Thermocouple gauge

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
David Nagy
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Thermocouple gauge

Post by David Nagy » Wed Jan 22, 2014 3:35 am

I found this gauge (http://www.pchemlabs.com/product.asp?pid=4118) and I thought it might work for a fusor and I had a few questions about it. Firstly is it worth getting (I found this too http://www.ebay.com/itm/Hastings-DV-4D- ... 4ceff81e21). Second if I go with the conflat one what is the included baffle for?

Ps don't say I should have looked at the faqs, because I did.
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Re: Thermocouple gauge

Post by JakeJHecla » Wed Jan 22, 2014 3:39 am

Please read the forum archives. There is plenty of good info on thermocouple gauges. Others have used similar units, and they seem to work sufficiently. As for the baffle, I would imagine it's there to keep out diffusion pump oil and other debris.

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Re: Thermocouple gauge

Post by Carl Willis » Wed Jan 22, 2014 6:32 am

For best price and function in a TC gauge, go with a brand-new Hastings DV-6M or equivalent (e.g. 6000 series from LDS or Lesker). The Varian 531 is also popular and inexpensive, but has inferior sensitivity in the micron range. The gauge tubes are $40-50 new with the typical 1/8" NPT fitting. Used tubes or new old stock tubes are sometimes available on eBay, but often these are defective or dirty. The controllers can be found all the time on eBay at affordable prices in the range of $50. Buying a used controller is typically a safe investment.

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Richard Hull
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Re: Thermocouple gauge

Post by Richard Hull » Wed Jan 22, 2014 4:54 pm

Carl's advice is specific and great. however, a scan of the vacuum forum FAQs might have yielded.

viewtopic.php?f=25&t=3592

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Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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Re: Thermocouple gauge

Post by David Nagy » Wed Jan 22, 2014 9:46 pm

The conflat one in the original post has a 5 pin connector and I noticed that it is much more difficult to find this type of connector than the 9 pin type. Is the 4 pin connector varian-Agilent specific and if not could I use one of their gauges with a different make of controller?
In some sort of crude sense, which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose.

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Re: Thermocouple gauge

Post by Carl Willis » Wed Jan 22, 2014 9:59 pm

A TC gauge tube must be used with a controller designed for that specific type. Using a mismatched controller with a tube will result in incorrect readings at best, and possibly a damaged tube. Luckily, the common types mentioned earlier are very popular, and on any given day, eBay will have multiple offerings listed. If a controller is sold without the keyed octal socket these two tube types (and most others) use, no need to get bent out of shape about that; it's a $2 part.

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Re: Thermocouple gauge

Post by David Nagy » Wed Jan 22, 2014 10:57 pm

So basically I could use this tube with any other brand of controller as long as the connector is the same?
In some sort of crude sense, which no vulgarity, no humor, no overstatement can quite extinguish, the physicists have known sin; and this is a knowledge which they cannot lose.

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Re: Thermocouple gauge

Post by AllenWallace » Thu Jan 23, 2014 4:18 am

No you cannot use difference gauge controllers unless they are specifically matched to the tube type. See http://www.belljar.net/tcgauge.htm . All the tubes referenced in the article have the same octal connector, but have very different electrical specifications.

FYI, you can use a variable power supply, a current limiting resistor, DVM and an excel spread sheet graph to make an effective gauge controller.

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Re: Thermocouple gauge

Post by Carl Willis » Thu Jan 23, 2014 6:15 am

A DV-6M tube (or off-brand equivalent from Lesker, Duniway, LDS, etc.) will work only with the Hastings controller made specifically FOR THAT TUBE (or off-brand equivalent). Same applies to the Varian 531. The gauge faces say what tube they will work with on the front. If a controller is offered up with no identifying information, you will have to look at close-up photos and do a little bit of Googling to see if it is compatible with the tube you want to use. Definitely start by picking a tube. If this was my choice, I would go for a DV-6M brand-new and be done with it. Then wait for deals, make offers, or outright buy a compatible controller.

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Richard Hull
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Re: Thermocouple gauge

Post by Richard Hull » Thu Jan 23, 2014 7:05 pm

Again, as noted above, the following FAQ explains this point.

viewtopic.php?f=25&t=3592

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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