Thermal Camera vs Milliohm Meter for short finding? - Page 1
Forum section: electronics / repair

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 01:12:43 pm
content: I'd rather only invest in one of them for now, which one would you recommend for short finding in repair jobs? Voltage injection + thermal camera or finding the short with a milliohm meter? Can you also recommend the cheapest device that you'd consider worthwhile for the task? On AliExpress it seems you can get an Ok looking thermal imager for ~150EUR and a milliohm meter for ~100EUR.

author: RoGeorge
author_rank: Super Contributor
timestamp: August 27, 2023, 01:42:25 pm
content: A thermal camera is more useful, because a defect is not always a solid short to be detected, can be a component not that shorted but only heating more than usual.Then, a "shorty" detector is easy to improvise, there are various examples online if you search the terms. They can be easily built in a weekend at most, while a thermal camera is not something one can DIY.

author: MadTux
author_rank: Frequent Contributor
timestamp: August 27, 2023, 01:45:14 pm
content: A couple of Amps from PSU and about any 6 1/2 digit DVM does the job, as m/µohm-meter.Inject voltage limited current on short and measure voltage drop, same as 4wire Ohm measurement, but with much more current, i.e. more voltage drop and more precision.Thermal cam gives you the area with most resistance, that might or might not be the shorted part.

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 01:54:41 pm
content: for finding shorts, nothing is better than the "shorty-with-display" ...and it's cheap to make yourself too.http://kripton2035.free.fr/Projects/shorty-display.html

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 01:58:27 pm
content: What exactly is this 'shorty' device? Is it just a milliohm meter?I don't have a 6 1/2 digit DMM and I think buying one would be more expensive than the other two devices.Can you recommend a cheap thermal imager that is still useful for repair tasks?

author: RoGeorge
author_rank: Super Contributor
timestamp: August 27, 2023, 02:09:33 pm
content: Quote from: Rooster Cogburn on August 27, 2023, 01:58:27 pmKind of, but with an audio indicator, faster and easier to use than looking at a display and reading numbers.https://hackaday.io/project/3635-shorty-short-circuit-finder

author: Gyro
author_rank: Super Contributor
timestamp: August 27, 2023, 02:14:44 pm
content: Yes, a shorty is effectively just a milliohm meter.Build yourself a simple milliohmmeter If accuracy isn't important then just make a current source with an LM317 and a couple of clip leads, or use the bench PSU curent limit. The most basic 3 1/2 digit DMMs have at least a 200mV range. With a current source set at 1A, the 200mV range will read up to 200mOhms with a sensitivity (after the decimal point) of 100uOhms. If you want higher sensitivity then build a simple x10 or x100 Opamp stage. The input impedance is going to low, so use a bipolar opamp rather than CMOS. Pick one with offset null pins so that you can trim it for a 0 reading.The important thing is Kelvin sensing (not sharing the Current and Voltage points). Clip the current leads across the the board supply (or wherever you have the short) and then probe around the points on those nets until you get the lowest mV reading.You can build something like that for <$5 and save your money for a Thermal Camera - which might actually be a less sensitive method unless you crank the current up.P.S. You don't need a 6 1/2 digit meter, a 3 1/2 or 4 1/2 meter with a 20mV range would be just as good for this.... The Aneg 8009 comes to mind, it's cheap, has a 10mV range and is supposed to have a 1uV (1uOhm @1A) resolution, although I think it has a dead zone below 5uV.

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 04:23:28 pm
content: Hm, seems like people here are also divided between thermal imaging and resistance based methods :/I have a Fluke 17B+, which is a 3 1/2 digit meter and kinda useless for anything <1Ohm. I have a Peak ESR meter that goes down to 0.01Ohm but is also limited by being 2-wire.The shorty seems like a really neat device, but I'm not really up for a project like this. It involves an Arduino and I'd have to get a case for it etc., I'd rather just buy some kind of meter.These Vici VC480C+ meters seem neat:Specs:https://ae01.alicdn.com/kf/S591a11dab36649c0a22daf906bf89603w.jpgThere's also the YR2050:The probes are kinda useless with both of them, not sure how cheap/available 4-wire sharp-tipped probes are. Here's a review of both devices from Learn Electronics Repair:(Haven't watched it yet!) Edit: Just watched it. The Vici seems like a decent choice, too bad it's so bulky and the probes are also bulky :/As far as thermal imagers the UNI-T ones seem good, but are somewhat expensive. There's the knock-off looking Noyafa NF-521 for ~150EUR:The cheaper sub-100EUR options all look a bit useless.

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 05:13:25 pm
content: what about this one :https://www.aliexpress.com/item/1005005441679117.htmlor this one :https://www.aliexpress.com/item/1005003219839921.html

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 05:16:26 pm
content: I would still make my own set of probes, reusing a multimeter set of probes and adding 4-wire connection.the provided kelvin probes are not ideal for short-circuit searching.

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 05:21:12 pm
content: I bought these some times ago to make my own 4wires probeshttps://www.ebay.com/itm/224967965835

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 05:39:46 pm
content: Those cheaper meters seem to be missing a zero/calibration function? Guess they would still be usable for short finding, we're only interested in the relative values...Seems like making my own probes wouldn't be too hard, but I don't really know much about that, like how much error would be introduced by having the current source/voltage sensing wires joined earlier etc. Can't you just buy these probes? A quick search on AliExpress didn't give any results :/

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 06:52:30 pm
content: it was quite easy to make them: just solder the wire at the end of the metal part of the probe.I used a shielded cable, and connected the shield to the ground of the meter.

author: mzzj
author_rank: Super Contributor
timestamp: August 27, 2023, 08:05:48 pm
content: Quote from: Rooster Cogburn on August 27, 2023, 01:12:43 pmThermal camera is way more usefull for repair jobs than milliohm meter. Like 100 times better in most cases.If I would have to spend 20 eur for milliohm meter or 2000 euros for thermal camera for repair purposes I'd pick the thermal camera.Ideally I'd like to have adjustable focus and manual temperature scale for pcb repair camera but with 200EUR budget you have to probably skip on both.(Focus issue can be fixed with ZnSe lens from aliexpress.)

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 08:13:27 pm
content: Quote from: kripton2035 on August 27, 2023, 06:52:30 pmHm, I can't for the life of me find sharp-tipped four wire probes or those 'DIY' ones on AliExpress. Searching for Four-wire / Kelvin probes yields nothing but those useless clamps and I don't know what the ones you linked on eBay would be called except 'DIY' and that also yields no results :/Quote from: mzzj on August 27, 2023, 08:05:48 pmCould you explain why? If you have a shorted component on a PCB, why is a thermal camera 100x better than a milliohm meter?

author: delvo
author_rank: Contributor
timestamp: August 27, 2023, 08:44:44 pm
content: You inject voltage and usually find the problem in seconds. Also in cases where I dont think it will be easy to find it with a miliohm meter.For example I had a WD15 dock with a shorted cap. One of the ones circled in the picture (not my picture, didnt take one at the time) is shorted. Can a miliohm meter find which one it is? They are all in parallel. Maybe yes but they are so close together I dont think its going to be very clear which one is shorted. I injected a little voltage and the right one just lights up.

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 08:50:58 pm
content: Quote from: delvo on August 27, 2023, 08:44:44 pmyes, you need to have a stable milliohm value and you can detect which one it issee example here :

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 09:00:57 pm
content: Quote from: kripton2035 on August 27, 2023, 08:50:58 pmConsidering that those milliohm meters use a ~100mA current, would it be only safe to use it like in the video, directly across components that are either shorted or parallel to a short? I'm just thinking simply placing one probe on ground and then poking around the circuit would have quite some destructive potential with that kind of current.Any idea what I need to search for on AliExpress to get probes like those that allow me to connect two wires to the tip?

author: mzzj
author_rank: Super Contributor
timestamp: August 27, 2023, 09:02:49 pm
content: Quote from: Rooster Cogburn on August 27, 2023, 08:13:27 pmWith milliohm meter you have to trace and check lots of components on the pcb. On multilayer board you can't even trace suspicious components but you might have to blindly measure bit of everywhere.Plus typical component shorts are not super-low ohmic in value: Looking for 0.5 ohm short on PCB means that you are trying to find difference between 0.501 ohms and 0.500 ohms.Having 10 parallel MLCC's next to each other and you might have real difficulty trying to fiqure out the shorted one with milliohm meter.With thermal camera all it takes is one look and 99% of the cases the shorted component shines like a beacon even if there is 500 components on the board.Milliohm meter has other uses (namely measuring very small resistances) but for electronic repair it's not high on priority list.Current limited power supply + cheap DMM does the same as milliohm meter for repair use.

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 09:14:09 pm
content: Ok, gotcha.Just trying to find the most economic solution that would help me in these situations. I could get that VICI meter for ~70EUR shipped but would need to figure out the probe situation, who knows if I can get some decent probes or make them myself. An actually thermal camera would be considerably more expensive, at least 150EUR, probably more. And I'd need to upgrade my bench PSU, too. Got a really crappy once. Has current limit but the thing is really janky in terms of adjustment etc.

author: kripton2035
author_rank: Super Contributor
timestamp: August 27, 2023, 09:22:47 pm
content: Quote from: Rooster Cogburn on August 27, 2023, 09:00:57 pmthe shorty-with-display illustrated here sends around 35mA of current on the probes, but at a few millivolts only.I use it often and never destroyed a device under test with it.

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 27, 2023, 11:42:55 pm
content: Quote from: kripton2035 on August 27, 2023, 09:22:47 pmSeems like the VICI is a bit more aggressive then:That seems enough to blow up an LED? ;-)How does the milivolts thing work? I would've expected these are constant current sources and hence the voltage is a function of the resistance encountered?Also could you tell me what those 'DIY' multimeter probes are called so I can order them from AliExpress and make my own Kelvin ones?

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 28, 2023, 01:45:59 am
content: I searched for like an hour, you can't buy actual 4W/Kelvin probes or any of those 'DIY' probes anywhere on AliExpress. Makes those meters kinda useless to me as I'll not be able to procure a suitable test lead.

author: aeg
author_rank: Regular Contributor
timestamp: August 28, 2023, 04:38:44 am
content: Quote from: Rooster Cogburn on August 27, 2023, 08:13:27 pmHere you go:https://www.aliexpress.com/i/2251832085353684.htmlBut I think you'd be better off getting them from the known good eBay seller.

author: kripton2035
author_rank: Super Contributor
timestamp: August 28, 2023, 05:49:35 am
content: strange that aliexpress is quite 2x the price of ebay !

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: August 28, 2023, 10:54:50 am
content: Quote from: aeg on August 28, 2023, 04:38:44 amYou're a wizard. I searched for the terms in the title, I searched for 'multimeter probes' and clicked through the pages till nothing but random unrelated crap showed up, nothing. Even when I search for the exact title of what you linked it doesn't show up anywhere in the search results. When I search logged out, I get no results for the title. But when I then set the language to 'English' (it defaults me to German) it finds the listing but only with the exact title. Searching for 'multimeter probes DIY' still yields nothing useful in the first few pages until unrelated items show up. No idea how you managed to find this listing!Pre-made Kelvin probes are either those clamps or double-tipped, which is kinda useless if you want to measure some SMD part :/Using AliExpress from Germany is nowadays a crummy experience anyway. Over half of the sellers I bought from no longer ship here due to recent changes in our import duties etc. and that packaging law. The issue with buying from eBay is that those sellers don't pre-pay VAT and the package will either be delayed for like a month+ and end up at the customs office or the carrier will collect VAT and charge a silly amount of money for it, so it's preferable to buy from AliExpress and let them handle that stuff even if the price sucks.

author: ledtester
author_rank: Super Contributor
timestamp: August 28, 2023, 11:06:06 am
content: Quote from: kripton2035 on August 28, 2023, 05:49:35 amAlso look for offerings like this:https://www.ebay.com/itm/234974237795The tips unscrew so you can replace the leads with your own wires.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: August 28, 2023, 11:21:50 am
content: Definitely thermal camera - much, much faster.Quite often it's not a short but a damaged component that is drawing more than it should, but not necessarily completely shorted - a thermal camera will show this up instantly.

author: Veteran68
author_rank: Frequent Contributor
timestamp: August 28, 2023, 02:24:15 pm
content: I concur with the thermal camera recommendation. I don't know about the performance of the cheap $150 cameras, but I've seen multiple YouTube videos of repair shops using the cheaper cameras and they work quite well.I have the Uni-T UTi690B (aka UTi260B) and like it. It's in the ~$350 range as it has higher resolution than the cheaper cameras, and I also have the macro lens for it. If you can stretch the budget I highly recommend it, but honestly if you can only have one or the other, I'd still take a cheaper thermal camera over trying to trace shorts strictly with a mOhm meter.

author: lugaw
author_rank: Regular Contributor
timestamp: August 28, 2023, 09:54:58 pm
content: Just use your vision as thermal camera with the aid of this tool

author: Veteran68
author_rank: Frequent Contributor
timestamp: August 28, 2023, 11:35:04 pm
content: Quote from: lugaw on August 28, 2023, 09:54:58 pmI've been seeing these pushed by NorthridgeFix too, but it requires you have an idea of the area where the short is, and if you know that, just use IPA which will show the same thing and requires no cleaning. This would leave flux residue everywhere and require cleanup after, so I really fail to see the usefulness? I watched a NF video yesterday where he used IPA "because it was close by" while still pitching his rosin atomizer. I honestly think it's too much trouble to disassemble, scrape rosin flakes into its reservoir, re-assemble, wait for it to heat up, apply it to the area, and then cleanup after. When you can just squirt or brush on some IPA to get the same effect, and it's self-cleaning.Even with a thermal camera (especially cheaper low resolution cameras without a macro lens) IPA is often used to zero in. For instance the camera will show you a heat blob in a densely packed area of, say, small capacitors and resistors where it's not clear from the camera which one is bad. IPA is then used in that area to isolate the shorted component.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: August 30, 2023, 10:21:41 am
content: I recently demonstrated use of the UNI-T thermal camera and Fluke DMM to find a shorted component.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: August 30, 2023, 03:51:13 pm
content: Hi Rooster Cogburn,You may also consider theShortyPENas a DIY project, with its' 3D printed Sharpie size enclosure (parts+PCB are sometimes sold by the author as a kit). Less than 50 bucks.Depending on where the short is located (part, PCB, wiring), several (and often expensive) other tools might be helpful (an hi-res IR cam is definitely among those).Sometimes you may need a high voltage Ohmmeter (many first tier brands sell those : Fluke, Benning, Chauvin-Arnoux), but PeakTech and UNI-T refs are more affordable.You may also check some sniffer tools like :- the rare and antiqueBug Hound- A non-contact current sense oscilloscope probe, reviewed by Dave :

author: Rooster Cogburn
author_rank: Regular Contributor
timestamp: September 03, 2023, 01:08:55 am
content: So, I bought a Vici VC480C+. Haven't gotten it yet. I'm not sure how much use I'll get out of it, though. My main concern is damage to the DUT. IIRC it has an OL voltage of 4.7V and uses 50mA and 100mA on the 20mO range.Any thoughts on this? How to use this safely without frying anything? I figure if I use it only on components / rails I already checked are shorted the current would obviously flow through the short, but just poking around on the board seems risky :/I did some more research on thermal imagers and the ones I'd actually want are a bit out of my price range :/ AliExpress had a sale, had some coupons etc. and the Vici was quite cheap then, I figured I'd probably get some use out of it and would like to try it on a real project and see if it helps me. If mO meter & thermal imager were similarly priced I'd have bought the latter, but oh well.Quote from: Veteran68 on August 28, 2023, 11:35:04 pmI also don't see the point of this. Why coat your board with a resin when you can just squirt some IPA on it?Quote from: TheDefpom on August 30, 2023, 10:21:41 amThat was a fun watch, I like your channel in general. That UNI-T thermal imager is neat, wish it was cheaperQuote from: timeandfrequency on August 30, 2023, 03:51:13 pmIf you could buy those various shorties devices here already finished I would've bought one, not really looking for yet another project atm :/I saw that current probe video by Dave a while ago, really fancy stuff. Before I saw that I thought only current clamps were an option for scopes. Probably out my price range, though.

author: Smoky
author_rank: Frequent Contributor
timestamp: September 03, 2023, 03:38:19 pm
content: Great video by TheDefpomA lot of good pointers demonstrated along the way to a successful repair.Those cameras seem to be worth their weight in gold too.My old Leader-302 oscilloscope project suffers from a short somewhere. It would be great to see its boards under a camera during start-up.

author: tridac
author_rank: Regular Contributor
timestamp: September 03, 2023, 03:59:52 pm
content: Don't need 6.5 digits. Any dvm that can measure millivolts should be good enough. With a 2-5 amp limit, things like shorted tant caps usually smoke or go pop, easy to identify and replace. Cheap thermal camera won't tell you very much, but I guess it sounds good :-)...

author: xavier60
author_rank: Super Contributor
timestamp: September 04, 2023, 03:34:40 am
content: It can be difficult to follow the shorted rail on multilayer boards like in laptop computers.I use 0.5A and track down the shorted part by measuring voltage drops across the ground plane.Needs uV resolution and it doesn't always work out. One tricky example is when the short is on an island of ground plane.

author: timeandfrequency
author_rank: Frequent Contributor
timestamp: September 04, 2023, 10:12:04 am
content: Quote from: xavier60 on September 04, 2023, 03:34:40 amYou are right about the required sensitivity when poking for shorts on GP and tracks. In its' voltage drop measurement mode, theBug Houndfeatures ±50 and ±500µV FS.Quote from: Rooster Cogburn on September 03, 2023, 01:08:55 amYet I haven't tested with sputtered resin, but I would say that it has a higher vaporization temp. than IPA and also raises some smoke which eases to locate the frying parts. Might be of good help when working without an IR cam.And what aboutthese IR camsmounted on a stand ? Realy fast update rate and decent resolution (256 x 192 pixels). Certainly not as good as a genuineTeledyne/FLIR IR camwith patented dual spectrum MSX mode (which means contour extraction on visible image, and not an unusable video merge), but 10 X cheaper and with significant faster update rate.

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2023, 05:16:57 pm
content: One thing that's worth remembering is that IR visibility is inversely proportional to the 'quality' of the short. If a capacitor has gone resistive, it will light up like a beacon with reasonable current, one that has gone dead short, or it's something like a solder bridge, it won't have significant voltage across it and so will hardly dissipate. In these situations, you will need to look for collateral heating, track heating, regulator IC etc. and then play Sherlock Holmes from there.I gess what I'm saying, and finding actually, is that best case, a thermal camera can zero you in really quickly but you need be equipped to perform the voltage drop method too. You're going to need it at some point.