(im)possible temperature measurement - Any ideas?

[TConnolly]

Due to the Seebeck effect, T/Cs generate their voltage over the entire length of the TC wire. You may find that losses aren't going to be an issue.

If the cable is copper and you use a type T TC then you can use one of the cable conductors and add a constantan conductor. You could actually make several TCs all sharing a single copper common.

Copper ------------+----------------+----

                  /                /

Constantan-------/                /

                                 /

Constantan----------------------/

 

[Andybr]

We use a company in the UK called TC (www.tcdirect.co.uk) who will make you up custom thermocouples or RTDs at very reasonable prices and short lead times. If they do not have a presence in the US then I would think that there are similar suppliers (Omega?). I would think your application should be fairly straightforward provided you can manage feeding the cable into the tube.

Sorry. - Just noticed how old this post is.

 

[leitmotif]

I am curious regarding the outcome of this project.

Dan Bentler

 

[danw]

Me, too.

 

[Lancie1]

I am curious regarding the outcome of this project.

As many have said to me, "yeah, but check the date, it is an OLD thread". As if that makes it any less useful.

I always think about how the world has changed. At one time, knowing what happened in the past was called "studying history" and was considered a valid method to determine actions for the future. Not anymore, as many who see a thread older than 2 weeks start hollering about how the posts are just too old even to read.

 

[rdrast]

As many have said to me, "yeah, but check the date, it is an OLD thread". As if that makes it any less useful.

I always think about how the world has changed. At one time, knowing what happened in the past was called "studying history" and was considered a valid method to determine actions for the future. Not anymore, as many who see a thread older than 2 weeks start hollering about how the posts are just too old even to read.

Since my favorite spammer seems to be targeting old threads for a joke, but the question was asked, there has been no solution to this as of yet. This project is currently on the back burner, as it is more of a curiosity then necessary.

Manufacturing Engineering would love a solution, but we have been unable to come up with anything practical.

 

[Lancie1]

Rd,

I would pick your #1 solution:

Possible solutions I've thought of:
1) Bury a TC in the core, and run a LOT of extension wire - concerned about losses in the fine gauge wire, and the difficulty of the physical hookup.

I have seen #14 Type J TC extension wire. That reduces the voltage drop enough that you should not have any problems reading the signal. Probably #16 TC wire would be plenty large enough. The extra large diameter will also help to prevent wire breakage, because it seems that these TC wires will get a lot of bending as the cable is pulled through the steam tube. Bury 2 or 3 TCs in the cable, and pick the 2 out of 3 that are closest to agreeing, to make sure you have a good temperature signal.

You could use a cable reel to unwind the TC wire as the cable is pulled through. There are TC commutators that allow connecting TC wire across a moving or rotating joint.

 

[glenncovington]

Would it be possible to make a small datalogger the dia. of the cable, battery powered and send it through as a link between cable ends. You could capture the data at what ever rate your memory capacity would hold and then download after it ran through.

Here is an example. Just and idea right?

 

[DamianInRochester]

What is the diameter of the cable and what is the diameter of the tube it runs in? What kind of speeds are we looking at?

 

[Lancie1]

Would it be possible to make a small datalogger the dia. of the cable, battery powered and send it through as a link between cable ends.

My impression is that the goal is to measure the temperature changes in the center of the cable as it moves through the steam tube. So the data logger would need to be buried inside the cable in such a manner that it does not affect the temperature that the cable would see if the data logger was not present. I could be wrong, though.