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Table of Contents
Summary of Contents for BDI ST350
- Page 1 ST350 - STRAIN TRANSDUCER...
- Page 3 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.
- Page 4 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.
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Page 5: Table Of Contents
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 .......................... - Page 6 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 &...
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Page 7: Introduction
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. -
Page 8: St350 Overview
2. ST350 O VERVIEW 2.1 T ECHNICAL PECIFICATIONS 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 <... -
Page 9: Options And Accessories
Temperature limit based on instrumentation cable operating temperatures, call BDI for wide temperature range cable options. 2.2 O PTIONS AND CCESSORIES 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. -
Page 10: Applications
HEORY OF PERATION 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... -
Page 11: Potential Strain Measurement Issues
However, since the transducer ends are anchored to the structural member and the “temperature inertia” of the ST350 is much less, (heats up and cools much faster than the large member) the gage will attempt to expand between the anchored end blocks, which creates a compression (opposite of expected). -
Page 12: Instrumentation Cable Issues
If the ST350 is exposed to direct sunlight during live-load tests, such as on truss members or on top of a concrete slab, significant temperature drift can be experienced during short periods of time due to changing cloud cover and/or breezes. -
Page 13: Applying Calibration Factors
ST350 O ERIFYING UTPUT It is important to periodically verify the integrity and output of each ST350. Below is a list of tests that we recommend to help verify that the ST350 is working correctly: 3.4.1 Resistance Test Using a multimeter, read the Wheatstone Bridge opposing node resistances (black and red leads and then the green and white leads). -
Page 14: Resolution/Noise Test
3.4.3 Sensor Response Test This test is to ensure the ST350 is producing a smooth output and is returning to its original position. Also ensures that the responses correspond to typical structural testing (positive for tension and negative for compression). Run a test at a sample frequency higher than 30 Hz and apply a smooth tension force (gently pulling on each end) followed by a smooth compression force (gently pushing each end). -
Page 15: Field Adjusting Excessive Offsets
If it is determined that zeroing the Wheatstone bridge circuit cannot be accomplished with the DAQs circuitry, then it is possible that the ST350 has either been deformed to a point where it is providing too much offset. Note that the sensor is in compliance if offset is within ±2.5 mV. - Page 16 In almost every case we have seen, a specimen that is supposedly undergoing tension only is actually bending as well. A popular test is to use a "dog bone" with the ST350 mounted on one side and then the whole assembly put into tension. It is almost impossible to get pure tension in this setup since the specimen may be slightly bent to begin with and "straightens out"...
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Page 17: Installation
UIDE The ST350 can be installed on many structure types and in all types of applications, so it is impossible to outline all the details for each installation. However, with practice and experience, the user can select from a combination of the mounting techniques that BDI has developed over the years depending on the application. -
Page 18: Installation
4.3). The two marks 1.5 in (38.1 mm) from the center-line are used to locate the ST350 longitudinally; align these marks with the center of the ST350 feet. Notice that the front of the ST350 (end opposite of the cable) has been machined to a slight point. -
Page 19: Installation On Steel Members
EMBERS In most situations, the most efficient method of mounting an ST350 is using the tab/glue method as it is the least invasive and is truly a “non-destructive testing” technique. The following section outlines an installation for a steel surface. -
Page 20: Figure 9: Mounting Tabs On The St350 Using The Tab Jig
WARNING: Be careful not to over tighten the nuts on the tabs, over tightening may result in bending the ST350. If the ST350 has been bent out of alignment, please send the ST350 back to BDI for realignment and recalibration. -
Page 21: Figure 11: Tab Removal Tool (Trt)
Use the cutout in the TRT or an end wrench; remove the nuts from the tabs. Carefully slide the ST350 from the tabs. Version 3.0, 0718... -
Page 22: Figure 12: Trt With A Tab Inserted
Thread the TRT on to the tab until the face is flush with the foot of the tab as seen below. If a gap remains between the TRT and the tab foot, there is a high likelihood that the stud will be bent in the next step. Also, do not over tighten the tab into the TRT or it will be hard to remove the tab from the TRT. -
Page 23: Installation On Concrete Members
-20 x 1.5 in Power Fasteners Power-Stud or similar and lightly tap in with a hammer to set. Slide on the short side of the ST350 drilling jig on to the stud and tighten the jig in-place and make sure it is properly... -
Page 24: Attaching St350 With Extension To R/C Members
Example of adjusting the output to account for Gage Extension use: This example is using a ST350 with an 18 in extension. All data was collected using the calculated calibration factor and the output is in engineering units. The applied multiplier is calculated as follows, see... -
Page 25: Attaching Extension To The St350
Another item to consider is the available strain range of the ST350. As the gage length is progressively increased, the force on the ST350 imposed by the extension is increased as well for a given amount of strain. This has the effect of reducing the available strain range for the ST350 with extension assembly. -
Page 26: Figure 15: St350 Extension Mounting Jig
Figure 15: ST350 Extension Mounting Jig There is a machined hole in the non-cabled end of the ST350 that will capture a standard ¼-20 (or M6) hex head bolt (see Figure 16). -
Page 27: Figure 17: Aligning St350 And Extension In The Jig
ST350 STRAIN TRANSDUCER OPERATIONS MANUAL: PRESS EXTENSION GENTLY TOWARDS ST350 TO SEAT THE EXTENSION PROPERLY against the ST350 Figure 17: Aligning ST350 and Extension in the Jig STANDARD TAB EXTENSION ALIGNMENT Figure 18: Extension Alignment Tab DESIRED GAGE LENGTH Figure 19: Attaching Tab to Extension... -
Page 28: Figure 20: St350 With Extensions Attached To An R/C Structure
“twist off” at the glue line, particularly if the concrete is slightly rough or not cleaned off properly. Do not attempt to remove the extension from the ST350 while the assembly is still mounted to the structure. Back off the securing nut between the ST350 and extension by holding the extension only. -
Page 29: Installation On Other Surfaces
4.2.1 Timber Members If the ST350 is to be mounted to a timber member or other relatively soft materials, use a 1.5 in self-tapping screw and a power screwdriver. If the wood has any sort of glue laminated section or it has been chemically treated, it is recommended that a pilot hole be drilled. - Page 30 740 S PIERCE AVE UNIT 15 P +1.303.494.3230 LOUISVILLE CO 80027 F +1.303.494.5027 BDITEST.COM sales@bditest.com...
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