How to Measure length of a steel tube with or without PLC

gandhi

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Join Date
Aug 2010
Location
*******,Tamil Nadu
Posts
14
Hi,

We want to measure the legth of a hollow steel tube which will be moving in a conveyor.

The length of the tube may vary from 2 to 6 meters

Is there any easy way to do this kind of measurement.

Kindly suggest your ideas.

Thanks for all your help..
 
A sensor and an encoder?

A sensor detects the tube and then start counting encoder pulses. You'll need to do a bit of maths to work out the relationship between encoder pulses and distance but it should work.

How accurate does it need to be ?
 
gandhi said:
Hi,
We want to measure the legth of a hollow steel tube which will be moving in a conveyor.
The length of the tube may vary from 2 to 6 meters
Is there any easy way to do this kind of measurement.
Kindly suggest your ideas.
Thanks for all your help..
Click to expand...
Do you need to measure exact length? Or just verify that it is within certain range?
In both cases, what actions will be taken based on the result?
 
Vison camera is well capable I use cognex 5100 measures down to .1mm you have to make a calibration setup to convert pixels to real world units. You can mount the camera almost anywhere and transform the image to allow for perspective distortion.
 
easiest guarenteed way of measuring the tube to with in 0.5mm

Stop the conveyor
get out a tape measure
connect it to one end
read the value on the other end.

Now Post the details as to what you actually need please
Along with the information of what you are doing
 
Lasers

The LD-6001 Laser Length Measurement System
can take accurate measurements with accuracy to one thousands of an inch
in motion

however if you know conveyor speed, use a photo eye. When eye is blocked start a timer created from the PLC's system
milisecond timer function, when the photo eye clears, stop the timer and convert to ft/sec = distance traveled = length
reset timer.
 
Last edited:
Photoswitch and encoder on conveyor. Photoswitch wires to interrupt input(don't wait for PLC scan). When photoswitch switches on record the encoder position. When it switches off record the encoder position again. Now compute the difference between the two encoder readings and convert encoder counts to distance.
 
you could use an 'inch worm' to crawl the length of the pipe

Guy's you are missing the OP's Question

How long is a piece of string

This OP is asking you to design this for him
It is his job - let him specify what he wants
- the title - with or without PLC makes this un answerable.
We all know many methods
so what does the OP want??????
 
Last edited:
asterof said:
The LD-6001 Laser Length Measurement System
can take accurate measurements with accuracy to one thousands of an inch
in motion

however if you know conveyor speed, use a photo eye. When eye is blocked start a timer created from the PLC's system
milisecond timer function, when the photo eye clears, stop the timer and convert to ft/sec = distance traveled = length
reset timer.
Click to expand...

This would only work if the conveyor is an accurate fixed speed. I personally think encoders are much more reliable. In my humble... 🍻
 
iant said:
so what does the OP want??????
Click to expand...

I think the OP has said what he wants in his original post...

gandhi said:
Hi,

We want to measure the legth of a hollow steel tube which will be moving in a conveyor.

The length of the tube may vary from 2 to 6 meters

Is there any easy way to do this kind of measurement.

Kindly suggest your ideas.

Thanks for all your help..
Click to expand...

Seems straight forward to me. Now we just need a bit more information and some feedback on the suggestions that have been made already.

;-)
 
Most common I have seen and easiest to work is a encoder wheel setup.

The encoder rides the pipe as it passes by.

That said how accurate the measurement needs to be plays a factor in how to measure. How fast the conveyor is moving is a factor. Also the location of the pipe on the conveyor, as in is the pipe in the same postion relative to the center of the conveyor.
 

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