BDI ST350 User manual

ST350 - STRAIN
TRANSDUCER

Version 3.0, 0718
OPERATIONS MANUAL: ST350 STRAIN TRANSDUCER
3
Document Revision History
Version
Date
Changes
1.0
5/15/2012
Initial release document
2.0
6/7/2012
Updated to reflect the change in hardware
Document formatting updated
2.1
1/2/2013
Interim version-minor changes to formatting
2.2
4/2/2013
Updated to reflect the recent CE compliance approval
Power ratings updated
3.0
7/20/18
Updated to include new corrosion protection
Minor changes to specifications
New template and styles were applied
No part of this operations manual may be reproduced, by any means, without the written consent of BDI.
The information contained within this manual is believed to be accurate and reliable. However, BDI assumes no responsibility
for errors, omissions or misinterpretations. The information herein is subject to change without notification.
Copyright © 1989 –2018
Bridge Diagnostics, Inc. (dba BDI)

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WARRANTY INFORMATION
BDI warrants its products to be free from defects in materials and workmanship under normal use and service for thirty-six (36)
months from date of shipment. This warranty shall be void if any products have been subjected to modification, misuse, neglect,
accidents of nature, or shipping damage. Batteries have no warranty.
All equipment manufactured by BDI is intended for use by a qualified professional only. Under this warranty BDI's obligation is
limited to repairing or replacing (at BDI's option) of defective products. In no event shall BDI be liable for punitive, exemplary,
special, indirect, incidental, or consequential damages and the customer shall assume all costs of removing, reinstalling, and
shipping of defective products. EXCEPT AS STATED HEREIN, BDI MAKES NO WARRANTIES, EXPRESSED OR IMPLIED, AND
SPECIFICALLY DISCLAIMS ANY IMPLIED WARRANTY OF FITNESS FOR A PARTICULAR PURPOSE OR MERCHANTABILITY.
Before returning any product, BDI technical support must be contacted at [phone] or by visiting BDITEST.COM/contact
and submitting a request. A technician will help determine the nature of the problem and if it cannot be resolved, authorization
will be given to return the item. A return merchandise authorization (RMA) will be sent to the customer to be filled out and
shipped back with the equipment. BDI will not accept shipment of any product without prior authorization as provided herein.
Ship all equipment to:
BDI
ATTN: TECHNICAL SUPPORT
740 S PIERCE AVE UNIT 15
LOUISVILLE CO 80027
+1.303.494.3230

Version 3.0, 0718
OPERATIONS MANUAL: ST350 STRAIN TRANSDUCER
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TABLE OF CONTENTS
1. Introduction .......................................................................................................................................................7
1.1 About the ST350 Strain Transducer ..................................................................................................................7
1.2 About this manual..........................................................................................................................................7
2. ST350 Overview..................................................................................................................................................8
2.1 Technical Specifications ..................................................................................................................................8
2.2 Options and Accessories .................................................................................................................................9
2.3 Applications ................................................................................................................................................10
3. Operation.........................................................................................................................................................10
3.1 Theory of Operation.....................................................................................................................................10
3.2 Potential Strain Measurement Issues ..............................................................................................................11
3.2.1 Temperature Variation..........................................................................................................................11
3.2.2 Instrumentation Cable Issues ................................................................................................................ 12
3.3 Connecting to Data Acquisition Systems ..........................................................................................................12
3.3.1 Excitation Voltage ................................................................................................................................12
3.3.2 Electrical Connections...........................................................................................................................12
3.3.3 Applying Calibration Factors ..................................................................................................................13
3.4 Verifying ST350 Output ................................................................................................................................13
3.4.1 Resistance Test ...................................................................................................................................13
3.4.2 Resolution/Noise Test...........................................................................................................................14
3.4.3 Sensor Response Test ..........................................................................................................................14
3.4.4 Field Adjusting Excessive Offsets............................................................................................................ 15
3.5 Verifying Accuracy .......................................................................................................................................15
3.5.1 Factory Calibration ...............................................................................................................................15
3.5.2 Items for Consideration for User Verification Tests.................................................................................... 15
4. Installation....................................................................................................................................................... 17
4.1 General Installation Guide ............................................................................................................................. 17
4.1.1 Prepare Mounting Area .........................................................................................................................17
4.1.2 Installation..........................................................................................................................................18
4.2 Installation on Steel Members........................................................................................................................19
4.1 Installation on Concrete Members .................................................................................................................. 23
4.1.1 Concrete Mounting Studs ...................................................................................................................... 23
4.1.2 Attaching ST350 with Extension to R/C Members ......................................................................................24
4.1.3 Attaching Extension to the ST350...........................................................................................................25
4.2 Installation on Other Surfaces........................................................................................................................29
4.2.1 Timber Members..................................................................................................................................29
4.2.2 Composite Materials .............................................................................................................................29
5. Maintenance & Recalibration...............................................................................................................................29
5.1 Maintenance Considerations ..........................................................................................................................29
5.2 Recalibration...............................................................................................................................................29

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LIST OF TABLES
Table 1: ST350 Specifications ................................................................................................................................... 8
Table 2: ST350 Options and Accessories .................................................................................................................... 9
Table 3: Typical Applications for ST350 strain transducers ...........................................................................................10
Table 4: ST350 Wiring Designations & Intelliducer Pinout ............................................................................................12
Table 5: ST350 Extension Limits...............................................................................................................................24
Table 6: Gage Extension Factors ..............................................................................................................................24
Table 7: Maximum Strain Ranges .............................................................................................................................25
LIST OF FIGURES
Figure 1: ST350 Drawing (inches) ............................................................................................................................. 8
Figure 2: ST350 Schematic......................................................................................................................................11
Figure 3: Noise levels of the ST350 on a 24-bit data acquisition system .........................................................................14
Figure 4: Typical Smooth Output Response and Zero Offset .........................................................................................14
Figure 5: Alignment Marking for ST350 Installation .....................................................................................................18
Figure 6: Mounting Position & Surface Preparation Marks.............................................................................................18
Figure 7: Typical ST350 Installation..........................................................................................................................19
Figure 8: Identifying Metric vs. Imperial Tabs.............................................................................................................19
Figure 9: Mounting Tabs on the ST350 using the Tab Jig.............................................................................................20
Figure 10: Marking ST350 Center Mounting Location...................................................................................................20
Figure 11: Tab Removal Tool (TRT) ..........................................................................................................................21
Figure 12: TRT with a Tab Inserted ..........................................................................................................................22
Figure 13: Removing a Tab with the TRT...................................................................................................................22
Figure 14: ST350 Concrete Drilling Jig.......................................................................................................................23
Figure 15: ST350 Extension Mounting Jig ..................................................................................................................26
Figure 16: ST350 Extension Mounting Diagram ..........................................................................................................26
Figure 17: Aligning ST350 and Extension in the Jig .....................................................................................................27
Figure 18: Extension Alignment Tab .........................................................................................................................27
Figure 19: Attaching Tab to Extension.......................................................................................................................27
Figure 20: ST350 With Extensions Attached to an R/C Structure ...................................................................................28

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OPERATIONS MANUAL: ST350 STRAIN TRANSDUCER
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1. INTRODUCTION
1.1 ABOUT THE ST350 STRAIN TRANSDUCER
The ST350 strain transducers have been designed for recording dynamic and other induced strains on all types of structural
members and to be compatible with most data acquisition systems. While mostly used in rugged field applications, they are also
suitable for many laboratory and manufacturing scenarios. The ST350 internal circuitry consists of a full Wheatstone Bridge with
four fully-active 350Ω foil gages optimized to provide a high electrical output for a given strain magnitude. Each transducer is
individually calibrated with a highly-accurate, N.I.S.T.-traceable calibration system.
Each unit is fully sealed, designed to exceed the IP67 rating, and equipped with two pre-drilled mounting holes to keep the gage
lengths consistent for all installations. Based on the structure’s material and length of time the ST350 is to be installed, various
mounting techniques can be used including adhesives, welding, expandable anchors, and screws.
1.2 ABOUT THIS MANUAL
This is a comprehensive document that explains the functions and features of the ST350. BDI also manufactures two types of
data acquisition systems, which will be referenced throughout the manual.
1. Structural Testing System (STS): Rugged, wireless, battery powered DAQ that includes an intelligent (Intelliducer)
connector design, which makes the system extremely easy to deploy on a variety of field projects.
2. Structural Monitoring System (SMS): Modular system with 4- or 16-channel nodes that can be used in laboratories or
on permanent large scales monitoring projects.
The following highlighted message blocks will periodically appear and contain important information that the user should be
aware of.
STOP: This symbol and corresponding message represents information regarding the device that if not
followed could lead to damaging the device! Pay close attention to this message.
WARNING: This symbol and corresponding message represents vital information and is critical for the
device operation and/or the operational settings/configuration.
INFORMATION: This symbol and corresponding message represents general information and/or tips on
successfully operating/configuring the device.

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2. ST350 OVERVIEW
2.1 TECHNICAL SPECIFICATIONS
Figure 1: ST350 Drawing (inches)
Table 1: ST350 Specifications
MODEL
ST350
TYPE
350Ω
CIRCUIT
Full Wheatstone bridge with 4 active 350Ω strain gages
EXCITATION VOLTAGE
+1.0 to +10.0 Vdc
OUTPUT
mV level, ratiometric to Excitation Voltage
OFFSET
< 1.5 mV at time and temperature of calibration
POWER RATING:
MAX
TYPICAL
INTELLIDUCER1
300 mW
72 mW @ +5.0 Vdc
13 mW @ +5.0 Vdc
STRAIN RANGE
±4,000 µε (Calibrated to ±2,000 µε)
FORCE REQUIRED FOR 1,000µε
~17 lb (~76N)
TYPICAL SENSITIVITY
~500 με/mVout/Vin
ACCURACY2
< ±1%
CALIBRATION
Individually calibrated using N.I.S.T.-traceable automated system.
Calibration curve & factor provided
THERMISTOR (OPTIONAL)
3 kΩ - NTC
EFFECTIVE GAGE LENGTH
3.0 in (76.2 mm) [Gage Extensions available for R/C structures]
CABLE
Custom lead cable length made to order:
IC-02-187 [22 AWG, 2 shielded pair, drain wire, red PVC jacket]
IC-02-250 [22 AWG, 2 shielded pair, drain wire, blue PVC jacket]
IC-03-250 [24 AWG, 3 shielded pair, drain wire, black PVC jacket]
HOUSING
Machined 6061 Aluminum Alloy

Version 3.0, 0718
OPERATIONS MANUAL: ST350 STRAIN TRANSDUCER
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CORROSION PROTECTION
Hard Anodized Clear (MIL-A-8625 Type III)
WEATHER PROTECTION
Designed to exceed IP67
Optional 100 ft (30 m), waterproofing available
TEMPERATURE RATING3
-58° to +176 °F (-50° to +80 °C)
SIZE
4.38 in x 1.25 in x 0.50 in (111 mm x 32 mm x 12.7 mm)
WEIGHT
0.19 lb (85 g)
MOUNTING HOLES
Through holes for ¼ in (M6) bolts or anchors
Reusable mounting tabs (gluing/welding)
1Intelliducer connector required with STS Intelliducer data acquisition nodes.
2Accuracy defined at the calibrated ±2,000 µε range.
3Temperature limit based on instrumentation cable operating temperatures, call BDI for wide temperature range cable options.
2.2 OPTIONS AND ACCESSORIES
The ST350 is supported by several available options and accessories depending on the application and use. See Table 2 for a
list of options and accessories that we supply.
Table 2: ST350 Options and Accessories
OPTIONS AND ACCESSORIES
Intelliducer Connector –Required for use with STS data acquisition nodes,
cable is connected and potted for a weatherproof seal
Integrated Thermistor –Temperature range of -55 °C to +220 °C, ±0.5 °C
accuracy
Reusable Mounting Tabs –¼-20 or M6, zinc plated steel mounting tab
Tab Jig –Machined aluminum jig for safely attaching mounting tabs to the
strain transducer; Includes either 7/16 in or M10 end wrench
Gage Extension –Machined aluminum 24 in (610 mm) gage length extension
with 3.0 in (76 mm) increments

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Extension Jig –Aluminum mounting jig for safely accurately attaching Gage
Extensions
Installation Jigs –Welding or concrete drilling jigs
Protective Covers –Insulated aluminum protective covers
2.3 APPLICATIONS
Table 3: Typical Applications for ST350 strain transducers
HIGHWAY AND RAILWAY BRIDGES
Static and Dynamic Live Load Testing
Moveable Bridge Operation Forces
Overload Detection
RIVER CONTROL STRUCTURES
Navigation Lock Gate Load Responses (Lift, Miter, Radial)
Tainter Gates (Trunnion Friction)
Mechanical Drive Components (Torque, Force)
CABLE FORCES
Individual force & group balancing –static
LABORATORY TESTING
Classroom teaching tool
Measure responses for structural members and components
Integrate with existing A/D systems
BUILDINGS
ASTM Standard Floor Load Tests
Construction Vibration Monitoring
Concrete Curing Temperature Tracking
Earthquake Response Monitoring
3. OPERATION
3.1 THEORY OF OPERATION
The internal components of the ST350 consist of a custom-manufactured 350-Ohm Wheatstone bridge foil transducer-class
strain gage mounted inside a flexible proving ring. The four active arms are arranged inside the ring in such a manner that the
total output provides approximately 3.5 times the output compared to a typical ¼-bridge foil gage under the same induced
strain level.