Kurt J. Lesker 275i series - Seems like a great buy!

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Adam Szendrey
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Kurt J. Lesker 275i series - Seems like a great buy!

Post by Adam Szendrey »

So I searched around on the internet for a good deal on a suitable vacuum gauge. On ebay I couldn't really find what I wanted, and I kind of felt that in a lot of cases I'd have no idea if the gauge and controller are actually calibrated. I know it's not critical, but I prefer instrumentation that I can rely on.

Then I stumbled across Kurt J. Lesker, and browsed their gauge selection a bit and came across this beauty :

Image
http://www.lesker.com/newweb/gauges/con ... kjlc_2.cfm

I did a quick search of the fusor forums and found that some actually use the 275 series from Granville-Phillips ("mini convectron"), I couldn't find anyone using the 275i, so I figured I'd post this. I feel that the fact that it has the controller (has a nice LED display) built in,has a log-lin analog output, and even a relay contact, makes this a VERY good buy at just under 300 USD (with a KF25 fitting, it's a bit cheaper with KF16)! Most (used) pirani heads on ebay cost that much alone from what I've seen... I didn't even bother looking at brand new gauges because I thought they are much more expensive..Well I was wrong thankfully! And it goes down into the 1e-4 range, making it pretty much ideal for fusor work. You just slap it onto your system, power it, and you are set. Gauges from Pfeiffer for example, having a similar range cost a LOT more, well above a thousand dollars , with the controller. I'm planning on buying one of these in the coming months.

If anyone here has some hands on with the 275i (this specific product), then please let me know!
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Jerry Biehler »

They are a replacement for the Granville Phillips 275 gauges which you can get a lot cheaper on ebay, like this:

http://www.ebay.com/itm/Granville-Phill ... 51c95858ce
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Jack Puntawong »

Great find! I thought a new gauge like this would be between $500-600 range. However, they are charging $60 for a power supply. I would imagine that we can use a 12V or 24V adapter for this. I would like to know how this function as well. From my experience, getting a workable gauge is the most important step toward fusor. With out a good gauge, you don't know whether your pump is working properly or whether your system is leaking. I'll rather spend more money on a calibrated gauge than a used gauge which might not be working.
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Richard Hester »

Convectron gauges and controllers are cheap enough on E-pay - it's the cables that'll get you, though I suppose I could improvise using some multi-conductor wire and individual female contacts w/heatshrink.
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Jerry Biehler »

Its just a DB9, get an old serial cable and chop one end off wire up power. A serial cable is only a few bucks. Or you can buy a female DB9 connector with solder cups and make your own.

The one thing you need to be careful about is the gauge orientation, it must be horizontal in it's long axis or the readings will be wrong. It uses convection to measure vacuum.
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Adam Szendrey »

Jerry, I should add a bit more info to clarify! Yes you can find the mini convectron on ebay, but since I live in the EU, and pretty much all of those gauges would ship from the US, shipment, VAT, and customs would apply, which would bring the price pretty close to a brand new 275i, if not over. KJL has free shipping and ha a warehouse within the EU (no shipping cost, no VAT, no customs).If not a lot more expensive, I'd prefer a new instead of a used gauge, since I have no idea about the service history of the latter. But I will keep poking around to see if there are EU deals for a mini convectron (with a display).

Richard, I'd say the cable is pretty much a non issue. The pinout of the DB9 on the gauge is available in the manual (I checked), so no need to buy a 70 dollar cable+power supply (horribly overpriced). You just need the cheapest 12 V DC plug-type supply and a serial cable, as Jerry pointed out. Or alternatively you can get a female DB9 (they are very cheap), and solder a cable to it (although buying the complete cable and chopping one end off is the cheapest, a couple dollars). This is why I really like the fact that the controller is integrated into the gauge by the way. Even simpler to make the cable (just a "power cord" pretty much). And of course you can use a simple ADC to digitize/log the output of the gauge, so you don't loose any functionality either (or very little, compared to a separate controller setup). Also the log-lin output makes it quite easy to process the data from the ADC. I think the original mini convectron has a non linear output (I might be wrong tho!).
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Richard Hester »

D-shell connectors don't work for the classic Convectron gauge - they use some sort of &**### proprietary connector (G-P uses the same/similar connector for their ion gauges.. The Mini-Convectrons may be another matter, however. I have both around the house, though I can more readily lay my hands on my standard Convectron tubes. The classic G-P readouts (both analog and digital) use a PC edge connector (I forget how many positions) - easy enough to bodge.
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Adam Szendrey »

Luckily the 275i, listed here, uses a standard connector. At least it says so in the specs list: "9-pin sub-D (male)". The other mini convectrons (275, without the "i") which don't have the built in controller use some sort of round special connector (see http://www.lesker.com/newweb/gauges/con ... kjlc_4.cfm). When you buy the 275i you get a much better value than buying the head plus a separate controller.
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Richard Hull »

I haven't looked into this, but the digital readout in the end of the gauge is fully mechanized within the assembly itself and doesn't require anything other than external power. Is this correct?

I realize there is probably a serial line in the DB-9 designed to send data to a custom and expesive controller that will remote read and data log and communicate with computers, etc. But the gauge itself, as seen in the image, does not require this control to return data to the digital read out on the gauge. Correct?

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Adam Szendrey
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Re: Kurt J. Lesker 275i series - Seems like a great buy!

Post by Adam Szendrey »

Exactly, except for the serial link. It has the following in/out pins on the DB9:
Analog out: log-linear 1 to 8 Vdc , 1 V/decade or non-linear analog S-curve 0.375 to 5.659 Vdc (Mini-Convectron Equivalent), user selectable
Relay switch: One SPDT relay 1A at 30 VDC resistive or AC non-inductive, you can set this to any setpoint
Power input: 11-30 VDC, 2 W, protected against power reversal, transients, over-voltages

So yes, if you simply give it power it will work, but it has some extra features one can use. You don't need an external controller for any of those either, making this a fully self contained unit (the display automatically switches between torr and mtorr as the pressure drops).The gauge can be configured with the small control switch on it's side. You can connect your own ADC to the DB9 to get the data into a logger or your computer, or whatever. They pretty much took the external controller and put it inside the casing of the head. This is why I fell in love with it, simple, good range, good price, and a couple of very nice extra features. And the fact that I can order it from within the EU, totally hassle free, without extra fees (even free shipping).
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