Electronics > Projects, Designs, and Technical Stuff

Open HV Probe 40kV

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vk6zgo:
I'd like to have one of these:-
https://www.ebay.com.au/itm/L-M-Ericsson-Pty-Ltd-Trimax-Division-Model-52C-Ionisation-Tester-Type-G1B-/202602664145

Just about everywhere I worked had one, so there were plenty around.
The eBay one is a bit too costly for me, though!
Grays Online auctions have one, too, but they always insanely overprice everything.

beanflying:

--- Quote from: ArthurDent on April 23, 2019, 09:10:46 pm ---Warning! If I recall correctly, a neon sign transformer that has an output above about 7.5KV has a secondary that is centertapped and the centertap is grounded to the metal base. If you plan to use a neon sign transformer, then check it out to see if this is the case. I don't have a neon sign transformer but check it out before you power up the transformer. Oil burner igniter transformers may be centertap grounded as well.  If you have a c.t. transformer and connect your meter common lead to one of the transformer terminals you could have a big problem.

Google it for more info. Also trying to disconnect the c.t. and ground one of the output terminals can cause transformer insulation failure

--- End quote ---

You are correct at least in the case of mine about the centretap. While that information is available fairly easily it might be a good idea to add some additional appropriate safety information/links on HV probe use and safety but there are a lot of testing cases to cover. There is also a lot of bad information out there to try and counter  :palm:

beanflying:
Just a few design details on the handle end. Currently takes 80x20mm PCB's with plenty of room above the board location and is setup for a small cable gland on the bottom. I might change the sizing and part for it as some idiot used a 13x1.25mm thread pitch on this one :horse:  :rant: :wtf: :horse: Creating non standard threads in Fusion is a PITA!

joeqsmith:
I was thinking just start by applying the signal across the two ends of an empty probe body and see if you can measure any current through it.   

If you have an electrometer, maybe try and measure it that way.   

Yes that shield on my probe is there for noise and prevent coupling to any stray objects.  It has nothing to do with safety.   Even the GDTs are not there for safety.  My only concern is to protect the scope's front end.   

beanflying:
Really Quick and dirty test at 1kV AC and DC uncoated and uncleaned after being handled trimmed/sanded etc by me without gloves. Poor leads and poor technique ;)

DC 0.00mA @ 1kV.
AC @50Hz 1kV 0.00mA
AC @1kHz 1kV 0.24mA

Given the setup that stray current may be coming from elsewhere into the 121GW other than via the Valhalla. That said the Valhalla needs a Cap replacement and a proper going over and I haven't hooked up my Micsig HV probe to look at the wave at higher voltages. My 344501A and 34461A are not back from Keysight Cal yet (should have them next week). May is Recalibration and testing month for the fleet.

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