# An experiment to get the accuracy of strain gages

It is not practically possible to stretch and extend a piece of copper wire by these amounts. It is necessary to know the relationship between resistance and voltage.

As can be seen in Figure 5 it is actually a five wire configuration. Any change in resistance in any arm of the bridge results in a nonzero output voltage. Technical Learning Home W hen external forces are applied to a stationary object, stress and strain are the result.

When a load is applied to the surface, the resulting change in surface length is communicated to the resistor and the corresponding strain is measured in terms of the electrical resistance of the foil wire, which varies linearly with strain.

Strain Gage Designs Optical sensors are sensitive and accurate, but are delicate and not very popular in industrial applications. Therefore, the strain experienced by the test specimen is transferred directly to the strain gage, which responds with a linear change in electrical resistance.

Back to Top 3. The gage is produced by first depositing an electrical insulation typically a ceramic onto the stressed metal surface, and then depositing the strain gage onto this insulation layer.

That is, the volt per strain is known. Do you want absolute pressure or just variations? The reason for this requirement is that strain gauges are often on long wires and all wires have their own resistance. The variations in the electrical resistance of the grid are measured as an indication of strain.

Sensor Designs The deformation of an object can be measured by mechanical, optical, acoustical, pneumatic, and electrical means. Diffused semiconductors often are used as sensing elements in pressure transducers. First, thank you for your genuine interest in this!

True loop of initial bridge balance. For example, the resistance of a copper wire which has a resistivity of 1. Resistors R2, R3 and R4 are known resistances. The grid pattern maximizes the amount of metallic wire or foil subject to strain in the parallel direction.

Strain gauge readings can be affected by variations in the temperature of the strain gauge or test piece. Only the strain in the desired direction, across Rx, in the test piece affects the measured voltage readings.

Whatever is used to measure the strain gauges resistance will itself have its own resistance. Figure 7 shows one possible mode to balance the bridge.

Do you want absolute pressure or just variations? For example, the extension meter extensiometer uses a series of levers to amplify strain to a readable value.

That will produce a very small strain unless you have a flexible pipe, but a flexible pipe could give calibration problems by not staying circular i. The semiconductor bonded strain gage is a wafer with the resistance element diffused into a substrate of silicon. Bonded resistance strain gages can be used to measure both static and dynamic strain.

Gage lengths from 0. Another advantage is that the stressed force detector can be a metallic diaphragm or beam with a deposited layer of ceramic insulation.

Their limitations include sensitivity to ambient temperature variations, which can be compensated for in intelligent transmitter designs.

The electrical resistance of metallic grid changes in proportion to the amount of strain experienced by the test specimen. G when "Balanced Completed" turns on, turn off the bridge balance option. Each requires a different strain gage arrangement. The four different types of strain are axial, bending, shear, and torsional.

This type of loop required that all tasks within Stack Zero be performed then those tasks in Stack One, etc. Seeing as this is a preliminary study done by us students we are going to be using water as a liquid, but the long term goal of the project is using a liquid that has the same viscosity as blood.

Silicon wafers are also more elastic than metallic ones.

So every heart beat, so.Feb 09,  · Hello all. I am looking over various strain gauges as I need to purchase one for my project. However, I have never worked with them before, and I cannot seem to figure out how to know its accuracy (able to detect a certain change in pressure, for example changes of the scale of 1mmHg), seeing as none of the datasheets seem to have that kind of data.

coatings, and electrical resistance strain gages. In this experiment the strain gage will be utilized. There are three steps in obtaining experimental strain measurements using a strain gage: 1. Selecting a strain gage 2. Mounting the gage on the test structure and 3. Measuring strains corresponding to specific loads.

Laboratory experiment 1. Strain gages.

This experiment can be divided in a number of tasks: 1. Apply strain gages. 2. Connect the gages to an amplifier. Balance an d calibrate by determine th e overall sensitivity by connecting a known resistance across one of the gages. 3. Observe the sensitivity to temperature changes using.

During this laboratory experiment, the strain in a loaded cantilever beam will be measured in both the axial and transverse directions using strain gages and a Wheatstone Bridge Circuit. From the measured strain the strain gauge measure the tension and compression strain on the beam.

The strain measurement results obtained with the proposed method and those obtained with an electrical-resistance strain gauge were found to be in good agreement.

It describes the absolute physical limits for the resolution of strain gage transducer signals and how carrier frequency technique can get very close to the boundary of .

An experiment to get the accuracy of strain gages
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