Multimeter with capacitance vs LCR meter? - Page 1
Forum section: electronics / beginners

author: TheBorg
author_rank: Frequent Contributor
timestamp: November 21, 2013, 04:19:06 am
content: I am a beginner in the field of circuit design and repair, and have gotten along for the past couple years on a Harbor Freight (el cheapo brand) multimeter. I have developed an interest in computer motherboard repair, and I doubt most of my current equipment will really do the job any more (I need more precise measurement). One of the problems I have come across is testing SMD capacitors on motherboards to see if they are good or not. To make sure the cap is giving me the right value (and also to reverse-engineer the schematic), I need something to measure capacitance. Doing some research has landed me with pretty much two options (if there are more let me know). The first is to get a multimeter with a capacitance measurement function. However, these seem to be hailed as inaccurate and should not be used. The other option is to get a dedicated LCR meter and use that. I need help choosing between the two.Basically what I really need to test are the values of capacitors ranging from 0-10uF in capacity, these range in size but are generally 0603 and larger. Accuracy is needed, but only pretty much to a one decimal accuracy (e.g 1.1 uF). My budget is only like $50 USD. Is it even possible to get a decent meter for that price? I am fine trolling eBay for a few months to try and score a Fluke meter or some other high brand if that would be recommended. Or am I just being an idiot?

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 21, 2013, 04:39:43 am
content: Do you intend to measure these capacitors in circuit? I mean without desoldering them? If so accuracy is not an issue, because you can't accurately measure a capacitor in circuit without considering the bits connected to it. In fact, I would say 9.5 or 9.9 times out of ten you cannot measure a capacitor in circuit at all.The vast majority of capacitors on a motherboard are used for local power supply decoupling, which is to say they act as little batteries which are physically close to a fast chip, providing it with power until the main power from the power supply "gets there". Which is to say, the vast majority of the capacitors on a motherboard are connected together in parallel. There's no way of measuring one of these thousands of capacitors connected in parallel without removing it from the circuit.That said, it seems to me that the vast majority of capacitor failures on motherboards are not with the little SMD decoupling capacitors, but rather with the bulk electrolytics. And the way those tend to fail doesn't really show up very well on a capacitance measurement, but rather an ESR measurement.One thing to look out for with multimeter capacitances ranges is that they're often very limited. I find the capacitances I'm most interested in measuring is frequently outside the range of my multimeters.Let me know if I'm on the wrong track here and you're already past this stuff.

author: Shock
author_rank: Super Contributor
timestamp: November 21, 2013, 04:44:57 am
content: I have just recently replied to a post on a few points on cap testing- read this thread.For maximum flexibility an equivalent series resistance (ESR) meter that shows capacitance is what your after.You can get a Chinese made multifunction ESR meter online shipped for under $20. Same in a nice enclosure for $30.If your looking for more I'd recommend a DER EE DE-5000 for $100 which has kelvin (4 wire) testing.For in circuit testing the Peak Atlas for $160 is the way to go. But read the caveats and follow all the links and check if you like the specs.

author: nanofrog
author_rank: Super Contributor
timestamp: November 21, 2013, 04:51:19 am
content: I would say an LCR would be the right way to go (offers more than capacitance testing, such as ESR; capacitance alone isn't really enough to determine if a cap is good or bad).As per price and models, there are a few reviews of LCR's in here, but I think you may be a bit hard pressed to find one that works well enough in your price range (there are inexpensive units on eBay, but I'm not familiar with them).TheAtlas ESR70might be worth a look IMHO, but it's nearly 3x your budget (~$137USD shipped on eBay). Few others too, such as a UniT model, IET 5000 (IIRC), and others. Don't recall any of them in the $50USD realm though.

author: Wytnucls
author_rank: Super Contributor
timestamp: November 21, 2013, 05:00:49 am
content: Here is a review of one LCR meter I own. Not too bad considering the cheap price. Low voltage for in circuit testing, but you need to make sure no caps are wired in parallel. Limited range and no ESR, but you're only interested in capacitance value, if I understand correctly.Measurement frequency fixed at 150 Hz.https://www.eevblog.com/forum/testgear/uyigao-ua4070l-lcr-meter-review-and-tear-down/msg191838/#msg191838

author: TheBorg
author_rank: Frequent Contributor
timestamp: November 21, 2013, 05:08:55 am
content: Ok, seems I need to do a lot more research. Better now than out $50 with an unusable tool thoughI don't know about desoldering the caps. It's a possibility I can remove them, but I would rather not. The process I usually would do is to find a problem with a chip, and try to work my way down the line to see what specific parts have gone bad. Naturally I wouldn't want to desolder them all, but to get an accurate reading I suppose that's the only way to get a good reading. I would like to be able to measure whether the cap is good or bad, as well as capacitance. Out of those two I would choose good or bad if I could only get one tool. That Atlas has been recommended twice though... I might be able to sway that later on but probably not until next year.Ill do some research after school this week and try to have a near intelligent conversation... And please, if you think I am going about this the wrong way let me know. I'd be happy to learn from any criticism you give.Got a new post message... Thanks wytnucls, ill take a peek at that. Usually ill have the schematic of an area I nee to work on, but finding out which parts are which is the hard part.

author: true
author_rank: Frequent Contributor
timestamp: November 21, 2013, 05:16:17 am
content: I second the DE-5000. Better to get a great tool that will last than to get a shit tool that won't. Unless that shit tool is the $3 HF meters, I used those for a while too before my collection got built upEspecially since the price went down with the Japanese sellers now on the market.Do you plan to repair more than one or two boards? Do you really think the caps are a problem?(happy owner of two DE-5000 LCR meters)

author: TheBorg
author_rank: Frequent Contributor
timestamp: November 21, 2013, 05:23:35 am
content: Yeah they are the $3 HF meters. Usually if you buy stuff during a sale though or have a coupon they'll give one to you free. I have like 5 or so now. The meters are great but the tips are crap lol...I'm planning on doing macbook motherboard repair, partly as a hobby but I eventually want to see if I can get through college doing it. Plus I'm thinking about an EE major so hopefully the skills and knowledge I get now will help. So yeah, I plan on doing more than a few boards. And keeping the tools until I can afford better ones or they die on meAs or the caps I don't know if they would be the cause but I would like to be able to rule them out at least for the cause of a break in the circuit or a short from water damage. Usually I doubt they would be the problem but I've attempted to repair some models and I just never really could tell if a cap was bad or just giving a funny reading.