(-Planning Exercise - Strain gauge Coursework Help -)

In summary, Jack is lost and has been stuck on coursework for several days. He is looking for help and has asked on multiple occasions but has not received a response. He has failed to provide a full transcript of the question and is only providing a summary of the content.
  • #71
how do you attach the weight to the strain gauge and connect it to the circuit at the same time? is there a paritcular way to plug wires in a strain gauge? please answer quickly! :frown:
 
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  • #72
hiya I am doing this exp too. I think ur meant to use some kind of epoxy adhesive. But first u apply some of it to the metal ruler, then stick down a piece of felt for insulation.Then add another layer of epoxy adhesive and stick down the strain gauge. Correct me if I'm wrong people!
 
  • #73
firstkings said:
the experiment is in two parts...

stretch a piece of wire . Add a mass, measure the resistance of the strain gauge. No wheatstone bridge, no crane. Glue (superglue) the strain gauge to the wire. keep adding masses (weights), keep measuring V and I. etc
Is what you mentioned both parts of the experiment?
 
  • #74
Is there anyone who still has tim left?? I've got a lot of tips for u:-
precautions-safety goggles,in case something snaps
use a low voltage
make sure the metal rod doesn't slip
repeat reading to get an average
air the room to prevent temperature from rising too much
 
  • #75
Hey i am doing this experiment as well and have got to hand it in for wednesday has any1 got any idea of then range of the meters we need to use? or the dimensions of a strain gauge and the material on which u mount it? This is all sssssssssooooooooooooo confusing?
 
  • #76
firstkings said:
the experiment is in two parts...

stretch a piece of wire . Add a mass, measure the resistance of the strain gauge. No wheatstone bridge, no crane. Glue (superglue) the strain gauge to the wire. keep adding masses (weights), keep measuring V and I. etc

never use super glue! it will melt the strain gauge... that the whole point of superglue... to melt the two substances together...it will damage the gauge...trust me.....dont use superglue
 
  • #77
use a ruler clamped on a clamp stand.... masses atttached to the ruler...move the masses along bout 10cm and take a reading... again move 10 cm...another reading...repeat experiment...draw say u going to draw table and graph.....hey presto...u done it...caio
 
  • #78
any 1 who carez

The material seems to be at the candidates discretion, and as to the dimensions, i hav read that is only small being about 16mm long but don't quote me on that....mine also has to be in on wednesday (i go to Joeseph Ruston college in Lincoln and got an extension to the time :smile: )
i think that i will use a standard metre rule of beech wood, and mount the stress gauge with adhesive suggested earlier in this topic called cyanoacrylate, mounted at the highest stress point, this should give sufficeint strain on the gauge for decent results, i will use a 10g weight set with a hook-base attached via string through a hole in the end of the rule to apply the strain. also i will suggest saying that ur using the quarter brige wheat-stone bridge circuit with a variable resistor for adjustment and a stress gauge in the circuit for the measurement of the resistance(obvious reasons apply...lol).
Also the crain in the introduction to the question has no relevance to question.
Please if anyone has suggestions for improvement can than post them please?
 
  • #79
hi i have until wed 19th as well, I have no clue wat a strain gauge is either!- Alot of use i am to u ey! do u no wat the dimensions r meant to be? Is that meant to be the metal ruler? the strain gauge has to be as wide as the ruler rite?
 
  • #80
my teacher said it has to be a metal ruler instead of a beachwood one. Is that rite?
 
  • #81
i would have thought that using any kind of ruler would be less effective cos they'd have a large cross sectional area compared to something like metal foil. Considering that it doesn't state the material you need to use, and your only measuring the extension of the strain gauge applying less force, ie less weights would be easier to manage therefore a material with a low young's modilus (is that right? i can't spell) should extend more that a material with a higher young's modilus with the same force applied. the same is true with the cross sectional area.

You'd then also be able to talk about the safety aspecs of the foil/wire snapping rather than working your arse off thinking up something totally irelivant.


on a side note, our actual practical is on wednesday and neither of my physics teachers have 'made' a hassle about buying in strain gauges yet the practical will have something to do with the planning so maybe that's where the crane comes in? i don't know but it might be.

one last thing. does anyone know if we Have to use a wheatstone bridge or will it only icrease the accuracy? is it possible to measure the resistance just by measuring the voltage and the ampage?
 
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  • #82
as i said its at the candidates discretion, I'm already changing my plan I'm changing to a aluminium strip about 20mm x 150mm and i will attach the waits from the bottom with a drilled hole about 10mm from the bottom of the strip i will hange the strip vertically aso it dangles, and attack the gauge about mid way (the gauge doesn't have to be the same width i don't think...)
 
  • #83
devil_uk said:
a drilled hole about 10mm from the bottom

if you drill a hole then all the force will be applied on a small length of the strip. what you need to do instead is use a clip or something along the whole of the bottom of the strip so that the force is applied evenly over it. All this is just scroundging for that extra mark or two though.
 
  • #84
seems like aluminium is the best to use then! Yes I'm going to talk about using a wheatstoe bridge. It isn't nessecary according to other people measuring the voltage and current, But I'm talking about it just for the sake of getting an extra mark or 2. I have looked on many websites, but I can't seem to find one which shows how the gauge is connected into a wheatstone bridge circuit. Or maybe its jus me being thick and not being able to understand it! :confused:
A wheatstone bridge circuit is more accurate to use coz a) it measures really precisely b) shows that the voltage which shows up to force applied. A full wheatstone bridge is always best to use for these reasons. The other ones like half, quarter etc seem to have more disadvantages for some reason, which I can't remember which helps of course!
 
  • #85
according to my teacher, the actual practical has nothing to do with our planning exercise, strain gauges or cranes even!but has got somthing to do with stress and strain.
Anyone who has done theirs give us a hint will ya! pleeze!
 
  • #86
If you attach the gauge to a ruler and then add masses to the end of the ruler how do you work out the forces on the strain gauge??
 
  • #87
http://www.allaboutcircuits.com/vol_1/chpt_9/7.html
http://www.entran.com/gages.htm

the first of these two i found very useful, it shows how the gauge is connected but you've still got to realize that if the amage is kept constant like it is for this experiment (because your not changing the power supply) then the voltage will vary with the resistance, it also shows the full, half and quarter wheatstone bridge.

the second website is an actual strain gauge; we were all talking about them but most of use were ignorant, this page won't help most, me included but i does show that they come in packs of 4 so are designed with a full wheatstone bridge in mind, they also show that the GF is not 2 but 140 or 155 unless i can't read it properly which is very interesting seeing as we were going on about them being only 2 or so, the resistance it shows so is useful but beyond that i can't work anything what any thing means.

can't think of any questions but can't think of anything to write either so something must be wrong...ah well

ah yep; i find the starts the hardest, how are you/how have you started writing you plan cos i can't seem to manage that.
 
  • #88
this is a question for you morph; in the full-bridge, where are all of the strain
gauges attached to and WHY is this more sensitive than, say a quarter-bridge?doesthe full bridge only test for bending rather than streching because otherwise all of the strain gauges will read the same resistance and so the bridge will always stay balenced. this is just my reasoning so tell me if I'm wrong.
 
  • #89
does any1 know how or where to connect the ohmeter and voltmeter on the strain gauge?
 
  • #90
isn't it just in a circuit, so the volt metre would be parallel
 
  • #91
The Actual Practical Is On Moment And Electrolysis..actually This Site Helped Me Alot..i Just Started Mne Today...
Thanx To You All
 
  • #92
i don't undertand the two experiments...i used a metre rule and attached the strain gauge at the centre of the metre rule with the aid of a super glue..and attached a load under the gauge..i don't know whether it is right..we are told to use copper not aluminum as it gives much strain..im now asking..where do we fix the copper..do we put it round the gauge or what...
secondly,do we have to put down two drawings: that of the meter rule and also the second expt...i was told by ma teacher to use a voltmeter if using a wheatstone bridge is going to be complicated.If youve done this sort of expt let me know or youve got better idea..im stuck i need to submit it on wednesday
 
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  • #93
At least I'm not the only one up at this time doing the work... has anyone here finished and handed it in already?
 
  • #94
So far,it seems you guys are making a mistake :surprise: . In the planning sheet it says to investigate how the resistance of a strain gauge depends on the *tensile force*
Tensile forece is:-A stretching force (tension) pulling at both ends of a component or structure along its length.

so basically ,you have to stretch the metal strip or whatever it is you are using, not bend it like in the crane .The crane was just given as an illustration of a forec but they specified what kind of force to look out for:-tensile force. So just to tell u guys not to bend ur metal strip cos it won't be giving u a tensile fore. here's a bit of my diagram tho.

And a strain gauge is a tiny thing, as small as a post stamp so u can just stick it on your surface.
 

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  • #95
If you bend a strip of material, you are still applying a tensile force along its top edge. If you hang a material like in ibnwando's diagram, you will have to use a lot of force to be able to get an appreciable change in length, and therefore resistance. Bending will be much easier in a labotary situation.
 
  • #96
longhairedbean said:
http://www.allaboutcircuits.com/vol_1/chpt_9/7.html

Well I read that the full wheatstone bridge is more sensitive on the exact same website that u mentioned. Its stated towards the end. As for how it is connected, i can't draw it 4 u at the moment my paint is ****ed :mad: so I can't draw at all which helps but I'll try & describe it to u. I am only using one strain gauge and 4 resistors. Set it up in a full bridge circuit except replace the gauges with resitors so u get r1,r2,r3,r4 and there will also be a volt meter in the middle to pick up slight changes in electrical resistance and a voltage supply. If one of the resistors experience anything, this results in an unbalance and something comes up on the voltmeter.
This probably sounds confusing :confused: but I was never good at explaining!
 
  • #97
hmmmmmmmm

thespacedevil said:
never use super glue! it will melt the strain gauge... that the whole point of superglue... to melt the two substances together...it will damage the gauge...trust me.....dont use superglue
:frown: are you sure that will happen, as my physic's teacher hinted at using superglue :confused:, - if this is the case techniqually, would we loose marks in planning to use this as it is really just a theoretical experiment (as it were) as we arent really carrying it out... :confused: :confused: :confused: :confused: oh well i will keep it as it is for now and ask my teacher tomorow
 
  • #98
ibnwando's right, that's exactly how I've set out mine, and apparently that's rite, all i need to know is where i can get more info on what to attach the strain gauge to the metal strip wiv, and what are the safety precautions, if someone wud like 2 help me wiv these 2, i will be glad to email my full plan to that specific person.
 
  • #99
superglue shud be fine as it shouldn't actually get hot anyway. I thought of using epoxy adhesive but I think that it is not ok to use as it has give and is flexible. Safety precautions: safety goggles, nothing on floor to trip over, no water near electricity, use low current as less harmful but still be careful
 
  • #100
i think that some of u r making it more complicated than necessary. You don't need to worry about wheatstone bridges, a voltmeter and an ammeter will be fine and calculate the resistance from V=IR.
 
  • #101
My physics teacher has just sed that epoxy adhesive is good as it is strong but also has give which is good for this experiment! (I'm at a boardig school so my physics teacher is still here!)
 
  • #102
Hey guys,
What did u all put down for your dimensions?
This is the only thing I am stuck on now.
 
  • #103
what ranges of forces are u using?
 
  • #104
range of forces

As they obviously haven't stated, I'm sayin use anywhere between 1-10 N as anything bigger than this could result in whiplash- v dangerous!
what r u sayin about the dimensions?
 
  • #105
Can't be more then 0.1mm as strain gauge will snap
 
<h2>1. What is a strain gauge?</h2><p>A strain gauge is a type of sensor used to measure the strain or deformation of an object. It works by converting the physical force applied to the object into an electrical signal, which can then be measured and analyzed.</p><h2>2. How does a strain gauge work?</h2><p>A strain gauge typically consists of a thin wire or foil that is attached to the surface of the object being measured. As the object is deformed, the wire or foil stretches or compresses, causing a change in its electrical resistance. This change in resistance can be measured and converted into a strain value.</p><h2>3. What are the applications of strain gauges?</h2><p>Strain gauges have a wide range of applications in various industries, including aerospace, automotive, civil engineering, and biomechanics. They are commonly used to measure the strain and stress on structures, machinery, and materials, as well as in the development of new products and materials.</p><h2>4. How accurate are strain gauge measurements?</h2><p>The accuracy of strain gauge measurements depends on various factors, such as the quality of the gauge, the type of installation, and the calibration process. Generally, strain gauges can provide accurate measurements with an error margin of less than 1%.</p><h2>5. What is the process of calibrating a strain gauge?</h2><p>Calibrating a strain gauge involves applying known amounts of force or strain to the object being measured and recording the corresponding electrical signals from the gauge. These signals are then compared to a calibration curve or equation to determine the relationship between the force or strain and the gauge's output.</p>

1. What is a strain gauge?

A strain gauge is a type of sensor used to measure the strain or deformation of an object. It works by converting the physical force applied to the object into an electrical signal, which can then be measured and analyzed.

2. How does a strain gauge work?

A strain gauge typically consists of a thin wire or foil that is attached to the surface of the object being measured. As the object is deformed, the wire or foil stretches or compresses, causing a change in its electrical resistance. This change in resistance can be measured and converted into a strain value.

3. What are the applications of strain gauges?

Strain gauges have a wide range of applications in various industries, including aerospace, automotive, civil engineering, and biomechanics. They are commonly used to measure the strain and stress on structures, machinery, and materials, as well as in the development of new products and materials.

4. How accurate are strain gauge measurements?

The accuracy of strain gauge measurements depends on various factors, such as the quality of the gauge, the type of installation, and the calibration process. Generally, strain gauges can provide accurate measurements with an error margin of less than 1%.

5. What is the process of calibrating a strain gauge?

Calibrating a strain gauge involves applying known amounts of force or strain to the object being measured and recording the corresponding electrical signals from the gauge. These signals are then compared to a calibration curve or equation to determine the relationship between the force or strain and the gauge's output.

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