151P Area Velocity Flow System
Table of Contents
Section 1 Introduction
1.1 Product Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1
1.2 2151P System Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2.1 Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2.2 Velocity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2
1.2.3 Flow Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.4 Total Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.2.5 Data Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3
1.3 Identifying Module Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1.4 Technical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
Section 2 Preparation and Installation
2.1 Unpacking Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.2 Preparing for Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1
2.2.1 Locating the Site . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.2.2 Channels Without a Primary Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.2.3 Channels With a Primary Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-2
2.2.4 2151P and AV Sensor Mounting Considerations . . . . . . . . . . . . . . . . . . . . . 2-3
2.3 Installing the AV Sensor and 2151P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.1 Overview of Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.2 Install the AV Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3
2.3.3 Connecting the AV Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2.3.4 Mounting the 2151P . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6
2.3.5 Inspect the Desiccant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
2.4 Power and Network Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-10
2.4.1 Making Intrinsically Safe Wiring Connections . . . . . . . . . . . . . . . . . . . . . 2-14
2.4.2 Making Non-intrinsically Safe Wire Connections . . . . . . . . . . . . . . . . . . . 2-16
2.4.3 Connecting Using a Communication/
Barrier Cable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
2.5 Connecting to the Isco Quick Disconnect Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23
2.6 Program the Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24
2.7 Mounting Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
2.7.1 Spring Rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-25
2.7.2 Scissors Mounting Ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-27
2.7.3 Completing the AV Sensor Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29
2.8 Final Installation Check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-30
2.9 System Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-31
Section 3 Programming
3.1 Section Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.2 Flowlink Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.3 Program Settings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1
3.3.1 Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2
3.3.2 Zero Level Offset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.3.3 No Velocity Data and Flow Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
3.3.4 Flow Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

2151P Area Velocity Flow System
Table of Contents
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3.3.5 Silt Level . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.6 Data Storage Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-6
3.3.7 Site Name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
3.3.8 Module Name . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-7
Section 4 Modbus Protocol
4.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.2 Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1
4.2.1 Establishing Communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.2.2 Module Addressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-2
4.3 Configurations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
4.4 Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-4
4.5 Common Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
4.6 Register Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
Section 5 Maintenance
5.1 Maintenance Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.2 Maintenance Kit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1
5.3 Desiccant Maintenance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.3.1 Reactivating the Desiccant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2
5.4 Channel Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.5 Other Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.5.1 Hydrophobic Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.5.2 Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
5.5.3 Sensor Cable Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.6 How to Obtain Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
5.6.1 Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4
Appendix A Replacement Parts
A.1 Replacement Parts Diagrams and Listings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
Appendix B Accessories
B.1 How to Order. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
B.2 General Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1
B.3 AV Sensor Mounting Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2
Appendix C Material Safety Data Sheets
C.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Appendix D Safety Information
D.1 Safety Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1
D.2 General Safety Procedures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-1
D.3 Lethal Atmospheres in Sewers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . D-4
List of Figures
1-1 2151P System, Top Left View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1-2 2151P System, Top Right View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5
1-3 Components - 2151P Area Velocity Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1-4 2151P Area Velocity Flow System Communication Connector Pins . . . . . . . . . . . 1-9

2151P Area Velocity Flow System
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xi
2-1 Connecting the AV Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
2-2 Mounting the 2151P in a Typical Round-pipe Installation . . . . . . . . . . . . . . . . . . 2-7
2-3 Control Drawing of 2151P Area Velocity Flow System Installation, Page 1 . . . . 2-8
2-4 Control Drawing of 2151P Area Velocity Flow System Installation, Page 2 . . . . 2-9
2-5 Typical Round-pipe Installation Connected to
QD Box, 2108 Module, and 2101 Field Wizard with
Network Isolator P/N 60-2004-224 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11
2-6 Isolator and Barrier Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-12
2-7 Terminal Connections to the 2108 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-17
2-8 Typical Round-pipe Installation
Connected to a Laptop Computer With Cable P/N 60-2004-153 . . . . . . . . . . . . . 2-19
2-9 Intrinsically Safe Communication/Barrier
Cable For Connection to a Computer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
2-10 Entity Rated Power Barrier Connections
When 2151P is Connected to a Laptop
Computer Using Cable P/N 60-2004-153 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-20
2-11 Typical Round-pipe Installation
Connected to a 2101 Field Wizard With Cable P/N 60-2004-201 . . . . . . . . . . . . 2-22
2-12 Intrinsically Safe Communication/Barrier
Cable For Connection to a 2101 or 2103 Module . . . . . . . . . . . . . . . . . . . . . . . . . 2-23
2-13 Isco’s Quick Disconnect Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-23
2-14 Wiring Inside Quick Disconnect Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-24
2-15 Sensor Installed on a Spring Ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-26
2-16 Scissors Ring adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-28
3-1 Preferred Measurement Location . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3
3-2 Zero Level Offset Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-4
4-1 Configuration example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
List of Tables
1-1 2151P Area Velocity Flow System - Top Left View . . . . . . . . . . . . . . . . . . . . . . . . 1-4
1-2 2151P Area Velocity Flow System - Top Right View . . . . . . . . . . . . . . . . . . . . . . . 1-5
1-3 Components - 2151P Area Velocity Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-6
1-4 Specifications – 2151P Area Velocity Flow System Module . . . . . . . . . . . . . . . . . 1-7
1-5 Specifications – Area Velocity Sensor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-8
1-6 Communication Connector Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-9
2-1 Entity Rated Power Barrier
Intrinsically Safe Wire Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
2-2 Network Isolator
Intrinsically Safe Wire Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-14
2-3 Entity Rated Power Barrier
Non-Intrinsically Safe Wire Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16
2-4 Network Isolator
Non-Intrinsically Safe Wire Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16
2-5 Voltage Specifications for 2100 System Components . . . . . . . . . . . . . . . . . . . . . . 2-31
3-1 Flow Conversion Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

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1-1
2151P Area Velocity Flow System
Section 1 Introduction
1.1 Product Description The 2151P Intrinsically Safe Area Velocity Flow System is part
of Isco’s 2100 Series. The 2100 Series measures parameters of
open channel flow streams.
The 2151P is designed for permanent installation and uses a
power source located in a safe area.
Typical applications for the 2151P Area Velocity Flow System
include:
• Sewer Flow
• Level measurement in explosive or potentially explosive
areas, such as manholes, storage tanks, and digesters
• Measurement of shallow flows in small pipes
• Permanent flow monitoring
The 2151P Area Velocity Flow System is designed to be intrinsi-
cally safe, and allows installation of the module in Class I,
Division 1, and Groups C and D hazardous locations. The concept
of intrinsic safety is to limit the energy available to a given
circuit or device to a level where electrical discharge (sparking)
cannot ignite the hazardous (flammable or explosive) atmo-
sphere. With no spark ignition possible, safe operation of the
equipment in areas with hazardous atmospheres is possible.
The standard 2100 Series is designed to be modular so that you
can expand the system by stacking modules to meet your data
collection needs. Out of concern for your safety, the 2151P system
was designed to prevent you from stacking additional modules
onto the system.
The 2151P is connected to other 2100 Series modules using a
network barrier cable or Isco Network Isolator. (Refer to
Section 2 for installation drawings and instructions.)
The 2151P Area Velocity Flow System is paired with Isco’s
Flowlink for Windows software. With this full-featured appli-
cation software, you can quickly set up the module, retrieve mea-
surement data, manage the sites and analyze the data.
The 2151P’s data storage memory is quite flexible, able to store
the measurements in intervals from 15 seconds to 24 hours. The
module can also be configured for variable rate data storage.
Variable rates allow you to store data at a different interval
when a programmed condition occurs.
The module’s program and collected data are stored in Flash
memory for security. Flash memory retains data without the
concern of power failures. Its storage capacity is more than suffi-
cient for most applications. The data storage memory can hold

2151P Area Velocity Flow System
Section 1 Introduction
1-2
approximately 79,000 readings ñ the equivalent of nine months
of level and velocity data when stored at fifteen minute intervals.
The flash memory also stores sensor calibration information. A
separate flash memory device inside the module stores the oper-
ating firmware.
The rugged 2151P components are rated NEMA 4X, 6P (IP68).
The permanently sealed enclosures are designed to meet the
environmental demands of most sewer flow monitoring applica-
tions. All connections between sensors and communication cables
lock in place. Each locking mechanism strongly secures the com-
ponents and ensures a watertight seal.
1.2 2151P System
Overview
The 2151P measures liquid level and average stream velocity,
and calculates the flow rate and total flow. The liquid level and
velocity measurements are read from an attached Area Velocity
(AV) Sensor that is placed in the flow stream. Flow rate calcula-
tions are performed internally using the measured parameters
from the AV Sensor.
The 2151P is designed to provide durable operation with a
minimal amount of routine maintenance. Routine maintenance
can be performed in the field, while keeping hazardous location
restrictions in mind. Typically, the 2151P System and its AV
Sensor will only require that you keep the stream free from
excessive debris, and replace spent desiccant. Sections 1.2.1
through 1.2.5 describe the 2151P and sensor in greater detail.
1.2.1 Level The AV Sensor’s internal differential pressure transducer mea-
sures the liquid level. The transducer is a small piezo-resistive
chip that detects the difference of the pressures felt on the inner
and outer face.
The stainless steel outer diaphragm is exposed to the flow stream
through the ports under the AV Sensor. The pressure felt on the
outer diaphragm is transferred to the outer face of the trans-
ducer through a silicone fluid medium. The outer diaphragm and
fluid isolate the sensitive transducer from direct exposure to the
stream. The inner face of the transducer is exposed, or refer-
enced, to the atmosphere through the internal vent tube that
runs the full length of the AV Sensor’s cable.
The difference between the pressures exerted on the transducer
is the hydrostatic pressure. Hydrostatic pressure is proportional
to the level of the stream. The analog representation of the
hydrostatic pressure is digitized and sent to the 2151P Module
using an RS-485 half-duplex signal.
1.2.2 Velocity The AV Sensor measures average velocity by using ultrasonic
sound waves and the Doppler effect. The Doppler effect states
that the frequency of a sound wave (or other wave) passed from
one body to another is relative to both their motions. As the two
approach each other, the frequency increases; as they move
apart, the frequency decreases.
AV Sensor
Outer Diaphragm
Reference to
Atmosphere
Piezo-resistive
transducer
Silicone
Fluid

2151P Area Velocity Flow System
Section 1 Introduction
1-3
The AV Sensor contains a pair of ultrasonic transducers. One
transducer transmits the ultrasonic sound wave. As the trans-
mitted wave travels through the stream, particles and bubbles
carried by the stream reflect the sound wave back towards the
AV Sensor. The second transducer receives the reflected wave.
Circuits internal to the module compare the frequencies of the
sound waves and extract the difference. An increase or decrease
in the frequency of the reflected wave indicates forward or
reverse flow. The degree of change is proportional to the velocity
of the flow stream.
1.2.3 Flow Rate Using measurements from the AV Sensor, the 2151P can cal-
culate the flow rate. Many different flow rate conversion methods
are supported:
• Area Velocity
•DataPoints
• Manning Formula
• Two-term Polynomial Equations
•Flumes
•Weirs
Often the 2151P is chosen for applications where a primary
device is not available, nor is it practical to install a primary
device. Therefore, area velocity is usually the conversion method
of choice.
The 2151P is capable of calculating and storing any two con-
version methods simultaneously. This feature is useful when it is
necessary to validate a flow conversion method. For example, the
flow rate at a new site programmed for area velocity conversion
can be directly compared to the flow rate calculated using a
Manning formula.
1.2.4 Total Flow The 2151P can calculate and report the total flow. You can set up
the system to monitor net, positive, or negative total flow from
either of the calculated flow rates.
1.2.5 Data Storage
Through Flowlink, you configure which type of data is logged and
the storage rate. For each measurement, the Data Storage Setup
window lets you turn the primary rate off, or select a rate from 15
seconds to once every 24 hours. If the primary rate is turned off,
the 2151P will not store the measurement (unless a secondary
rate is selected). However, the 2151P will still take readings if
that measurement type is necessary for a calculation.
Secondary rates are used to log data at a different rate when a
user-defined condition exists. For example, a secondary rate can
be used to increase the level and velocity data storage rate when
level is greater than or equal to a point of interest. Secondary
rates give you the best resolution of data, but only when it is
needed. Until the condition is met, the module will conserve
Flow
Ultrasonic
Sound Waves
Particles or
Air Bubbles

2151P Area Velocity Flow System
Section 1 Introduction
1-4
power and memory by storing the data at the primary storage
rate. Like the primary rate, you can turn the secondary rate off,
or select a storage rate of 15 seconds to every 24 hours.
Time Resolution The time resolution of each measurement is one second. That is,
readings are taken at the same time as the time stamp, not col-
lected and averaged over a period of time before the stamp.
Rollover Memory Whether the measurements are stored at the primary or sec-
ondary rate, they are stored in a rollover type of memory. When
full, the module overwrites the oldest data with the newest
readings.
1.3 Identifying Module
Components
The various components of the 2151P and sensor are shown in
Figures 1-1 through 1-3. Items referenced in the figures are
described in Tables 1-1 through 1-3.
Figure 1-1 2151P System, Top Left View
1
2
3
Table 1-1 2151P Area Velocity Flow System - Top Left View
Item No.
Fig. 1-1 Name Description
1 Communication Indicator Illuminates when module communications are
active.
2 Serial Number Label Lists the product ID and unit serial numbers,
and defines the hazardous areas for which the
2151P is certified.
3 Desiccant Cartridge and
Hydrophobic Filter
The cartridge holds desiccant that dries the
reference air. The filter prevents moisture from
entering the reference line.

2151P Area Velocity Flow System
Section 1 Introduction
1-5
Figure 1-2 2151P System, Top Right View
3
2
1
5
6
4
Table 1-2 2151P Area Velocity Flow System - Top Right View
Item No.
Fig 1-2 Name Description
1 Communication
Connector
Used to connect to an intrinsically safe communication/barrier cable, which can
then be connected to a 2100 Series module or laptop with Isco Flowlink software.
2 Connector Cap Insert into unused communication connector to terminate the network and protect
it from moisture damage. When the communication connector is in use, the cap
must be stowed in its holder to protect the terminating components inside the cap.
3 Mounting Plate Attaches the module to a flat surface or suspension apparatus.
4 Intrinsically Safe
Power Cable
Used to connect the 2151P to a 12V DC power barrier.
5 AV Sensor Recep-
tacle
Port used to attach the AV Sensor. Insert the protective plug when not in use.
6 AV Sensor Caution
Cautions user to
attach only haz-
ardous area rated
sensors with specific
Isco part numbers.

2151P Area Velocity Flow System
Section 1 Introduction
1-6
Figure 1-3 Components - 2151P Area Velocity Sensor
1.4 Technical
Specifications
The following tables provide technical information about the
2151P Area Velocity Flow System and its related components.
• Table 1-4 lists the technical specifications of the 2151P
system.
• Table 1-5 lists the technical specifications of the Area
Velocity Sensor.
• Figure 1-4 and Table 1-6 list information about the
2151P’s communication connector.
1
5
2
4
3
Table 1-3 Components - 2151P Area Velocity Sensor
Item No.
Fig. 1-3 Name Description
1 Connector Cap Protects the connector. When the connector
is not in use, this cap must be in place to pre-
vent damage to the connector pins and refer-
ence air tubing.
2 Connector Attaches to the AV Sensor receptacle on the
2151P Module.
3 Serial Number Label
Safety Warning
Lists product ID and unit serial numbers.
Read the label for important safety informa-
tion.
4 AV Sensor Body The AV Sensor Body is placed in the flow
stream to measure level and velocity.
5 Cable 25 ft (7.6 m) cable containing the reference
air tubing and conductors to transfer level
data, velocity data, and AV Sensor power. (A
75 ft (22.8 m) cable is available.)

2151P Area Velocity Flow System
Section 1 Introduction
1-7
Table 1-4 Specifications – 2151P Area Velocity Flow System Module
Size (HWD) 3.75 9.5 11.0 inches 9.5 24.0 28.0 cm
Weight 6.0 lbs (2.5 kg)
Material High-impact molded polystyrene
Enclosure Rating NEMA 4X, 6P IP 68
Power 12V DC, 100 mA nominal (CSA approved intrinsically safe)
Program Memory Non-volatile, programmable flash; can be updated using PC without opening enclo-
sure; retains user program after updating
Flow Rate Conversions Up to 2 independent level-to-area and/or level-to-flow rate conversions
Level-to-Area Conversions
Channel Shapes Round, U-shaped, rectangular, trapezoidal, elliptical, with silt correction
Data Points Up to 50 level-area points
Level-to-Flow Rate Conversions
Weirs V-notch, rectangular, Cipolletti, Isco Flow Metering Inserts, Thel-Mar
Flumes Parshall, Palmer-Bowlus, Leopold-Lagco, trapezoidal, H, HS, HL
Manning Formula Round, U-shaped, rectangular, trapezoidal
Data Points Up to 50 level-flow rate points
Equation 2-term polynomial
Total Flow Calculations Up to 2 independent, net, positive or negative, based on either flow rate conversion
Data Storage Memory Non-volatile flash; retains stored data during program updates
Capacity 395,000 bytes (up to 79,000 readings, equal to over 270 days of level and velocity
readings at 15 minute intervals, plus total flow and input voltage readings at 24
hour intervals)
Data Types Level, velocity, flow rate 1, flow rate 2, total flow 1, total flow 2, input voltage
Storage Mode Rollover with variable rate data storage based on level, velocity, flow rate 1, flow
rate 2, total flow 1, total flow 2, or input voltage
Storage Interval 15 or 30 seconds; 1, 2, 5, 15, or 30 minutes; or 1, 2, 4, 12, or 24 hours
Bytes per reading 5
Setup and Data Retrieval Serial connection to IBM PC or compatible computer with Isco Flowlink for
Windows Software Version 4.x
Baud Rate 38,400
Operating Temperature 0° to 140°F -18° to 60°C
Storage Temperature -40° to 140°F -40° to 60°C

2151P Area Velocity Flow System
Section 1 Introduction
1-8
Table 1-5 Specifications – Area Velocity Sensor
Materials
Sensor Epoxy, chlorinated polyvinyl chloride (CPVC), stainless steel
Cable Polyvinyl chloride (PVC), chlorinated polyvinyl chloride (CPVC), stainless steel
Size (HWD) 1.9 3.3 15.2 cm 0.75 1.31 6.00 in.
Cable Length 7.6 m 25 ft
23m 75 ft
Cable Diameter 0.9 cm 0.37 in.
Level Measurement
Method Submerged pressure transducer mounted in the flow stream
Transducer Type Differential linear integrated circuit pressure transducer
Range10.010 to 3.05 m 0.033 to 10 ft.
Maximum Allowable Level 10.5 m 34 ft.
Accuracy2±0.003 m ±0.010 ft
Long Term Stability ±0.007 m/yr ±0.023 ft/yr
Operating Temperature Range -10° to 60°C -14° to 140°F
(applies to flow media when the sensor is immersed)
Temperature Compensation 0° to 50°C 32° to 122°F
Velocity Measurement
Method Doppler Ultrasonic
Frequency 500 kHz
Transmission Angle 20° from horizontal
Typical Minimum Depth for
Velocity Measurement
25 mm 1.0 inch
Range -1.5 to +6.1 m/s -5 to +20 ft./s
Accuracy3Velocity Error
-1.5 to +1.5 m/s (-5 to +5 ft./s) ±0.03 m/s (±0.1 ft./s)
1.5 to 6.1 m/s (5 to 20 ft./s) ±2% of reading
Operating Temperature -40° to 60°C -40° to 140°F
Operating Atmospheric Pressure 80 to 110 kPa (0.8 to 1.1 bar)
Temperature Measurement
Accuracy ± 2°C
NOTES:
1. Actual vertical distance between the area velocity sensor and the liquid surface
2. Maximum non-linearity , hysteresis, and temperature error from actual liquid level
3. In water with a uniform velocity profile and a speed of sound of 1480 m/s (4850 ft./s)
4. The serial tag of the sensor contains important X marking, indicating special safety conditions that must be
observed.