Cheap vacuum gauge ZJ-52T / KF10

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.
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Jaron_Veld
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Cheap vacuum gauge ZJ-52T / KF10

Post by Jaron_Veld »

Hi guy's

I like cheap equipment and saw these Pirani style vacuum gauges on aliexpress called the ZJ-52T.
Is anyone using these for their system? The actual reader for it is way to expensive but making the electronics for it shouln't be to hard I'd imagine. (Designing would be most of the effort)

Does anyone have experience with them? Do they need calibaration? How good are they without calibration?

BTW, if anyone is using the ZJ-27 Ionization gauge i'd also love to hear so. Bought both and would like to make some electronics for them and share it so everyone can use these cheaper gauges. :)
Jerry Biehler
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Jerry Biehler »

Unless you live close to china or have a ready source of replacement tubes you are probable better off just going with the standard tubes that have been around for decades and are everywhere and carried by all the suppliers. Same thing with that ion gauge tube. You need the specs to get the settings right for the controller.

Id just pick up a used MKS 901P like others have done here.
Rex Allers
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Rex Allers »

Jerry suggested getting an MKS 901p. It is a great vacuum sensor for atmospheric to just below 1 micron. It can be used with analog voltage output or serial data command/response. In the latter the probe does all the work to give a text value of vacuum and is configurable for units: ("Torr", "mbar", "pascal") or selected gas curves: ("Nitrogen", "Air", "Argon", "Helium", "Hydrogen", "H2O", "Neon", "CO2", "Xenon"). I got a couple of them.

Lots of info on this forum from about 5 yrs back.

Here's a pic
MKS-901p.jpg

Now to report some bad news. Around 5 years ago many of us got a 901p as there were many nice clean ones listed on ebay for around $50 or less. Several months back I checked ebay and there weren't many listed and prices were $100 or more; very few from US sellers.

I looked again today and no great deals like 5 yrs ago. Cheapest I saw was $75 and it had obvious physical damage, possibly signs of being opened up. Most listings were from Asia. Many have a VCR vacuum fitting. Nothing wrong with that but a bit more hassle than the KF16 on most of the ones from 5 yrs ago.

There's a new style of 901p in most of the listings. It has a longer cylindrical body. I haven't tried to search for info but I would guess it is a newer design that works the same as the ones we got earlier.

There's currently one of these, newer style, KF connector, from Michigan, listed at $120. That looks to me like the best buy right now. The newer style is a bit of an unknown to me, though. Anyone know if they work the same as the older smaller ones?
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Sophie Yang
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Sophie Yang »

Zj27 and ZJ52 are widely used in China, we can often buy new ones for 10-20 USD. But they are very old products, and their technology is very backward. Therefore, the range, accuracy and other performances of this series vacuum gauges are worse than modern products.
Take ZJ27 as an example. It is not a B-A gauge that we often see, but a very old hot filaments ionization gauge. The collector of ZJ27 is designed outside the grid, which will cause it to only measure the pressure of - 7Torr.
Chinese vacuum gauge controllers often like to integrate zj52 and zj27 to form a full range measurement system. But in fact, their performance is much worse than PKR361/251. These cold cathode composite gauges have higher accuracy and can measure lower pressure without considering filament burn out.
But if you want to design a controller for your zj27, it is also very simple. Its grid voltage is 200-225V, the collector is 0V, the emission current is set to 1mA, and the sensitivity is 15 ± 15% mbar ⁻ ¹, By specifying these parameters, you can use them to read the pressure accurately. However, it should be noted that zj27 cannot be started at a pressure higher than 1E-2mbar, otherwise the filament will burn out, so this gauge is not suitable for fuser.
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Sophie Yang
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Sophie Yang »

MKS901P is a good choice, but this kind of micro pirani gauge based on MEMS does not have a real gold-plated filament, which make them particularly vulnerable to being polluted and inaccurate by the unclean vacuum environment. Common models of MKSvacuum gauge can be found on the official website.
7543DBD6-F11A-41A1-A177-1718C446AEB4.jpeg
62DF6AF2-A3AB-4FB4-A4AB-0C7BAA232220.jpeg
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Richard Hull
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Richard Hull »

Thank you, Sophie, for the full and accurate description of the Chinese gauge systems that are the subject of this thread. It is appreciated.

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
Robert Clarke
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Robert Clarke »

By coincidence I'm currently trying ( and failing ) to build a controller and readout for a zj-27.
I've hit a brick wall with getting the ' collectrode' ion current to register on a op amp in the current to voltage configuration.
@jaron_veld, or others, would you be interested in collaborating on an open source controller for this?
Robert Clarke
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Robert Clarke »

For your delight or dismay I have attached a picture of where it is at now.
Attachments
Zj-27 DIY controller vacuum gauge
Zj-27 DIY controller vacuum gauge
Aleksa Djokic
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Aleksa Djokic »

I have successfully built several BA readout/controller circuits without any hassle. Are you using a low input bias current OP amp(electrometer)? If you have 180-200v on the electrode, 30v bias on the heater and a stable emission current of 1mA, you should be go to go. The output of the collector electrode should go directly to the electrometer input.
Robert Clarke
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Robert Clarke »

Hi Aleska, thanks for the response.
I'm trying an Lm358. Unfortunately my knowledge of op amps is limited. So this is a random choice I admit.

My apologies for the noob question. But if I was looking at the data sheet how is the low input bias described? Is it just Ohms? Or should I be looking for other terms?
I'm excited to hear it is possible to build from scratch!

I believe my voltages are pretty close to the official zj-27 recommend, so my current should be in the 0.1mA area assuming the tube is sealed at a very high vacuum level.

Any op amp recommendations are welcomed!
Aleksa Djokic
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Aleksa Djokic »

Well, if this is your first encounter with op amps, maybe start with something simpler. You will need at least two separate op amp circuits to drive and measure the current out of the gauge.

LM358 can be used as a servo controller for the filament control and emission current.
For reading the collector current, something like LMC622, I personally have used ICH8500A, aside from electrometer op amps, to form the actual circuit, you will need high value resistors and also high quality, something in the range of 100M to 1Gohm will do the job, depends on the desired measuring range.

From the pictures you provided, I don't see a circuit that regulates the emission current. To get emission from cathode(filament) to anode (first grid/electrode), you need a servo loop that constantly measures emission current and adjusts filament output to maintain exactly 1mA. The 180-200v can be unregulated, just needs to stay within the range and not have any ripple. Also, I do not know if the gauges are vacuum sealed, maybe Sophie can elaborate more on this, because if they are just rough vacuumed, you are probably damaging your filament.

Here is a example of constant current source that you will have to make in order to have constant emission.

https://www.bristolwatch.com/ele3/ccs/ccs3.jpg
RobertMendelsohn
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by RobertMendelsohn »

To add my two cents, I have owned two MKS 901P: after a much-frustrating leak finding process, I discovered that the 901P was leaking. I then got a replacement, which also leaked. YMMV.
Robert Clarke
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Robert Clarke »

Aleksa, wow that has clarified many things for me.

I had understood that the 0.1/1mA of the documentation was what I would see from Ion Current!
So this is electron current from the filament! An so it it 'safe' for filament to supply electron current up to 1mA?
I had understood it was filament (heating)current to ion Current that were the parameters to be considered!

Thank you for the electrometer op amp recommendations.

I have pulled a few high ohm resistors from microwave oven capacitors. Not sure they will be ok, probably not very high quality! I'll check what they are when I get back.

Regarding vacuum level in the tube, I have my fingers crossed...and another tube ordered!

So my setup is not ideal...

As way of a description of what I had in mind was as follows. That test tube is my DIY 1Ohm power resistor. The SMPS is 3.3v 6amp with a small trim pot giving about 1v of adjustment. I had planned on adjusting that to 1.3v across filament and hopefully that would be 2.5amps but I see now this is not... optimal.

I will look for ripple on my high voltage supply. I have a hand held oscilloscope that I guess will see if it's truly horrible.

Many thanks for the link. I will inspect it.

Would you mind if I keep this thread alive? I have been working on this for a few weeks and the bigger project for years and learning so much. I am determined to make it work!
Aleksa Djokic
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Aleksa Djokic »

I would strongly suggest for you to make a new thread, there are probably many more interested in the same topic, and I can assure you, there are some real experts in this field on this forum, just take a look at this thread: viewtopic.php?t=13905
Robert Clarke
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Robert Clarke »

Yes absolutely. A new thread makes sense as I have diverted this one away from it's title, which is a little confusing. I'll put a link below once it is established.
Lots of interesting information in the mass spectrometer build linked above also. I had not fully appreciated how electrically noisy the world is when trying to examine those tiny currents
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Richard Hull
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Re: Cheap vacuum gauge ZJ-52T / KF10

Post by Richard Hull »

An electrometer opens up a new vista and understanding of how millions of tiny currents flow everywhere in an active and dynamic world environment. Charges are in constant exchange that only an electrometer or low picoamp and preferably a fempto ampere input op amp can detect and make visible to us.

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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