Best cheap multimeter that has a good Min/Max function?  - Page 1
Forum section: electronics / testgear

author: Studly
author_rank: Newbie
timestamp: February 11, 2021, 10:41:18 pm
content: I'm the opposite of an electronics wiz, so need the help of the people in this forum, please. I'm looking for the cheapest multimeter that has a good Min/Max feature. Basically, I just want it to regularly load test my vehicles' 12v batteries while cranking the starter with the Min/Max button activated, just like this video explains:.I was looking at the Astro AI 4,000 count DMM that is only $23 on Amazon (https://amazon.com/AstroAI-Multimeter-Resistance-Transistors-Temperature/dp/B07FDBW1PT) because it has a Min/Max function, but it's specs say it only samples 2 times per second. I'm not clear if that just means its display samples at 2X per second or if the Min/Max feature will sample the voltage only 2X per second. Obviously, I'd want the Min/Max feature to sample as many times per second as possible so I know how low the voltage gets when I'm cranking my starter on my car.I've also been looking at a Uni-T UT139C DMM, which is quite a bit more expensive ($40 on ebay, shipping from China) and has more features than I'd probably use, but it seems to be better built and was wondering if that DMM's Min/Max feature would perform better and be worth the extra money?Any other recommendations on a low price DMM (preferably auto ranging) with a Min/Max feature would be greatly appreciated! I don't really understand how to interpret all the specs for DMMs, so please don't get too technical when explaining why a certain DMM is a good one for my case.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 12, 2021, 04:47:26 am
content: If all you are interested in is checking 12V car batteries it's easier to just apply your own load with a "toaster tester" than it is to use the starter and try to catch the minimum with a DMM.For examplehttps://www.harborfreight.com/100a-612v-battery-load-tester-61747.html?_br_psugg_q=battery+tester,if you want to compare to the starter's load, just watch the needle while a helper starts the engine.

author: Studly
author_rank: Newbie
timestamp: February 12, 2021, 04:00:20 pm
content: Quote from: BrokenYugo on February 12, 2021, 04:47:26 amThanks for the reply. Actually, I was thinking of buying that Harbor Freight tester originally, but then got some feedback from car people that the 100 amp load it provides isn't near what a starter draws. But I didn't think of using that while starting the car and checking to see how low it would go ... good idea! I'm just wondering, though, if the needle would drop so fast on that HF tester that it would be difficult to tell how low that it goes when the starter is cranking and drawing the peak amt of amps? Have you tried that technique with a tester like that?

author: bdunham7
author_rank: Super Contributor
timestamp: February 12, 2021, 04:29:52 pm
content: I've done this more than once and the only tool that gives accurate results is a scope, in my case a Fluke 98 Scopemeter. I've compared to even DMMs that were auto-specific and I haven't seen one with a min-max that was fast enough to catch the dips that a scope can. Watching an analog meter can give you some idea, but it won't be particularly precise. Then the question is, how precise do you need to be? If the answer is that you don't need much precision and you want it cheap, the HF analog meter idea isn't bad. Some meter movements are faster than others, often cheap ones actually are undamped and will be quicker. If you do need some precision, a cheap battery operated scope is the way to go. That or a Picoscope if you don't mind using a laptop with it.If your only goal really is to track your battery performance, then the HF tester makes sense. The peak starter draw will vary quite a bit depending on temperature and random chance.

author: BrokenYugo
author_rank: Super Contributor
timestamp: February 12, 2021, 08:19:48 pm
content: I didn't comment on it because I've never tried but I did suspect min/max on a meter would struggle, the min isn't going to be flat, it's lumpy as the engine comes over each compression stroke.I'm not familiar with the exact tester in question, but will hazard a guess the meter movement is sensitive enough to show the dip if there is enough of a dip to worry about in the first place.Because you can hold the load with a toaster tester for as long as you dare the toaster tester can evaluate the battery more effectively, a multimeter or even a scope won't show a weak cell as easily as holding the load switch down for 20 seconds or so and looking for the sudden 2V voltage drop. Though really none of this matters unless you're a real penny pincher, car flipper, or diy power bank enthusiast with a bench power supply or dumb charger to balance/desulphate the iffy battery (or as I call it cooking the crap out of them, a somewhat dangerous process) in question to get maybe another year out of it.The cheapest and most practical test, in my opinion, is to pay attention to the cadence of the cranking, and throw a new one at it (first investigating the connections and charging system function) when it sounds slow on cool/cold mornings. Don't forget to slather the posts, area where the posts go through the case, and terminals with grease (any will do, I use wheel bearing) shove the terminals down as far as they'll go on the post (it's a taper fit) and tighten the terminal only until the bolt is snug and terminal grabs the post snugly, replace terminals if this cannot be achieved, don't lose the hold down hardware, and repair/replace anything missing/broken. I find half-assed installation is more of a reliability problem than the battery itself. If the car sits more than a week or two between 20+ min trips disconnect the battery or add a quality maintainer/float charger.All that said, I do not mean to discourage multimeter ownership in any way, I just don't think its a good tool for this job, with automotive in general I rarely pull one out unless I'm dealing with sensors (checking reference voltages and such), want to see voltage drop on a suspect cable, or need to check parasitic draws, any DMM will do for that, I know Aneng 8008 is liked for such low voltage work, but even the formerly free Hazard Fraught meter will do. For 12 V power circuits I mostly just use a mid price harbor freight test light.

author: Studly
author_rank: Newbie
timestamp: February 12, 2021, 08:59:50 pm
content: All great helpful information provided. Thanks!

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: February 13, 2021, 04:42:13 am
content: The purpose of such test is to evaluate whether a particular battery is good/adequately charged to start a particular car under a particular condition. We are not looking for glitches in a digital signal and a high sample rate is not required, any voltage drop is gradual enough to be picked up by a respectable DMM with a MIN function.Such test takes the particular car, engine, current draw outside of the starter, and ambient temperature into consideration, as the current draw to start a 4 cylinder car is vastly different from a big diesel, toaster tester focus only on the battery, and not the entire system as a whole. Hence it is becoming a popular option vs. the decades old load tester. Both test methods have their merits, and answer a particular set of questions. Most of the new battery analyzers have moved away from the old load testers and fits in your pocket, it not only monitors starting conditions, but also charging circuits. However the old tester is perhaps still the cheapest to buy, especially if you shop at HF.Back to the original question, I use my Fluke 179 and 375FC to measure min starting voltage and peak current draw. They both give reliable data on the battery health and starter current draw, but they don't answer the question of which cheap DMM can perform such function. I would suggest using Joe Smith's testing as a base to pick a safe DMM, and find one that has a MIN MAX function that fits your budget. That way, you are getting something that you can safely use around your home, in addition to checking your car battery health.

author: Microcheap
author_rank: Frequent Contributor
timestamp: February 13, 2021, 06:37:42 pm
content: If you want just a cheap meter, the Vici VC97A has the Min/Max function. Out of curiosity, I tried it in my car and it can do the test just fine.I don't know how it would compare against the Astro AI. The build quality of the Vici looks and feel a bit cheap but it works great and it has a big display with a good contrast, making it very easy to read.I also have the UT139C and it is definitely a better product, if you can spend a bit more, I think it will worth the investment. If not, the VC97A can do the job and, to be honest, I like it and I use it more often than the others DMM that I own.

author: Studly
author_rank: Newbie
timestamp: February 13, 2021, 07:43:05 pm
content: Quote from: NoisyBoy on February 13, 2021, 04:42:13 amThanks for the info ... yeah the guy in the video used a Fluke as well. Unfortunately, that's out of my budget. :-( But helpful info here!

author: Studly
author_rank: Newbie
timestamp: February 13, 2021, 07:50:14 pm
content: Quote from: Microcheap on February 13, 2021, 06:37:42 pmGood to know! Will check out the Vici you recommended. Was going to buy the Uni-T UT139C for sure, but I bought one as a gift for someone last year for $32 on Ebay, and now they are selling for $40 on ebay. One of the sellers I contacted said there was a price increase from Uni-T since the last one I bought. Another posting I saw said the UT139C with the higher price also had recent manufacturer improvements from the old one. Is it a good value for $40? I have a few basic multimeters that I own, but that Uni-T would have many extra features, although not sure how many I'd use. Anyway, thanks for the helpful reply!

author: wizard69
author_rank: Super Contributor
timestamp: February 14, 2021, 09:11:25 am
content: Sadly I don't think you are going to get a DMM that is consistent enough to be useful here. I don't use a multimeter for automotive work much but do use such in industry and frankly the Min/Max functions are of limited usefulness. The concept sounds good and maybe useful on slow moving variables but on fast moving glitches they simply do not sample fast enough.The other problem is testing with the starter is not reliable in the sense that you are not presenting a repeatable load. Starters, engines, oil and temperature vary widely so you can't make the assumption that what is bad on one vehicle is also bad on another.Your best bet for battery testing is one of the dedicated load testing computerized "things" that are available. These dedicated battery testers can be programmed for just about any battery type found in a car and depending on the model may offer more than one test type.Sadly I'm not a big fan of analog meters in the garage, they invariably get damaged in some manner. So I would discount them unless you have amazing storage and handling skills.Now hear is another reality from somebody that has lived in the great white north forever. You really don't need a battery tester per say. Simply replace the battery every 4 years or quicker and practice good maintenance of the battery wiring. Over the years I've had more issue with connections than batteries themselves.So that being said you would be far better off buying a good DMM that can handle the more general maintenance issues on an automobile. If it has Min/Max all the better, just don't expect it to be the absolute solution to debugging battery issues.By the way a battery test without a DMM's Min/Max function is possible. That is measure battery performance twice a year in a repeatable manner, keep a record and watch for changes. You would want to disable ignition and take a cranking reading at a precise time after cranking starts. At some point in the cranking process the voltage should be steady state for a short time. Take your voltage reading then. We are talking only a couple of seconds here, you don't want to fry the starter testing the battery.