Multimeters: How cheap is too cheap? - Page 1
Forum section: electronics / beginners

author: Emyr
author_rank: Contributor
timestamp: March 29, 2010, 01:04:17 pm
content: A £170 Fluke 80-series is way beyond what I can justify spending as a true beginner in electronics; Most of what I've made so far involved attaching a few sensors and an LCD to an Arduino (RFID coming soon...), and my soldering is still a bit shoddy.How useful do you think the £25 Amprobe DM7C would be to a beginner? Should I exchange some of the quality for extra functions?http://www.amprobe.eu/en_GB/showproduct/139/DM7C/

author: chemicaloliver
author_rank: Contributor
timestamp: March 29, 2010, 05:58:26 pm
content: This is a good question, I would say yes for what you suggest there is no need for an expensive meter, what you get with an expensive meter is confidence, accuracy and safety. At arduino power levels safety is not really an issue and it doesn't matter so much if your measurements aren't 100% accurate. If you're doing anything with mains you'd want to get a good meter however for low power stuff a cheaper meter will be ok.I started with a ~£40 multimeter from maplin (http://www.maplin.co.uk/Module.aspx?ModuleNo=46381) and I never had any issues despite it basically being a bit rubbish compared to expensive meters.I now have a ~£200 Agilent meter and the difference is amazing in terms of feel and accuracy, but I wouldn't say the cheaper meter held me back, it's just that I now have more money and like nice things.So in short I think the meter you suggest would be fine, although it seems to only measure up to 200mA which could be limiting. I would look for something with a bit more DC current range but I wouldn't say there is a need to pay a huge amount of money.

author: EEVblog
author_rank: Unknown
timestamp: March 29, 2010, 08:09:24 pm
content: I concur with Oliver.A cheap meter is fine for general use, but I'd go for something with better features than the DM7C. The 1Mohm input impedance, manual ranging, and no mV, 200ohm, Amps or uA ranges is just far too limiting. Most other cheap no-name meters don't have these limitations.Dave.

author: EEVblog
author_rank: Unknown
timestamp: March 30, 2010, 06:25:09 am
content: The Amprobe 240 is much better equipped and is only around UK$31http://www.amazon.co.uk/AMPROBE-FLUKE-COMPACT-DIGITAL-MULTIMETER/dp/B0024VDE1UDoes Capacitance, 10A, uA, autoranges, min/max, temp etc.Dave.

author: EEVblog
author_rank: Unknown
timestamp: April 01, 2010, 10:37:43 pm
content: Quote from: Joy at MCS on April 01, 2010, 02:16:43 pmAmprobe are owned by Fluke (formally Meterman). Designed and built in Asia, but tested and certified at Fluke USA. They are the #1 multimeter brand in the US apart from Fluke, if you believe Fluke that is!Dave.

author: jklasdf
author_rank: Regular Contributor
timestamp: April 02, 2010, 05:05:08 am
content: I would recommend against the am-240:In the DC volts range, it reads ~300mV even when not connected to anything. This might be acceptable in the AC volts range (actually a little high even for AC) because of interference from the mains, but I have never seen this happen in the DC volts range -- even on the cheapest multimeters. Shorting the probes together, or connecting the multimeter to an actual DC source less than 300mV does give the right reading.The continuity test takes a long time to register, and it doesn't help that the probes included don't make good contact. (Even with quality probes, it still takes a long time before beeping.) Also the probe tips are not very sharp. Also, the frequency counter picks up the 60hz mains hum which is kind of annoying, but still understandable.Since you were looking at the dm7c, I would recommend the slightly more expensive dm9c, which corrects most of the problems mentioned by Dave. In this price range, I think it's a better idea to buy a good meter with just the basic features, instead of a really cheaply made one with too many features.

author: dds
author_rank: Contributor
timestamp: April 02, 2010, 12:20:08 pm
content: What about used FLUKE 25? It sells on ebay for 21 quid + postage, military version built like tankhttp://www.surplustest.co.uk/product.php?id=12

author: dds
author_rank: Contributor
timestamp: April 02, 2010, 12:27:24 pm
content: Quote from: EEVblog on March 30, 2010, 06:25:09 amI think capacitance meter on DMM s almost useless, it's better to buy dedicated ESR meter. Is This correct?

author: EEVblog
author_rank: Unknown
timestamp: April 02, 2010, 10:33:11 pm
content: Quote from: dds on April 02, 2010, 12:27:24 pmNot really, they usually do a reasonable job. If you need good accuracy, selectable frequency etc, get a proper LCR meter, but the cap range on most multimeters is more than good enough for the purpose of identifying and comparing caps etc.Dave.

author: DJPhil
author_rank: Frequent Contributor
timestamp: April 02, 2010, 10:37:31 pm
content: Quote from: dds on April 02, 2010, 12:27:24 pmIt really depends on your needs. I understand ESR meters to be most often used to check the condition of a capacitor that may be aging ungracefully. When building with new parts you'll likely be using new low-ESR caps to begin with. You're probably more interested in their value, especially if you're working with mystery SMD caps that are usually unmarked (which bugs me). Match up the accuracy specs of the meter versus the tolerance of the sort of caps you often deal with, and you might be surprised. Off the top of my head (I've a horrid memory) electrolytic caps are the most horrid with a common tolerance of +20% to -5% of their labeled value, and other types not fairing much better than +/- 5% without special investment. I use mine often to check that the caps I'm using are at least in the ballpark, as I use a lot of salvaged parts. Most LC meters will measure smaller values than a multimeter (<1nF) and it can be difficult to find a device capable of measuring higher values (>1KuF), though it's not often necessary.In short, it's a convenience feature that has some value for most hobbyists, especially if you have nothing else. I would suggest that you buy or build if you need high precision and wide range. There's awhole lotofprojects out therethat result in good LC meters, and the ability to measure inductance is quite handy as well. There's alsoat least one diy ESR meterif you're troubleshooting or repairing older stuff. If you're just getting started, it's useful and worth your consideration until you can build something better, and doing so will teach you a great deal!Hope that helps

author: ArtemisGoldfish
author_rank: Regular Contributor
timestamp: April 08, 2010, 04:34:08 am
content: Quote from: dds on April 02, 2010, 12:27:24 pmErrr, the capacitance meter on DMMs IS pretty much useless, but an ESR meter isn't quite a direct comparison, since capacitance and ESR are separate values. Then again, an ESR meter is probably more useful (though I'm just saying that because I really need one to find the bad caps in my 80's analog scope.)Anyways, just for simple hobbyist-type usage, the average cheap DMM is *probably* fine. I use a little Radio Shack generic DMM with a fairly standard feature set (useless capacitance meter, ohms, diode forward voltage drop, uA/mA/A, continuity) and it works fairly well for what I use it for. Paid about 25USD for it.

author: Simon
author_rank: Unknown
timestamp: April 10, 2010, 05:22:35 pm
content: I've just bought the amprobe AM220, it seems to be a decent unit for the price although I'd prefer something a bit more robust but at the end of the day you get what you pay for. I think the no name meters on ebay are well overpriced considring you are taking a chance on a unit that costs as much as an Amprobe one wil almost as good (on paper) specs and you have some assurance that it was made under the glance of a company with a reputation

author: Ronnie
author_rank: Regular Contributor
timestamp: June 24, 2011, 03:02:56 am
content: This generic DMM cost less than US$3 (equivalent to Philippine Pesos 120)http://www.cdrking.com/?mod=products&type=view&sid=2849&main=92

author: ejeffrey
author_rank: Super Contributor
timestamp: June 24, 2011, 08:16:53 am
content: Some multimeter capacitance ranges are useful, others are not. For instance, the cheaper Flukes (170 series and 110 series) have 1 nF resolution. That is not really useful for electronics use. I guess they are designed for electricians measuring motor start capacitors or power factor correction capacitors. On the other hand, most if not all of the meters in Dave's shootouts have 10 pF or 1 pF resolution (with an accuracy of 10-20 pF in the ones I looked at). This is not a replacement for a high precision cap meter or LCR meter, but it is totally sufficient for a lot of electronics applications.

author: Psi
author_rank: Super Contributor
timestamp: June 24, 2011, 10:26:56 am
content: I use the capacitance range on my DMM's quite often, and i have an actual LCR meter.Sometimes you don't need accuracy. You just want some idea of what value a unmarked capacitor is.And it's easier to just switch the DMM your already using to capacitance range than it is to go get the LCR meter out of its case.

author: Zero999
author_rank: Super Contributor
timestamp: June 24, 2011, 08:42:17 pm
content: I've heard about lots of problems with cheap meters exploding when subject to a surge on the mains which is true when used in an industrial situation but less likely on domestic mains.Although I wouldn't recommend using a cheap meter to measure mains circuits directly, it's not so dangerous if the circuit is connected to an isolation transformer which you should be using anyway for building and testing mains appliances.An isolation transformer separates the mains supply from earth so even if there's a spike it will only occur between the live and neutral connections, not earth. It also increases the impedance of the supply meaning that the short circuit current is reduced so there's less chance of your meter blowing up, if the crappy fuse can't take the short circuit current.I have a small 100VA isolation transformer which is fine for the odd mains project which is not already run from a mains transformer.

author: tsmz
author_rank: Contributor
timestamp: June 24, 2011, 09:43:48 pm
content: I'll be really blasphemous and say that there's (almost) nothing too cheap for an Arduino.Even the crappiest cheapest 5-$/EUR/GBP meters will be perfectly fine, safe and capable for Arduino stuff. But, and that is a very important point to make, you're absolutely forbidden to use them foranythingelse.When working with the Arduino, there's a nice safety feature built into the board: The self-resetting fuse. So even if you're running your Arduino board from a dodgy non-current-limited power supply, the Arduino will not draw excessive amounts of current; you'll probably get 500 mA from the arduino board, but that's about it. So even crappy meters shouldn't be a hazard unless you don't know what you're doing and leave the thing running shorted for days. However, it's important to only use this multimeter for the Arduino and not for anything else. Accuracy is not a big problem, because most of the time, you'll be measuring ballpark voltages and maybe small currents. Really, a multimeter for the Arduino can in theory be as simple as a panel meter with a selection switch, what is basically your el-cheapo multimeter.Do I recommend this? Not really. Cheap multimeters aren't cheap for no reason; it's okay to have one around, but you can't use them for anything that's not inherently safe (the Arduino is), so I don't see the point if you do want to spend some money. The real cheapies suffer from horrible haptics and small displays as well, which is of much greater concern than safety when it comes to the Arduino. So while the real cheap ones do work, they're quite a pain to use, so I recommend getting at least a "decent" cheap one with a big display. Depending on availability and prices, you're then better off getting an affordably priced meter like the already suggested Amprobe units.

author: Bored@Work
author_rank: Super Contributor
timestamp: June 24, 2011, 10:20:43 pm
content: The issue with cheap meters is they don't age to perfection. They remain unsafe and are just an accident waiting to happen.Someday, maybe a long time in the future, you might forget they are unsafe or chose to ignore what you know and use them on mains. Or it gets into someones hands who doesn't even know the junk is not save and believes the numbers printed on the case.Therefore it isnotokay to have one around. It is not okay to give money to the lying pieces of shit who manufacture and sell them in total disregard for your and other person's lifes.

author: westfw
author_rank: Super Contributor
timestamp: June 24, 2011, 10:46:08 pm
content: I have several of the "$3" meters, and I think they're great. I don't think I've ever used them on even 110V domestic power, where they are no doubt nearly as dangerous as exposing contacts for them to touch, or driving to work. I've never been anywhere near the sort of industrial power that causes them to explode in spectacular fashion as shown on youtube, and I don't expect to be. I need the safety features of an expensive meter to measure my arduino, the way I need "intrinsically safe" lighting and fans in my bathroom...

author: tsmz
author_rank: Contributor
timestamp: June 24, 2011, 11:10:21 pm
content: Of course, you never know who uses a multimeter for which purpose, so if there's the chance of people using the multimeter for things it was not designed for, you should get one with at least basic safety features, no questions asked.However, for a device like the Arduino, which is quite safe already, cheap meters can be used. It might be best to replace the test leads with small clips or hooks so there will even be less mistaking that this will be a low-voltage, low-power measurment device.I don't think the cheap multimeters are great, because they aren't, but specifically for the Arduino, there is no "too cheap," except if the multimeter will fall to pieces as soon as it's taken out of its packaging. I think they're quite painful to use due to their puny display, but even the cheapest multimeters are suitable to use for the Arduino. If my multimeter mysteriously broke down today and everything I could get was a cheap garbage meter, and I urgently needed to measure stuff on the Arduino, I wouldn't hesitate buying one. They're just barely suitable for extremely ballpark (too cold to touch, might be safe to touch, too hot to touch) temperature measurements (most of them come with a half-assed thermocouple), so they still are of some use as soon as your decent meter is working again.I do think intrinsically safe equipment is quite worthwile, even the light fixtures in a bathroom. If the Arduino didn't have the relatively low current limitation, I also wouldn't recommend a cheap multimeter for it, because it can get quite nasty when measuring "voltage" with the leads plugged into the current terminals for even medium currents and crappy meters. With the Arduino's intrinsically safe current limit, this will probably just damage or destroy the meter (which is one of the reasons why it's a bad idea to buy an ultra-cheap meter), but that's about it.

author: Zero999
author_rank: Super Contributor
timestamp: June 25, 2011, 09:03:22 am
content: Don't forget, it's often the current which is more of a danger than the voltage because it can cause burns and fire, even if the voltage is too low to shock or kill.The worst kind of cheap meters are those without a fuse on the current setting. This isn't too hazardous for current limited power supplies such as small batteries (9V AA ect.), mains adaptors or an Arduino board but they're very dangerous for high current sources such as car or Li-ion batteries, even more so than a mains appliance with a low current fuse (<5A). If you accidentally connect the meter across the terminals of a large battery when it's set to read current, the meter, the leads or the battery will meltdown and could catch fire.Even fused meters aren't safe because the fuse often has a poor breaking capacity (its ability to safely interrupt the current). If the breaking capacity of a fuse is exceeded, it might fail to open the circuit which could result in a fire or explosion. For example using a meter with a crappy glass fuse with a breaking capacity of only 35A on a 12V automotive circuit is very dangerous.

author: orbiter
author_rank: Frequent Contributor
timestamp: June 25, 2011, 10:28:18 am
content: I'm sure the Amprobe would be fine, however the current range as already mentioned could be a bit of a restriction. I know it's a little more expensive at £41, but have a look a theExtech EX330It's a great little meter.

author: saturation
author_rank: Super Contributor
timestamp: June 25, 2011, 11:48:42 am
content: Many of the Harbor Freight or similarly priced cheapo DMMs are often much cheaper than a LCD panel meter, and can be easier to mod than to build support circuitry from scratch.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: June 25, 2011, 04:15:23 pm
content: Quote from: saturation on June 25, 2011, 11:48:42 amBe aware that these often have floating-ground supplies, i.e. input ground isn't connected to battery but to a midpoint, which can make them a bit of a pain to power.

author: Unknown
author_rank: Unknown
timestamp: June 25, 2011, 04:58:41 pm
content: Many digital panel meters also need a power supply floating relative to the input signal.

author: Zero999
author_rank: Super Contributor
timestamp: June 25, 2011, 06:18:01 pm
content: At least panel meters normally have differential inputs which will work fine as long as the signal is within the common mode range but this isn't always the case with DVMs which may have one input floating.

author: Unknown
author_rank: Unknown
timestamp: June 25, 2011, 06:26:27 pm
content: Plenty of panel meters position the negative input something like one diode drop above power supply ground.

author: Armin_Balija
author_rank: Regular Contributor
timestamp: June 27, 2011, 07:03:24 pm
content: Quote from: BoredAtWork on June 24, 2011, 10:20:43 pmThumbs up for that. I like saving money just as much as the next guy, but I save my money on food and things I can get away with. I only buy quality scopes and meters because you never know when your life might be on the line when using cheap and unreliable test equipment.

author: ivan747
author_rank: Super Contributor
timestamp: July 02, 2011, 01:53:48 am
content: Quote from: Ronnie on June 24, 2011, 03:02:56 amI've heard of cheap meters, but that is INSANE! Ah, by the way,I have one of those and the milliamps range is completely fake!It doesn't do any measurement at all no matter which socket I use.100th post, now I am a full member, yay!

author: Bored@Work
author_rank: Super Contributor
timestamp: July 02, 2011, 08:13:50 am
content: Quote from: ivan747 on July 02, 2011, 01:53:48 amYou blew the fuse.

author: ivan747
author_rank: Super Contributor
timestamp: July 03, 2011, 06:42:34 pm
content: Quote from: BoredAtWork on July 02, 2011, 08:13:50 amOh cr*p, I did! What an idiot.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 03, 2011, 06:52:46 pm
content: Quote from: ivan747 on July 03, 2011, 06:42:34 pmPlease people take a big breathNo one is an idiot because he burned one 0.3A fuse !!Most small factor DMM they have 200mA ranges ... protected by 0.3A fuses.It is very easy to kill this fuse, even if you do measurements on battery powered toys.This is why you get an small box of 10 fuses, so to have plenty as spare.

author: westfw
author_rank: Super Contributor
timestamp: July 06, 2011, 02:33:42 am
content: But that's why these meters are dangerous, right? If you had been measuring a 480V multi-kiloamp circuit on the 10A setting (accidentally, or something), there wouldn't have been any fuse at all (much less the fancy safety fuse that ought to be there), and the whole thing would have turned into an "exploding wire" phenomena that would have killed you! (um... Right.)

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: July 06, 2011, 12:21:29 pm
content: I fear more the dangerous users,than a small device, called as DMM.The dangerous user is able even to destroy a car that worth's 40.000$ ,even if the poor car, had past all the safety tests.