Embedding Thermoucouples Into Refrigeration Lines

marx290 · 07-29-15, 11:31 PM

I thought I would offer my experience making thermocouple sensors which are sealed directly inside of refrigeration lines. I did this so I could get more accurate or responsive readings, when I'm experimenting. I realize this is not necessarily practical for most applications, but I find it very useful when trying to understand small nuance characteristics of a system, so as to possibly exploit them.

Sealing Thermocouples Into Refrigeration Lines | musings on entropy

A little sample pic:

-Mike

MEMPHIS91 · 07-31-15, 04:50 PM

Very interesting work. Glad you found one that works well. Could you provide a side by side comparison of the thermocouple in and thermocouple on the copper tubing? I would be interested to know the differance.

marx290 · 07-31-15, 11:16 PM

Hey, Memphis91. I'd be happy to experiment with it further, in a few days. I can say from experience, that at higher temperature difference, (colder than ambient, or hotter) that the difference between temps taken inside versus outside, can be as much as 12 degrees F, maybe more. Closer to ambient temperature, the discrepancies are much smaller. Additionally, the response time is better. I'll be very interested to compare the two once I get some live graphing set up.

I'll make a short video next week, demonstrating the value of these devices.

TechShop · 08-08-15, 01:57 PM

I'm always chasing better tools and more data. You've done both here. I like it.

The bubbles are harmless but assuming you have a vacuum pump to evacuate the systems you're working on you could build a small chamber to vacuum de-gas the epoxy.

Perhaps use a few large steel pipe fittings or a small pressure cooker.

Place the potted sensors upright, inside the pressure cooker while the epoxy is liquid and pull a vacuum. Let it stand for 10 or 20 minutes so the bubbles can work their way up and out.

marx290 · 08-08-15, 02:59 PM

Yeah. The father of a friend of mine does epoxy machining, and I guess he does a vacuum chamber to remove the bubbles. I would build one, but I don't have the room for another piece of equipment right now. Perhaps in the future, when I have another need for one. You're right, to date I have not had any problems I can associate with the bubbles.

Once I move into data collection, I might be switching to thermistors, calibrating them all together for more accurate results.

07-29-15, 11:31 PM	#1
marx290 Vapor Compression Goon Join Date: Mar 2013 Location: Portland, OR Posts: 63 Thanks: 11 Thanked 22 Times in 11 Posts	Embedding Thermoucouples Into Refrigeration Lines I thought I would offer my experience making thermocouple sensors which are sealed directly inside of refrigeration lines. I did this so I could get more accurate or responsive readings, when I'm experimenting. I realize this is not necessarily practical for most applications, but I find it very useful when trying to understand small nuance characteristics of a system, so as to possibly exploit them. Sealing Thermocouples Into Refrigeration Lines \| musings on entropy A little sample pic: -Mike Attached Thumbnails __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts. Last edited by Daox; 07-31-15 at 07:18 PM..

07-31-15, 11:16 PM	#3
marx290 Vapor Compression Goon Join Date: Mar 2013 Location: Portland, OR Posts: 63 Thanks: 11 Thanked 22 Times in 11 Posts	Hey, Memphis91. I'd be happy to experiment with it further, in a few days. I can say from experience, that at higher temperature difference, (colder than ambient, or hotter) that the difference between temps taken inside versus outside, can be as much as 12 degrees F, maybe more. Closer to ambient temperature, the discrepancies are much smaller. Additionally, the response time is better. I'll be very interested to compare the two once I get some live graphing set up. I'll make a short video next week, demonstrating the value of these devices. __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

08-08-15, 02:59 PM	#5
marx290 Vapor Compression Goon Join Date: Mar 2013 Location: Portland, OR Posts: 63 Thanks: 11 Thanked 22 Times in 11 Posts	Yeah. The father of a friend of mine does epoxy machining, and I guess he does a vacuum chamber to remove the bubbles. I would build one, but I don't have the room for another piece of equipment right now. Perhaps in the future, when I have another need for one. You're right, to date I have not had any problems I can associate with the bubbles. Once I move into data collection, I might be switching to thermistors, calibrating them all together for more accurate results. __________________ To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.

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07-31-15, 04:50 PM	#2
MEMPHIS91 Journeyman EcoRenovator Join Date: Apr 2015 Location: Oxford, MS USA Posts: 496 Thanks: 69 Thanked 87 Times in 61 Posts	Very interesting work. Glad you found one that works well. Could you provide a side by side comparison of the thermocouple in and thermocouple on the copper tubing? I would be interested to know the differance.

08-08-15, 01:57 PM	#4
TechShop FNG Join Date: Jul 2015 Location: Washington Posts: 71 Thanks: 8 Thanked 19 Times in 13 Posts	I'm always chasing better tools and more data. You've done both here. I like it. The bubbles are harmless but assuming you have a vacuum pump to evacuate the systems you're working on you could build a small chamber to vacuum de-gas the epoxy. Perhaps use a few large steel pipe fittings or a small pressure cooker. Place the potted sensors upright, inside the pressure cooker while the epoxy is liquid and pull a vacuum. Let it stand for 10 or 20 minutes so the bubbles can work their way up and out.