HBM offers a range of strain gauges comprising an extensive assortment for widely differing applications from experimental stress analysis to durability testing through transducer manufacturing.
Furthermore, HBM offers all the needed components and accessories for installing the strain gauge. The strain gauges are classified as follows.
Strain Gauges for Durability Testing and Experimental Stress Analysis
The different kinds are:
- Linear strain gauges – These record strain in the direction of alignment of their measuring grids. An application is determining the modulus of elasticity on compression and tension bars.
- Double strain gauges – These are used in cases where two linear measuring grids need to be laid parallel to each other for instance to record the bending load of a bending beam. Four active strain gauges are used normally in the Wheatstone bridge circuit.
- T rosettes – These have two measuring grids arranged on a carrier perpendicular to each other. They are normally used in experimental strain analysis to determine the biaxial stress state with known principle directions and to construct transducers with a design corresponding to a tension/compression bar.
- V-shaped strain gauges – these products also have two measuring grids arranged perpendicular to each other. They are also referred to informally as “shear strain gages.” They are used to construct torque transducers, also called shear force transducers.
- Rosettes with 3 measuring grids – available in two basic shapes identified by the angular spacing of their measuring grids. The two designs are 0°/45°/90° rosettes and 0°/60°/120° rosettes. They are used to determine the biaxial stress state with unknown principle directions based on magnitude and direction.
- Full bridge strain gauges – equipped with four measurement grids that are switched to a Wheatstone full bridge. They have several applications such as determining shear load on shearing columns or to determine a torsion moment of a shaft if it is only accessible on one side for SG installation.
- Membrane rosettes – These devices are used for the construction of membrane pressure transducers. Positive strain proportions and negative ones of equal magnitude are added together within the Wheatstone bridge circuit.
- Strain gauge chains – combine a number of evenly spaced grids that share the same carrier. Typical designs of SG chains are measuring grid direction parallel or perpendicular to the longitudinal chain axis, measuring grid direction alternating between parallel and perpendicular to the longitudinal chain axis, and SG rosette chain. Strain gauge chains are used for determining the stress curve over a specific section or the shift in the peak value due to the impact of loading being introduced at a moving point.
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Figure 1. Strain gauges for durability testing and experimental analysis. Image credit: Hottinger Baldwin Messtechnik GmbH
Strain Gauges for Transducer Manufacturers
HBM offers strain gages that are available with various creep compensation values designed particularly for transducer manufacturing (figure 2).
These include the following types:
- Linear strain gauges
- Double linear strain gauges
- Single shear strain gauges
- Double shear strain gauges
- Columnar strain gauges
- T rosettes
- Half-bridge strain gauges
- Full-bridge strain gauges
- Membrane rosettes
- Nickel resistors
- Strain gage accessories.
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Figure 2. Strain gauges for transducer manufacture. Image credit: Hottinger Baldwin Messtechnik GmbH
Optical Strain Gauges
Optical strain gauges (figure 3) are based on Fiber Bragg Gratings. One can benefit from the numerous advantages of measuring with light. HBM offers the following optical strain gauges:
- K-OL - Optical strain gage based on fiber Bragg gratings
- K-OR - Optical rosette: Small and rugged
- K-OTC - Optical temperature compensation sensor
- OptiMet – for fiber-optic sensors.
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Figure 3. Optical strain gauges. Image credit: Hottinger Baldwin Messtechnik GmbH
Adhesives and Bonding Material for Strain Gauges
HBM offers bonding material to attach the strain gauge to the test object (figure 4). The features of the adhesives and bonding material include:
- Transfer of test object deformation to the strain gauge with minimal loss
- Stable behavior across the most possible temperature and strain range as possible
- The strain gauges and the test object are not affected.
The different types offered by HBM are:
- EP150, epoxy resin adhesive for strain gages - can be used with all types of strain gages
- EP310S, two-component epoxy resin adhesive, enabling extremely thin adhesive layers, is sprayable
- X120, visco-elastic two-component adhesive for installing optical fibers
- X280, cold-curing two-component epoxy resin adhesive - can be processed at minimum cost and effort
- X60, fast curing adhesive - very easy dosage and application
- Z70, single component cold curing adhesive made of cyanacrylate.
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Figure 4. Adhesives and bonding materials. Image credit: Hottinger Baldwin Messtechnik GmbH
Protective Coating for Strain Gauges
Strain gauges are protected against external impacts (figure 5) such as mechanical damage or humidity as even small fluctuations in the atmospheric humidity affect the measured signal of an open gage. HBM offers a broad range of suitable means for gage protection.
The different kinds of protective coating offered by HBM are:
- ABM75 - Aluminum foil c/w kneading compound
- AK22 - Viscous putty
- NG150 - Nitrile rubber
- PU140 - Covering agent - single component solvent-based polyurethane lacquer
- SG250 - Transparent silicon rubber
- SL450 - Transparent silicone resin
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Figure 5. Protective coating. Image credit: Hottinger Baldwin Messtechnik GmbH
Accessories for Installing Strain Gauges
HBM offers cleaning agents, aids for bonding, solder terminals, and much more, practically all that is needed for a good strain gauge application is available. The accessories (see figure 6) offered are:
- Cleaning pads - Cellulose for cleaning of strain gages and strain gage application surfaces
- DAK1 - Strain gage starter kit
- DAK2 - Strain gage installation case
- FS01 - Flux pen
- Lead-free resin cored solder - For strain gage applications
- Polyimide tape
- Resin cored solder as used in strain gage applications.
- RMS1 - Cleaning solvent
- RMS1-SPRAY – The spray cleans quickly for rapid strain gage installation
- RSP120 - Cleaning agent dispenser
- Solder Terminals - LS2, LS212, LS224, LS7/5/4
- Teflon foil
- Wires & stranded wires - Paint insulated copper wire, PVC ribbon cable, Jumper wire, Flexible wire, Very flexible wire.
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Figure 6. Strain gauge accessories from HBM. Image credit: Hottinger Baldwin Messtechnik GmbH
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This information has been sourced, reviewed and adapted from materials provided by HBM, Inc.
For more information on this source, please visit HBM, Inc.