An experiment to get the accuracy of strain gages

Strain gauges are usually based on a metallic foil pattern. The gauge is attached to the test piece with a special adhesive. As the test piece is deformed, so the adhesive deforms equally and thus the strain gauge deforms at the same rate and amount as the test piece.

First, thank you for your genuine interest in this! I'm going to answer the question as best I can, seeing I don't have all the info. Does this imply you can't insert anything into the flow? 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.

So in a way, it doesn't quite matter. That is Is it flexible enough to distort sufficiently to measure with a strain gauge? It -should- be flexible enough to be measured with a strain gauge, but so far I haven't managed to find one that is thin yet flexible, at least not flexible enough for a small gauge to measure it.

That being said, it is flexible enough to easily bend by hand, I don't know if that is enough for it to be detected by the gauge. One idea I had was to put the gauge inside the tube, to be affected by the flow, but that would probably cause short circuit problems.

If they can't be glued could a suitable collar be fashioned? Hmm, the tube I have in mind is plastic of sorts. I have yet to try to glue a strain gauge to it. Do you want absolute pressure or just variations?

What sort of speed and frequency of measurement is required? As fast as a human's blood pressure could change, so anywhere between 60mmHG and mmHG. As for the speed and frequency, it will depend on how fast the pressure could change. So every heart beat, so. I've been doing my research on the strain gauges and already found a strain gauge that is resistant to magnetic fields.

I found that a constantan alloy, and consists of two identical grids, with one stacked directly above and insulated from, the other. That way they cancel out the noise.

Finding it has lead me to this question, as I don't know how to figure out it's measuring accuracy. Either degrees or degrees, depending if we go with room temperature or that of the human body.

Quite honestly you gave me a lot of questions to think about myself and which I'll be asking the prof I'm working with! So thank you for that! Saw your reply after I posted Aleph!

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.

How to know a strain gauge's accuracy? | Physics Forums

You might be able to use a laser vibrometer LDV to measure the change in shape of the pipe directly to an accuracy of nm, or even pm with special image processing software. They can measure steady-state as well as dynamic effects. Yes unfortunately it has to be quite small.

I've never heard of LDV, so I will do some searching on that and get back to you!The purpose of this experiment is to improve the results obtained in experiment 1 by the previous measurement method by using a Wheatstone bridge (Figure 2) that comprises of four nominally identical strain gauges.

Nov 16,  · The calculations allow you to design a gage installation to get a predetermined sensitivity and accuracy, but do not take into account certain practical realities, such as the exact effect of nearby stress concentrations.

Telling you what you need to know about noise & vibration

The earliest strain gages were mechanical devices that measured strain by measuring the change in length and comparing it to the original length of the object. For example, the extension meter (extensiometer) uses a series of levers to amplify strain to a readable value.

Accuracy: Strain measurement Our case studies are available to view for registered users, Imetrum customers and sales partners. Please login or register to access these resources. 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.

What Is A Strain Gauge?

Observe the sensitivity to temperature changes using. A full-bridge strain gage configuration has four active strain gages and is available in three different types.

Types 1 and 2 measure bending strain and type 3 measures axial strain. Only types 2 and 3 compensate for the Poisson effect, but all three types minimize the effects of temperature.