RTD Temp probe wire - cat5/6?

[mofox1]

I've got some Auber RTD temp probes with the standard 6' cables which are slightly too short for my preferred set up (otherwise would be very close to my HLT which poses personal injury risk, and unnecessary steam/electrics proximity).

What's a good option for replacing these? From the auber website, they are teflon coated, 7 strand, 24 AWG (0.2mm^2) copper wires.

The current plan is to unwind some CAT5/6 get 3 even lengths and twist back together... thoughts/warnings/recommendations?

 

[QldKev]

I would just use the cat cable without removing the extra wires. The best thing about the 3 wire RTD is it auto compensates for changes in resistance due to cable length changes, just keep all the 3 wires the same length.

 

[mofox1]

That would be the easiest way... Usually not so good at doing that!

My only issue with the above is the aesthetics, the whole cable is rather bulky. I've got some sleeving for the wires, so I'm not worried about having thin little wires catching on stuff.

Still, cheers.

 

[vr4king]

Any copper cable will do as thats the whole reason behind 3/4 wire RTD's is that the cable resistance doesnt really affect the RTD output but in saying that I wouldnt go much over a few meters if we are going longer that that we use a temp transmitter which changes the ressitance to a 4-20mA output that gets scaled back to degC

 

[TheWiggman]

You're safe changing lengths (to a degree as vr4king said) with RTDs. Thermocouples on the other hand are different and the cables have to be of a specific metal.

If you're worried about the appearance why not reach deep and fork out $23 or so on some cable, with leftovers?

 

[mofox1]

Any copper cable will do as thats the whole reason behind 3/4 wire RTD's is that the cable resistance doesnt really affect the RTD output but in saying that I wouldnt go much over a few meters if we are going longer that that we use a temp transmitter which changes the ressitance to a 4-20mA output that gets scaled back to degC

Thanks vr4king - you got industry experience there? I was planning on doing 3m cables - I like the idea of a wireless brewery, but would hate to try and put it into practice :lol:.

Wondering if you know whether there is any point in twisting the wires together as they do for cat5 cable? I wouldn't think RF interference would matter much for this, but assuming I use individual wires, I figured it couldn't hurt (even if it's just to keep them together under whatever sleeving I use).

You're safe changing lengths (to a degree as vr4king said) with RTDs. Thermocouples on the other hand are different and the cables have to be of a specific metal.

If you're worried about the appearance why not reach deep and fork out $23 or so on some cable, with leftovers?

Thanks Wiggman, just been to Jaycar. That alarm cable looks good and feels very sturdy. Didn't end up getting it though, because the wires were slightly thinner than the 24 AWG used in the auber ones (0.14mm^2 vs 0.2mm^2). Not sure how much that matters, but figured I should stick to the same or thicker conductor than previously used.

Bought some cat5 to cut up as the wires in that are 24 AWG... will play with that and see if it's going to work out otherwise I'll give the alarm cable a go (also sold per meter @ 80c - so all of $7.20 for 9m).

If all works out, I'll have enough slack space to mount the control panel on a extending/swivel TV bracket - cool. B)

 

[Ditchnbeer]

I lengthened my RTD cable by using good quality & shielded alarm cable. I covered each internal wire connection with heatshrink and then covered he whole join with a larger size heatshrink and all good, looks neat, safe from spills and works a treat!

 

[vr4king]

Hey mofox1 yes I do have industry experiance.....My job is an instrumentation technician so I work alot with RTD's T/C's etc and spend a lot of time designing and calibrating temp measuring systems. Three meters should be good if its good copper wire
Wireless is certianly possible we built a system for hydro testing pipelines that are hundreds of kilometers long using RTD's to temp transmitters and then using radio to send data back to a laptop that data logs pressure and temp over periods of up to 3 days..........Perks of my job is I get to nail all brewing temps with good quality gear....But I still manage to hash my mash temp due to heat loss while mashing in grrrrr.

RTD's are hard to beat for most applications......with good quality joins you cant go wrong

Oh and dont worry about RF interefence the reason wires are twisted is to minimise the magnectic field effect that is produced when current is passed through a conductor with current flowing in opposite directions through the wire being twisted it cancels out any field to some extend........A resistance measuring device shouldnt have any/minimal current passing through it to have any effect at all...