Got this stretch sensor from adafruit , and it was highly unstable.
Measured with both ohm meter and by sending AC thru it to measure the current.

Adafruit states that the resistance will be approximately 350ohm/inch, I got like 300-700ohm/inch.

Can someone recommend me with an accurate stretch sensor?
Would this one be more accurate?

 

You did read the part about its response time being VERY slow..

the rubber will shrink back, although its not very 'fast' and it takes a minute or two to revert to its original length.

Why not describe your application or intended use for this sensor?
I've never seen nor heard of a "stretch" sensor in a real world professional application.
That's a gimmicky toy basically where stability/accuracy/quick response is not required.

There are numerous other ways to measure displacement..

 

I've never seen nor heard of a "stretch" sensor in a real world professional application.
That's a gimmicky toy basically where stability/accuracy/quick response is not required.

+1
You'll never see a "stretch sensor" used in industry.

Tell us what you're doing and we can find a reliable way to do it.

 

Depending on several factors, I can see it used for a cheap, disposable, around-the-chest respiration transducer. Offsets and gain could be automatic in the electronics.

Ken

 

You did read the part about its response time being VERY slow..



Why not describe your application or intended use for this sensor?
I've never seen nor heard of a "stretch" sensor in a real world professional application.
That's a gimmicky toy basically where stability/accuracy/quick response is not required.

There are numerous other ways to measure displacement..

Yeah I know it has a decay time, but the thing is when I stretch it to lets say from 1inch to 2inch and holds it still I get different values each times, and the value is not stabilized even after 30minutes.
Here are the values after 30 minutes, before each try the rubber is shrunken back to it initial value(320-380omh)
First try : 988ohm
Second try:1200ohm
Third try:775ohm
Fourth try:680ohm
Fifth try: 1044ohm

 

+1
You'll never see a "stretch sensor" used in industry.

Tell us what you're doing and we can find a reliable way to do it.

Stage 1.
I want to measure the length variations of "something", that "something" can curve and expand in any directions.
Wish to measure down to millimetre.


Stage 2.
In realtime the data is sent to TI USB-6008 and then Labview for graph processing.


Stage 2 is completed, problem is inaccuracy in stage 1, can't even calibrate that thing.

 

Yeah I know it has a decay time, but the thing is when I stretch it to lets say from 1inch to 2inch ....

when interested in precision, consider products that have datasheet. that way you get precision, repeatability etc specified properly instead of "about"...

and then ensure you are always within limits. for example going from 1 to 2 inch is 100% stretch while link states that you should not exceed 60%. the product is likely already damaged and out of spec, whatever that was.

you can use wire draw encoder for example

 

Stage 1.
I want to measure the length variations of "something", that "something" can curve and expand in any directions.
Wish to measure down to millimetre.

It sounds like you're trying to measure flubber.
Are being intentionally vague? I won't play the 100 questions game. If you want help you need give a reasonable description, and a picture is worth 1000 words.

 

Would this one be more accurate?

Given that they think that stretching something that is 6" to a length of 12" is a 50% elongation, I wouldn't put a lot of stock in their specs or their expertise.

 

It sounds like you're trying to measure flubber.
Are being intentionally vague? I won't play the 100 questions game. If you want help you need give a reasonable description, and a picture is worth 1000 words.

Sorry for this mysteriousness.
But I've signed a confidentiality agreement, so I can not give out the exact object to be measured and the whole procedure.

The nearest thing I can compare to is a balloon, when it is filled with air the surface will expand in all directions.
Or temperature dependent tape that is taped to something curved, as the temperature changes, it will increases or decreases.

 

What about a string pot?
What sort of accuracy/precision do you require?
What is the measurement delta?
Must you measure distance? Maybe pressure (for your balloon example)
stain gauge maybe?

Sounds like an interesting problem but if you've signed an NDA then I'm afraid the necessary information cannot be exchanged properly here and all we would be doing is taking random guesses to solve a virtually unknown problem to us.

But I'd make a guess that a string pot would work for this if a junk "stretch sensor" was attempted. Its MUCH more precise.
Good luck...

 

Sorry for this mysteriousness.
But I've signed a confidentiality agreement, so I can not give out the exact object to be measured and the whole procedure.

The nearest thing I can compare to is a balloon, when it is filled with air the surface will expand in all directions.
Or temperature dependent tape that is taped to something curved, as the temperature changes, it will increases or decreases.

sorry for the lack of tact. Its just that we get an overwhelming amount of posters around here who are just too lazy to provide enough information to help them, and it gets irritating after a while.

so I guess I will entertain the 100 question game.

is this object circular? are you trying to measure circumference?