Campbell ST350 Manual de usuario

ST350 Strain Transducer

2/08

Campbell Scientific, Inc.

Warranty and Assistance

The ST350 STRAIN TRANSDUCER is warranted by CAMPBELL

SCIENTIFIC, INC. to be free from defects in materials and workmanship

under normal use and service for thirty-six (36) months from date of shipment

unless specified otherwise. Batteries have no warranty. CAMPBELL

SCIENTIFIC, INC.'s obligation under this warranty is limited to repairing or

replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.

The customer shall assume all costs of removing, reinstalling, and shipping

defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL

SCIENTIFIC, INC. will return such products by surface carrier prepaid. This

warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products

which have been subjected to modification, misuse, neglect, accidents of

nature, or shipping damage. This warranty is in lieu of all other warranties,

expressed or implied, including warranties of merchantability or fitness for a

particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,

indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following

contact information is for US and International customers residing in countries

served by Campbell Scientific, Inc. directly. Affiliate companies handle

repairs for customers within their territories. Please visit

www.campbellsci.com to determine which Campbell Scientific company

serves your country. To obtain a Returned Materials Authorization (RMA),

contact CAMPBELL SCIENTIFIC, INC., phone (435) 753-2342. After an

applications engineer determines the nature of the problem, an RMA number

will be issued. Please write this number clearly on the outside of the shipping

container. CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.

RMA#_____

815 West 1800 North

Logan, Utah 84321-1784

CAMPBELL SCIENTIFIC, INC. does not accept collect calls.

ST350 Table of Contents

PDF viewers note: These page numbers refer to the printed version of this document. Use

the Adobe Acrobat® bookmarks tab for links to specific sections.

1. Introduction ...............................................................1-1

1.1 Typical Application.............................................................................. 1-1

2. Specifications............................................................2-1

3. Sensor Alignment and Installation..........................3-1

3.1 Alignment............................................................................................. 3-1

3.2 Installation............................................................................................ 3-2

3.3 Adjusting Excessive Transducer Offset................................................ 3-3

4. Wiring.........................................................................4-1

4.1 Initial Check-Out.................................................................................. 4-1

4.2 Excitation Voltage................................................................................. 4-1

5. Mounting of Sensor to Various Surfaces................5-1

5.1 General................................................................................................. 5-1

5.2 Mounting Information for Different Types of Surfaces....................... 5-2

5.2.1 Steel............................................................................................ 5-2

5.2.2 Reinforced Concrete................................................................... 5-3

5.2.3 Pre-stressed Concrete.................................................................. 5-6

5.2.4 Timber ........................................................................................ 5-7

6. Calibration and Validation........................................6-1

7. Maintenance, Replacement Parts, and Repairs......7-1

7.1 Maintenance .......................................................................................... 7-1

7.2 Replacement Parts................................................................................ 7-2

8. Datalogger Programming.........................................8-1

8.1 CR1000 Example ................................................................................. 8-1

8.2 CR5000 Example ................................................................................. 8-2

Appendices

A. Special Instructions for using ST350....................A-1

A.1 Instructions for Using ST350 Strain Transducer Extensions on

Reinforced Concrete Structures.............................................................. A-1

A.2 Attaching the Concrete Extension to a Strain Transducer .................. A-2

ST350 Table of Contents

B. ST350 Accuracy Verification..................................B-1

B.1 Verifying the Accuracy of ST350 Strain Transducers......................... B-1

B.1.1 Introduction ............................................................................... B-1

B.1.2 Background................................................................................ B-1

B.1.3 Factory Calibrations................................................................... B-1

B.1.4 Temperature Effects................................................................... B-2

B.1.5 Specimen Type and Size............................................................ B-2

B.1.6 Items for Consideration ............................................................. B-2

B.1.7 Other Considerations................................................................. B-4

C. Calibration Sheets...................................................C-1

C.1 Example of Calibration Sheet — BDI Supplied.................................. C-1

C.2 Example of Calibration Sheet — CSI Supplied................................... C-2

Index.........................................................................Index-1

Figures

3-1. Measurement Axis...............................................................................3-1

3-2. Surface Preparation - Location ............................................................3-2

3-3. ST350 Mounting Example...................................................................3-2

4-1. ST350 Electrical Wiring Diagram.......................................................4-1

7-1. ST350 Strain Transducer Test Output .................................................7-1

7-2. Proper Connection to Data Acquisition System for Tension and

Compression............................................................................................7-2

A-1. Extension Jig...................................................................................... A-3

A-2. Drawing Extension Jig.......................................................................A-3

A-3. Picture Compressing ST350 for Mounting Purposes ........................A-4

A-4. Extension Alignment Tab.................................................................. A-4

A-5. Desired Gage Length .........................................................................A-4

A-6. Example of Ceiling Mounting............................................................A-5

C-1. Bridge Diagnostics Calibration Sheet................................................ C-1

C-2. Campbell Scientific’s Calibration Sheet ............................................ C-2

Tables

A-1. Recommended Lower and Upper Gage Limits................................. A-1

A-2. Maximum Strain Ranges....................................................................A-2

Section 1. Introduction

This manual provides information for interfacing the ST350 Strain Transducer

to Campbell Scientific’s Dataloggers. Unless otherwise specified, all part

numbers are Campbell Scientific's.

This manual contains information on sensor specifications, operating

principles, installation, alignment, and calibration. The multiplier and offset

values given here are based on calibration data obtained from the Bridge

Diagnostic’s Calibration Sheet (see example Appendix C).

The most direct approach to quantifying live-load stresses in a structural

member is to record the induced strain. However, it can be tedious work

installing foil strain gages in the field since careful surface preparation and

soldering is often required. Now, most field strain gage installations can be

replaced with the highly accurate ST350 Strain Transducer. These units are

rugged and can be installed in any weather. Since they are pre-wired and easy

to mount, ST350 Strain Transducers will drastically reduce your field

installation time.

1.1 Typical Application

This transducer is typically used for dynamic or event driven stress in structural

members such as bridges or buildings. The ST350 Strain Transducers have

been designed for recording Live Load strains only. Hence it is assumed that

there will be little to no temperature change during any short time-span testing

sequence.

When a transducer is attached to a structure, it is forced to have the same

deformation as the structure. However, if a temperature increase (or decrease)

occurs, and since the ends of the sensor are "anchored", the transducer will

expand between the end blocks and register compression. The same goes for a

drop in temperature which will register tension. If the sensor is to be mounted

on the structure for a long period of time, it will need to have its "zero" reset

periodically as it drifts around with temperature changes.

1-1

Section 1. Introduction

1-2

Section 2. Specifications

Effective gage

length: 3.0 in (76.2 mm). Extensions available for use on R/C

structures.

Overall Size: 4.375 in x 1.25 in x 0.5 in (111 mm x 32 mm x 13 mm).

Cable Length: 10 ft (3 m) standard, any length available.

Material: Aluminum

Circuit: Full wheatstone bridge with four active 350 Ωfoil

gages, 4-wire hookup.

Accuracy: ±2%, reading individually calibrated to NIST standards.

Strain Range: Approximately ±2000 εμ.

Force req’d for

1000 με: Approximately 17 lbs. (76 N).

Sensitivity: Approximately 500 εμ/mV/V.

Weight: Approximately 3 oz. (85 g).

Environmental: Built-in protective cover, also water resistant.

Temperature

Range: -58°F to 185°F (-50°C to 85°C) operation range.

Cable: BDI RC-187: 22 gage, two individually-shielded pairs

w/drain.

Options: Fully waterproofed, Heavy-duty cable, Special quick-

lock connector (available upon request).

Attachment

Methods: C-clamps, threaded mounting tabs & quick-setting

adhesive, wood screws, or concrete anchors.

2-1

Section 2. Specifications

2-2

Section 3. Sensor Alignment and

Installation

3.1 Alignment

The BDI ST350 will only measure strain in the axis in which it is aligned with,

therefore the more accurate the alignment, the more accurate the measurements

will be. The easiest way to align a transducer is to mark a “grid” type pattern

for both the proper foot placement and measurement axis. First, locate the

center-line of the gaging area in both the longitudinal and transverse directions.

For example, if measurements are to be obtained at the mid-span of a joist,

locate the midpoint between the supports and the center-line of the joist. The

longitudinal mark should be about 8 inches long and the transverse mark about

4 inches long. This will allow the marks to be seen while the transducer is

being positioned. This can be seen in the picture below.

MEASUREMENT

AXIS

FIGURE 3-1. Measurement Axis

From the transverse mark, make two additional marks at 1.5 inches on either

side of the centering mark (see below photo). The areas circled below are the

portions of the cross-section that the necessary surface preparations must be

performed. Surface preparation techniques are explained in Section 5:

Mounting of sensor to various surfaces.

3-1

Section 3. Sensor Alignment and Installation

3”

SURFACE PREP.LOCATIONS

FIGURE 3-2. Surface Preparation - Location

3.2 Installation

Once surface preparation is complete, the transducer can be installed using the

selected mounting technique (see Sections 5- Mounting of Sensors to Various

Surfaces). The two marks 1.5 inches from the center-line are used to locate the

transducer longitudinally; align these marks with the center of the transducer

feet. Notice that the front of the transducer (end opposite of the cable) as been

machined to a slight point. This point, along with the cable exit on the rear of

the transducer, should be aligned with the measurement axis line to ensure that

strain is being measured parallel to the measurement axis. An installed

transducer can be seen in the picture below. Note that if an R/C extension is

used, the longitudinal mark will need to be 30 inches long in order to be seen

behind the transducer/ extension combination. It is important that this line is

drawn carefully as the strains are inherently more susceptible to error due to

misalignment as the gage length increases.

FIGURE 3-3. ST350 Mounting Example

3-2

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