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Need advice: SE027 (PTFE) vs SE030 (Fibreglass)

Which product is right for your exact requirements

Need advice: SE027 (PTFE) vs SE030 (Fibreglass)

Postby Julian » Fri Nov 14, 2008 7:11 pm

I need to measure air temperatures at various places in a computer cabinet. All sensors will be in free air and the temperatures will range from 20C up to possibly 70C although I doubt I'll realistically see much above 55C. I plan to use a TC-08.

My confusion is which thermocouples to buy. I know I want type K and I need a 2m lead but that still leaves me one choice, PTFE or fibreglass insulation for the wires. What are the pros and cons of these two and, for my application, which is the most appropriate choice?

- Julian
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Postby Julian » Thu Nov 20, 2008 6:59 pm

Hmm. Is this board monitored? It seems to me like a pre-sales advice forum would be one that should be looked at quite closely by Pico Technology staff. The only thing that has stopped me from placing an order for 1 x TC-08 + 8 sensors this week is that I don't know which sensors to order. This is also a test purchase and at least one additional TC-08 plus sensors is in the budget and we may end up adding a third to that as well.

Let me try to amplify and explain to you why I'm so clueless.

Here's what I know about PTFE. Last month my plumber did a temporary fix in my bathroom using thick black PTFE tape. It smelled like a freshly laid motorway, i.e. it stank like new tarmac, and was designed to stay very, very tacky for months after application. Surely the PTFE on the SE027 isn't like this? Then again, maybe it is designed to be moisture resistant (drawing on my knowledge that plumbers use it) which is a feature I don't need. So, is it tacky to the touch? What benefits and drawbacks do PTFE bring?

Here's what I know about fibreglass. They build canoes with it! This makes me worry that maybe the SE030 will have very rigid leads and be difficult for me to route the sensors into the tighter spots in the test chassis that I need to monitor. Then again, does fibreglass give better thermal insulation to the sensor cables? I might need to route the cables through hotter areas than the temperature I am measuring so I want to minimise any heat in the cables being transferred by thermal conduction to the sensor and distorting the reading. Is there any issue with this and do PTFE and fibreglass differ in their properties on this?

If someone could just tell me the relative pros and cons of the PTFE vs fibreglass coating then I could place my initial order. Also, are the cable outer diameters similar for both? I know this all sounds trivial but if we're likely to end up spending a couple of hundred quid on sensors then we might as well make the optimum choice.

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Postby ziko » Wed Dec 03, 2008 9:58 am

Hi Juan sorry for the late response, I was consulting an expert. Here is what he said:

"PTFE (Fluoroplastic Insulation) is normally specified in applications where one or more of the following properties are required:
1. Resistance to high temp up to 250 C.
2. Low temperature flexibility down to -75 C.
3. Resistance to acid & chemical attack.
4. Resistance to solvents.
5. Thin wall insulation for reduced space and weight.
6. Non infallibility.
7. Very low water resistance and absorption.

Fibreglass insulation mainly used for higher temperatures in non immersion applications due to the fact that it is highly absorbent as it is a weave rather than a extrusion as with plastics.
Temperature rating upto 700C for some high temp fibreglass's. Standard insulation temperature 350C. It is not recommended for low temperatures as it looses flexibility below 0C.
It is fairly flexible in normal applications but does not provide good mechanical protection due to its construction.
"
Hope this helps.
Ziko

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