Frequently asked questions
External force applied to an elastic material generates stress, which subsequently generates deformation of the material. At this time, the length L of the material extends to L+ΔL if applied force is a tensile force. The ratio of ΔL to L, that is ΔL/L, is called strain. (Precisely, this is called normal strain or longitudinal strain.) On the other hand, if compressive force is applied, the length L is reduced to L- ΔL. Strain at this time is (- ΔL)/L. Strain is usually represented as ε . Supposing the cross sectional area of the material to be A and the applied force to be P, stress σ will be P/A, since a stress is a force working on a definite cross sectional area. In a simple uniaxial stress field as illustrated below, strain ε is proportional to stress σ, thus an equation σ = E × ε is satisfied, provided that the stress σ does not exceed the elastic limit of the material. “E” in the equation is the elastic modulus (Young’s modulus) of the material.
ε = ΔL/L
ε : Strain
L : Original length
ΔL : Change due to force P
Because a strain is a ratio between length of two parts, it is a quantity having no dimension. Usually it is represented in a unit of 1×10-6, since the ratio of deformation is often very small. For example, supposing L to be 100mm and ΔL to be 0.1mm, strain ε is indicated as 1000×10-6strain, because “0.1mm/100mm=0.001=1×10-3=1000×10-6“. To indicate comparatively large strain, “% strain” is also used. In this case, 1% strain equals to 10000×10-6strain.
STRAIN GAUGE CONFIGURATION
A strain gauge is constructed by bonding a fine electric resistance wire or photographically etched metallic resistance foil to an electrical insulation base using an appropriate bonding materials and attaching gauge leads.
SELECTING STRAIN GAUGES
Strain gauges are provided with many convenient features, but they also have limitations. Each strain gauge has its limitations in terms of temperature, fatigue, the amount of strain, and the measurement environment. These limitations must be examined before a strain gauge is used.
- Strain Gauge Features
- Simple construction with a small mass and volume so as not to interfere with the stresses on the specimen.
- Short distance between measuring points for localized evaluation.
- Good frequency response for tracking rapid fluctuations in stress.
- Simultaneous measurement of multiple points and remote measurement.
- Electrical output for easy data processing.
A typical bridge configuration to cancel axial load in bending measurement is shown in “Half bridge with 2-active gauges eliminating tensile strain” in the web page. Here, the strain gauge R1 is mounted on the front side the strain gauge R2 is mounted on the back side. These two strain gauges are connected in half bridge. In this configuration, when full bridge is used, each two strain gauges are mounted on the front side and the back side. If we suppose the front gauges R1 and R2 and the back gauges R3 and R4, these strain gauges are connected in a Wheatstone bridge clockwise R1, R3, R2, R4 (not R1, R2, R3, R4). A typical bridge configuration to cancel bending in axial load measurement is shown in the upper figure of “Full bridge” in the web page. (The lower figure of Full bridge is for torque measurement.) Here, the strain gauge R1 and R3 are in axial direction and the strain gauge R2and R4 are in circumferential direction.
If you have any questions, please be kind to let us know. We would recommend to use two two-element strain gauges like FCM-2.8-350.
Note: When a full bridge is configured on a plate or cylinder, we think it better to bond each one two-element strain gauges on oposite sides of the specimen. Visit Transducer Gauges
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Yes off course we do, please write us your detailed application and what you intend to measure, we can design /suggest from small digital remote location logger to wireless GPS based logger solutions.
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Well it depends on many factors, if the product is really outdated , then reselling it won’t be the best option, but other wise we can have a factory inspection and then decide on buying back or not. Yes, yes it has to be in working condition for sure but also we have to check other factors.
Yes off course, the best way to suggest such a solution would be study the datasheet of your “xyz” datalogger. Else please specify what kind of Analog Inputs your datalogger can accept and what is the Full scale range of your dataloggers Analog Input Channel and what kind of our sensor you are interested in. We can work a optimized solution for you in both case.
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