How To Make A High Voltage Measurement Probe For Your DMM!
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- เผยแพร่เมื่อ 29 ก.ค. 2015
- How to make a high voltage measuring probe so you can measure THOUSANDS of volts using an ordinary digital multimeter. The DIY/Homemade probe shown in this video can measure up to 20kV Peak using your DMM. Enjoy the video!
DISCLAIMER: All high voltage circuits, projects, or devices shown on this channel are to be made and/or used at the viewers own risk. Know your abilities. When measuring high voltage, ONLY use one hand, and wear thick rubber gloves for added protection against shocks or electrocution. This channel will not be held liable for the use or misuse of this device which results in property damage, injuries, or death.
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thanks, now this one I will definitely build! its a good thing to have in your bag of tricks.
Love your videos, very well done! I made this probe and used it to check x-ray transformers, always wondered how to do it. 70,000 volts! Used two high voltage resistors (1.250,000) due to the fact the terminals are above and below ground. Also put a small pc mount variable resistor on the ground end so I could adjust and correct the voltage. Thanks again!!!
+wolfgang schmittenhammer
Glad you enjoy my videos! Not enough people are watching them. Please be sure to share and rate thumbs up. Thanks.
What is 1.250,000 ?,terminals above and below ground?, why you used pot and watt of it?
You do a good job of explaining and displaying the subject. I give you an A+
Thank you! Be sure to check out my extensive video playlists for other great videos of interest to you. Also be sure to share my channel with friends.
always good, thank you ...
I saw something similar in 'Lucid Science' but there first goes measuring the meter's own resistance to be sure of valid reading at the end. Like adjusting the resistor not only to the multiplication we are interested in but also to meter's mechanics.
Nice project, i made mine with a grabber on the tip, so that i don't have to touch it while doing the measurement. This gives some extra safety margin!
I used a cascade of many 10 Meg resistors and potted them in a teflon tube ,instead of the single high value resistor!
Whatever works for you! Thanks for watching
It should be noted this will work best only with meters with high Z (impedance) inputs. Luckily most DMM's have input Z's around 10Mohm so it can be negligible in some cases.
Also be careful to NEVER connect the negative ground of this probe to the high voltage line. This will connect the meter directly to the HV, and if that HV is relative to ground as you are, than you will get a nasty shock reaching to the meter, esp. if it is a cheap dangerous (without proper CATII 1000v CAT3600v rating or better.) one as the one shown in the video.
Power Max I mentioned in the video exactly where the HV is applied to the probe, but you are correct, I can see people connecting it up backwards, which is why I added the disclaimer to the video description area. You're also correct regarding the 10M DMM inputs.
Thanks For Watching
Very useful probe I will be making some for our workstations, thank you and I have subscribed.
It is. Thanks for watching. Be sure to check out my extensive video playlists and share.
Thank you.
AkaMrJay You're Welcome! Thanks for sharing.
❤❤great video simply diy
Great video :) Very useful probe, actually. Sometimes I repair CRT TV's, so such a probe is a nice thing to have. It should be rated for 30-40kV, but overall it is gonna be the same
MrJohhhnnnyyy Glad you enjoyed the video. You can pick up 30-40KV resistors online.
electronicsNmore what happens if the resistor fails could it fail in a way that it has potential for high voltage to be on the probe wires ? Newbie I am !
Anything is possible, which is why it is a good practice to not hold the probe. The resistor is designed specifically for high voltage use, so failure is unlikely if you stay below the maximum rating of the HV resistor.
Clear concise video. I hope I am not too late to ask a question, which is: can I use two 49.9M 1W 10kV resistors with my DMM or is 1W too low for this application? I was trying to work out the current my DMM would use so I could calculate this but I don't know my DMM's current draw.
I answer questions on all my videos regardless of age. Using (2) HV resistors in series to get the correct resistance value is fine, but use the wattage stated in the video, or very close to it.
@@electronicsNmore Okay, got it. Thank you. =)
How would you measure voltage from distribution transformer with this when there is 3 poles all positive at the HV end? I have one 50kVa D-TRAFO in my shed, i have built ballasts for it and resonant capacitor bank. Just want to measure the differences between each updates i make to find the right resonance. Thanks! and don't worry i wont hold the probe when measuring it, not that stupid that would go near to it when its on and there is charge in capacitors.
Thanks so much. Can I use it to measure high voltage high frequency such as fly back transformer?
As long as the DMM is designed for the frequency, and the components used are rated for the high voltage. Thanks for watching!
can you use it. to check automotive pick up coils?
WILLY MANSILLA The components used would need to be rated for higher voltage.
Love your videos. I work in a lab and am a relative newbie to electrical systems. I need to measure the current going to the magnetron. Would the high voltage probe allow me to do that?
Hello. The probe is only for measuring voltage, not current. Magnetron current is around 300-400mA. A current clamp around the WELL INSULATED HV wire leaving the transformer before it's connected to the capacitor and diode. That should work.
Thanks! My setup is a bit different. We are using an Alter power supply in conjunction with a transformer. 208V comes in from the building and is split between the power supply and the transformer. The transformer in this case actually steps down the voltage to ~4.5V to supply the magnetron filament. The power supply steps up the voltage to the 4kV required for our 1.26kW system.
I would like to use this voltage divider design for useing in for my oscoop probe to look at Flyback outputs and see what it looks like related tot the oscilated input of the flyback. Would this be possible without using the complecated diy probes that use all kind of capacitators. I am only interested in the wave forms and the relation between the driver, so accuracy is for me also no issues. So would your design be applicable for that?
I would think as long as you don't exceed the voltage rating of the probe components, you should be fine. If you don't destroy a cheapo DMM measuring the output voltage, then it shouldn't damage the Oscope.....but there's no guarantee. Try at your own risk. Thanks for watching!
@@electronicsNmore Yes, that's a good safety measure I think. Put a HV capacitor on it so it will boost the voltage to the maximum and than measure it with a DMM. If that's safe (the DMM is still fine) I could maybe go for a measurement with the oscope. But I'll be honest with you, I'm a bit scared; I do this hobby just for 7 months now and I have the scope just for a few months, so I will take some time I think. Thanks :)
What is the black thing we see coming out of the pencil to the 200Kohms resistor?
Hello. Inside the end of the pen is a plastic plug with a small copper nail in the center. :-)
How about connect one 100Megaohm and volt meter in serial, use multimeter's internal resistance to get low volt reading and calculate racial?
I wouldn't change what I did.
Why you didn't add capacitors over resistors?
Do you have instruction on how to make this probes with parts also thanks
+alsteven44
Hi there. The design was well explained in the video. Be sure to use the proper rated components.
Thanks For Watching!
Hi!
I would like to measure small RF voltages..
Do those resistors voltage dividers are ok to measure 25kHz to 100kHz AC (2kv to 20kv..)
From which frequencies Capacitors dividers are usually used ?
Thanks for your answer.
Sorry for bad English :-)
The voltage divider itself should be fine, but most meters will not accurately measure AC in the kHz range; they're designed to measure AC at 50-60 Hz.
Nice video, thanks! Why does the second resistor need to be > 1/2 watt?
In your case, Rb=200M, Rs=200K, a factor of 1000. Say you go crazy and measure 100KV -> then Rs sees 100Volts. Dissipates 100^2/200000=0.05w. A 1/4 watt resistor can take 5 times that. 20 times if you measure 50KV.
It's been a while, I think it was 1/2W. Thanks for watching
Here you have used 200M 8watt but 5watt will do?
Should work OK.
Hi, This voltage is for AC or DC only?
What's the exact name of the pencil?
Hello Jean. All information should be in the video or video description area. I use the probe for pulsed DC or AC.
Would a 5W 1GigaOhm 1% Tolerance Glass Glaze Film Resistor + 1kOhm metal fim resistor work? That would make it possible to read up to 1GV?
Needs to be high voltage rated.
Thanks for the swift reply.
I was looking at these resistors:
www.aliexpress.com/item/5W-1G-Ohm-1-Tolerance-Axial-Leads-High-Voltage-Glass-Glaze-Resistor/32718623136.html
www.aliexpress.com/item/1LOT-100PCS-Metal-Film-Axial-Resistors-1Kohm-1001-1-1W-1000ohm-resistor/32524713943.html
@@defooraap If you use a 1G ohm resistor, you have to use for R2 = 1M ohm (and not 1K ohm...) ( better 200M and 200k)
(for people who want to build this (1 year later...))
What type of wire do I need for input voltages as high as 20kV?
Silicone
@@electronicsNmore Thanks!
So you have created a voltage divider, am i right or am i missing something.??
Thanks for the video anyways.
Great DIY but seen something that I myself would have a problem with if I made one. Your two meter wires off the probe are short (length), they are the same length and not isolated from each other. If you had it all connected and turned power on to measure HV and something moved or vibrated (like a large unmounted transformer ect) there is a good possibility that they will touch and ruin your day. (or even connecting them and having them on top of a conductive surface).
***** You are correct that I should have made the wires different lengths to prevent them from touching each other, but even if they did touch, it would be a non-event. At 20KV using a 200M resistor, only micro amps can pass. If the red clip shorts to the ground clip, then you will have no current at all to measure.
Thanks For Watching!
Hi, I can't find this resistor on ebay or bangwood. Besides, it could cost 30$ or more.....
I bought the resistor on Ebay. Try using Google product search.
I am not able to know that why high voltage resistor is used,if we use a typical resistor with proper wattage using p=v^2/r .will do?or if we are using high voltage resistor because of wattage is not the issue.
wattage is not the issue. Resistors have a voltage rating. Checkout the specs on carbon, wire wound and metal film. 1/2 watt carbon resistors are usually rated at 500 volts.
@@dri50 you mean power is nothing do with voltage ie
p=v^2 /r has no meaning,only for considering current power is calculated ie p=i^2 * r. I mean to say that if you use 12 resistors in series voltage across each resistor will be supply voltage divided by 12 then voltage will not be issue. ie 10000v/12=833v. This can be measured at 1000v range.
The problem with using several carbon resisters in series is that if only 1 fails (say it shorts) then all the other resisters are subjected to a much higher voltage and they may fail. Since your hand is on the HV probe this is not a good situation.
also, there is very little current flowing in the probe. Maybe only 50 microamps
Awesome!!!!
Anthony Volkman Glad you enjoyed it! Be sure to rate thumbs up and share.
Is this work with fluke 87
+alsteven44
Should work fine.
Thanks for watching!
N more
Pls
Plenty of Nmore on my channel. LOL
I want to be able to measure 100kv
I think the probe should be made longer and be held by a part that does not contain any elements. I would bet it will arc over easily before reaching 20kv. 2.5kv test does not prove anything. Even tektronics p6015 probe needs some oil inside to reach 20kV. It may not happen every time, but sooner or later voltage will find its way.
If you're concerned, add a thicker layer of protection between the probe body and your hand. Thanks for watching!
you should actually market a reasonable priced HV probe thanks.
Thanks for watching Jim! I have a lot of excellent videos on my channel that cover many different subjects, so be sure to check out my extensive video playlists for other videos of interest to you, rate thumbs up, and share my channel with others.
What are those cables rated for? 1K? Where's the safety margin ?
Adrian Higgins You do realize the wires do not need to be rated high voltage? Once the high voltage crosses the 200M resistor, the voltage is at a very low level as you saw in the video. All that needs to be high voltage rated is the plastic tube, and the resistor. If you feel the need to have high voltage rated wires for low voltage use, then you can remove the HV wire going from the flyback on a CRTV to the tube and use that. They are usually rated 40KV.
electronicsNmore Could you check your video from around 2 minute mark. You were referring to resistances etc. Seemed to be jumping around between Meg ohms and kilohms. I think there may be an error there. (I'd like you to check it in case someone builds on of these and makes a mistake etc).
Great video - Thanks v much.
Everything is correct. I watched it before uploading. There are (2) resistors used to make the voltage divider. One is MEG ohms, and the other is KILO Ohms. There is also another image in the video showing the voltage divider.
electronicsNmore Oh, of course, you are making a voltage divider with a voltage drop of 99.9% roughly across the first resistor.
Sorry - I wasn't paying attention, obviously. (I'm also not very smart with these kinda things).
Thanks v much for reply. Great stuff.
Should be called the Death probe.
It's a very safe HV probe when made properly and used with the correct voltage. The part you hold is made of plastic as well.
@@electronicsNmore Sure, let kids poke the microwave oven terminals with this. What's the correct voltage btw?
But the resistence of the multimeter is 10Mohms and others are less
What does that have to do with anything? I proved the probe works.
i was asking if that is 10 mohm or less
Most DMM's have a 10M input impedance.
If you value your life, don't EVER measure high voltage while holding a probe in each hand!
Put an alligator clip on that black lead and only hold the HV probe in one hand with the other hand in your pocket.
Do not let your stomach or any other part of your body touch any conductive surfaces and wear shoes; preferably ones with rubber soles when using the probe.
Not following those safety guidelines can get you dead!
One mistake could easily be your last!
Where exactly did you see me do that in the video for high voltage?
@@electronicsNmore No, you didn't show it. But left a lot of space for dumb errors from the part of your users/viewers.
Moreover, you suggested that this could go up to 40 KV. are you nut?
This is probably so unsafe
A high voltage dmm probe on a test gear site is like 75 bucks
I'd say someone's life is worth a lot more than 75 bucks (or just don't mess with high voltage for fun)
Nothing unsafe about it.
@@electronicsNmore The clearance between the body and the item to measure is very unsafe. The HV probes are very long
First of all 30kv is medium voltage not high voltage. Second this is an interesting idea but I strongly suggest not to actually try this probe on a medium voltage circuit. (I wouldn’t use this on a 2kv circuit) If it arcs over the explosion will probably kill or maim you! Medium voltage switchgear is not something to play around with get proper tools please.
Don't be a pedant.
There are too many dumb things you did here. If anyone would put this together they should not go more than 2 kV, but not 1 kW microwave oven transformers.
You started very scientifically by mentioning dielectrics of the pencils and then go full dumb mode suggesting short resistors, and then soldering them like there is no tomorrow, ignoring everything related to air. and, of course, air bubbles in the materials.
The only dumb things are what come out of some viewer's mouths. The high voltage makes contact with a LONG 200M resistor which happens to be very snug inside an excellent dielectric tube. What I did after the 200M resistor makes no difference. Think before speaking next time.
@@electronicsNmore One usually builds a HV probe using the high resistance resistor and the resistance of the meter itself. Then, all the design goes into the plastic around it. How do you know the dielectric value of the plastic of that pencil? Did you measure it? Do you have some idea of the air bubble content of that plastic, which will turn out to be the failure point of that "probe"? I don't care if you'll find out the hard way how this probe will fail at 20 kV while using it yourself, just don't tell others that it's safe to use, cause it's not.