Fusion Message Board

In this space, visitors are invited to post any comments, questions, or skeptical observations about Philo T. Farnsworth's contributions to the field of Nuclear Fusion research.

Subject: Re: Thermocouple Meters/Data Mining
Date: Dec 13, 9:01 am
Poster: Richard Hull

On Dec 13, 9:01 am, Richard Hull wrote:

>In a couple of posts, Richard Hull sings the praises of the DV-6M or the KJL-1518 thermocouple gauge tubes vs the Varian 531, due to the increased resolution at the lower end of the scale. I own a couple of Varian 801-type gauges, which use the 531 tube. Below 10 mircons, they resolve to 1 micron, although the scale is a bit pushed together. How much better is the low end resolution of the gauges using the DV-6M(is the meter scale more spread out)?

The 1518 is without a doubt, the best tube on the market and one of the cheapest. The scale is so expanded that midscale on the proper 10mv meter is 50 microns!!! Check you 531 meter and see what mid scale is! 2nd tremendous advantage is the normal fil current is only about 10 ma and I have a complete 1518 meter system whihc is totally portable in a tiny 2" deep by 4X5 box and it use a single 1.5 volt "D" cell and has been in use for two years on the one battery.

I originally bought the Duniway 531 digital readout gauge and it can be seen in the fusor video. It is a fine gauge, but the low end is still kind of shakey. I now use only analog gauge readouts for thermocouple gauges. I reserve the digital readouts for my capacitive manometers.

Finally, if you have a duniway catalog, they used to have a photo of both of their analog metered gauges. one with the DV-6M and the other the 531 check out the meter faces for yourself. The 1518 is just a trifle more expanded at the low end than the DV-6M. RH


>On another note, folks new to the list can learn a lot by going through the previous postings here. I went digging last night for the thermocouple tubes mentioned above, as well as Richard Hull's post on using an AC 44XLS spark plug for a high voltage vacuum feed through.
>Another wonderful reference (thanks, Mr. Hull) is the Kurt J. Lesker catalog (the founder passed away recently, R.I.P.). I'm putting together a baratron vacuum gauging system, and the Lesker catalog had information on my baratron components unavailable at the manufacturer's site. A tip of the hat... A lot of the information available in the catalog is also present on their web site. Other good catalogs to have around are the ones from Duniway, Varian, MDC, and Nor-Cal. All have useful infomation, though not as many fundamental nuggets as the Lesker catalog. The Matheson web site(mathesongas.com)is a good reference for gas handling and regulators.


Thanks for re-iterating a lot of stuff already given and supply some new tid-bits. Your appreciation of the 44XLS HV feedthrough info is well received. I will admit that I had the devil's own time finding a non (R) resistor version, but a sympathetic parts counter man ordered 10 for me. I have taken mine to nearly 30kv with no break down. I use a silicone boot over the plug to avoid breakdown along the insulator in air and avoid moisture and dust build up there. I honestly believe 40 kv would be doable if the boot also was loaded with HV silicone putty, letting it ooze out as the item is slipped on. Air, dust and moisture are the defeaters of insulation. In my next system I will have to use a formal weldment type vacuum rated HV insulator which I already have on hand.

Your comments about looking back over the old postings is sage advise. Those postings contain a lot of gems of knowledge often hard won and a load of website pointers. The bad thing is, website pointers are like beach sand, they shift and change rapidly and many sites just disappear. Too bad. A lot of the old government lab sites had a quick lockdown on certain info after the chinese espionage freak-out.

Richard Hull