Trying to choose a moderately decent meter... help! - Page 1
Forum section: electronics / testgear

author: CharlieWorton
author_rank: Regular Contributor
timestamp: November 30, 2017, 06:44:13 am
content: I've spent the last 3 hours going around in circles... my brain is tired. Here's what I'm looking for:Price $100 CAD ($78USD) or less (will spend somewhat more, but only with great motivation)20,000 count or better meterback lightrelative measurement buttondata line out to PCtemperature probeTrue RMSI wanted a nice, general high precision meter that I could also use to log temperature changes on a heated plate. Hence the need for the temp measurement and data out.The Uni-T UT61E almost works, but doesn't have a back light or temp probe.The Uni-T UT139C almost works, but is a 6000 count meter with no data line out.I think I've looked at a hundred different meters tonight. Totally fried.The UT61E has such a small, crowded display. How could they not include a back light? What were they thinking? Or smoking?Maybe I could hook a thermistor up to a UT61E and use those readings, then correct them into actual temps using a calibration table. What a kludge.And while I'm here... please sort me out on this one:UT61E Resistance Best Accuracy 0.5% +10So, given a 100 ohm resistor, the meter might read 99.5 to 100.5 ohms... but what's that +10 thing? Just toss an extra 10 ohms into the soup? Please educate me...Wow. I need beer. >Charlie

author: beanflying
author_rank: Super Contributor
timestamp: November 30, 2017, 07:02:50 am
content: For temp logging Arduino, Maxim based module and a 3 or 4 wire RTD for under $20 is an option. Chinese based Multimeter logging software generally SUCKSI have been using two Victor 86's for years on my coffee roasting with K type thermocouples but non meter freeware for logging. Roastlogger or Artisan. Not sure what other meters it supports (never really looked) but logs are saved in csv files against time so might suit your application.Backlight - Get a torch

author: HalFET
author_rank: Frequent Contributor
timestamp: November 30, 2017, 07:04:23 am
content: I've never seen the need for a backlight on the u61e in a well lit lab to be honest about it.But the rating of x% + y is split up due to the source of the error. The y is the number of counts error. E.g. a 20000 meter on a 200 Ohm range would have a resolution of 10 mOhm in the best case, but if it makes a +/- 8 count error that means your measurement is uncertain in a 160 mOhm range. The reason for the separation is that this is an ADC error, quantization noise basically. The percentual error usually comes from the rest of the circuit and calibration drift.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 30, 2017, 07:09:00 am
content: I have never once said "Geeze, I really wish this had a backlight". Who probes in the dark?Accuracy can be important, but very often precision is all you really need.

author: Nusa
author_rank: Super Contributor
timestamp: November 30, 2017, 07:14:27 am
content: Google "ut61e backlight mod" if it's actually that important to you. There are quite a few variations on the theme out there.Trying to make one meter do every job is not necessarily as good as two or three meters that can do every job between them. Mainly because the one meter can only do one job at a time.

author: beanflying
author_rank: Super Contributor
timestamp: November 30, 2017, 07:15:09 am
content: Quote from: Paul Moir on November 30, 2017, 07:09:00 amMains AC dark room No problem

author: HalFET
author_rank: Frequent Contributor
timestamp: November 30, 2017, 07:19:01 am
content: Quote from: beanflying on November 30, 2017, 07:15:09 amProbing mains with a 61E is suicide.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: November 30, 2017, 08:19:03 am
content: I'm just going to elaborate on the "precision is sometimes is all you need" comment by way of an example. A coworker recently purchased a UT61E and was curious about how accurate it was. I lent him my 2.5V reference and he checked it and indeed it was pretty decent. But since the UT61E is a 22000 count meter, it ranged into the 22v range when checking the reference, which robbed him a digit. He was able to use a resistor divider to get the reference down below 2.2v, and measure the divider ratio using his UT61E.Do you have reason to care about CAT ratings?

author: beanflying
author_rank: Super Contributor
timestamp: November 30, 2017, 08:30:40 am
content: Within the bounds of personal hobby user safety as a minimum we should ALL be concerned about CAT safety even if just for the sakes of our families.

author: CharlieWorton
author_rank: Regular Contributor
timestamp: November 30, 2017, 11:23:18 am
content: Thanks, everybody - I really appreciate your feedback.Since my original post I did indeed discover that many have created ingenious lighting solutions, including one right here on this blog:https://www.eevblog.com/forum/testgear/uni-t-ut61e-backlight-mod-with-touch-sensor-(tutorial)/I'll solve the temp logging problem separately.And then I found the meter on sale for $64 Canadian - through Amazon, no less - with no GST owing and free rapid shipping, so I grabbed it. The same meter through China is $75 with a 3 month wait. Here's the Amazon link:https://www.amazon.ca/dp/B007THZMWI/ref=pe_3034960_233709270_TE_itemShould have it in a couple days.Re backlight usefulness... I dunno, maybe you all have eagle eyes. I cannot count the number of times I have had probes in the innards of some machine, and turned my head to read the meter... and been unable to read it. Black digits on a green-black background. For me, a backlight is the greatest thing since sliced bread.Thanks again, all - Charlie

author: Fungus
author_rank: Super Contributor
timestamp: November 30, 2017, 01:39:29 pm
content: Quote from: CharlieWorton on November 30, 2017, 06:44:13 amIt's just 10 values on the display.nb. That value is for absolute accuracy, ie. against a fixed voltage standard.In theory you can measure very small changes in readings (deltas) with full precision.

author: CharlieWorton
author_rank: Regular Contributor
timestamp: December 01, 2017, 04:10:32 am
content: And, just to stir the pot...Here's a quite interesting link to a "supposed" UT61E on Aliexpress:https://www.aliexpress.com/item/UNI-T-UT61E-AC-DC-RMS-Digital-Auto-Rang-Multimeters-With-Capacitance-Frequnecy-Measurement-RS232-Computer/32823979602.htmlThe case says UT61E. It also says 22000 counts DMM. And the ad identifies it as a UT61E.But the published specs only claim 12,000 counts... and the display plainly has 4 digits, not 5.Caveat Emptor. One of the nice things about buying through Amazon is that they back the product 100%. And they also deliver in the existing millennium, which hasn't always been my experience out of China.

author: Paul Moir
author_rank: Frequent Contributor
timestamp: December 01, 2017, 08:18:47 am
content: At the rate Canada Post is forwarding stuff from China Post, you'd be lucky to get it next summer!There was an intriguing multimeter from Canadian Tire that went on sale for ~$30, but unfortunately it has since been replaced with one by some other manufacturer. Otherwise there wasn't much interesting available in Canada for a reasonable price. Find yourself a nice boring Fluke for the next one and appreciate both sides of the divide.

author: exe
author_rank: Unknown
timestamp: December 01, 2017, 08:40:32 am
content: Quote from: CharlieWorton on November 30, 2017, 06:44:13 amI have one. It does have 22k counts, but accuracy is quite bad. You may need to mod it (e.g., install a better reference, replace trimming pot, etc).I'm still happy with my device, for temperature measurements I use a dedicated ~$10 device. Although, I recently bought Keithley 2000 for more precise measurements (and to calibrate other DMMs).

author: Nusa
author_rank: Super Contributor
timestamp: December 01, 2017, 11:33:38 am
content: One persons "quite bad" is another persons "fantastic", and you can't tell the difference unless youquantifythe error and compare it to the written specifications for the device. Most of the time you've gotten what you've paid for, no matter how you feel about it.

author: exe
author_rank: Unknown
timestamp: December 01, 2017, 02:27:03 pm
content: Quote from: Nusa on December 01, 2017, 11:33:38 amMine is more than 10 counts off, making the last digit only suitable for relative measurements. I don't want to go into details, curious reader may find a lot of information about stability and calibration in the Internet, including youtube or this forum.Quote from: Nusa on December 01, 2017, 11:33:38 amThis is my judgement (of specification, if you wish). I don't really care if it's in spec or not, I'm mostly interested in performance of my own device, my experience and "how I feel about it" (no offense). Also specs cannot cover everything (like, long-term drift for cheap dmm, speed of continuity test, etc). So, I don't mind when people express their personal opinion.

author: CharlieWorton
author_rank: Regular Contributor
timestamp: December 02, 2017, 08:05:17 am
content: From reading and watching, my take on the Uni-T UT61E is:-solid, sturdy, feels great in the hand-terrible high voltage protection; meter will (usually) die or (rarely) blow up when subjected to high voltage. Not recommended for electricians, or anyone that may regularly work with high voltage. The board was designed for better high voltage protection and has holes for both MOVs and larger fuses, but they have not been installed. At least one person has upgraded his meter himself.. Some have suggested that the meter sold in the European Union has the upgraded parts.-22,000 count provides extra degree of resolution (not accuracy).-meter is usually within spec from factory, but can be tuned to higher accuracy.-meter has no backlight (abysmally stupid) but ingenious EEVBlog contributor has created a nice proximity switch based solution.https://www.eevblog.com/forum/testgear/uni-t-ut61e-backlight-mod-with-touch-sensor-(tutorial)/-meter will output data to an RS-232 port on your computer. Note: no one outside of China has an RS-232 port on their computer. I've purchased an RS-232 to USB adapter, and will report on how it works. RS-232 ports can also be purchased on a PCIe expansion card. (They come from China, where they're apparently quite popular.)-Software supplied with meter is quite limited; a better choice is UltraDMM from ultradmm.com, which can be downloaded and used without cost.====================== 30 ===============I've also purchased this "High Precision Voltage Reference Module" from AliExpress for about $5.00.https://www.aliexpress.com/item/AD584-High-Precision-Voltage-Reference-Module-4-Channel-2-5V-7-5V-5V-10V/32672069416.htmlIt's an AD584 based unit which provides very precise 2.5, 5.0, 7.5, and 10.0 volt outputs. I haven't been able to find official precision or accuracy statements, but it is apparently superior to a silver oxide battery (which, I'm told, has a very flat response curve). My past experience with AliExpress leads me to believe that I won't see it until March; but when it shows up I'll report on the results.>Charlie

author: Towger
author_rank: Super Contributor
timestamp: December 02, 2017, 09:44:17 am
content: Quote from: CharlieWorton on December 02, 2017, 08:05:17 amThe level of input protection fitted on the 61E depends on who/where you buy it from. The problem is there is no way of telling from the outside. eBay 'specials' will probably have none, but the same model from a major 1st world equipment supplier will probably have the better protection fitted.

author: Fungus
author_rank: Super Contributor
timestamp: December 02, 2017, 01:32:31 pm
content: Quote from: CharlieWorton on December 02, 2017, 08:05:17 amThe el-cheapo 61Es on eBay have a lot of missing safety components.You can get 61Es with all the components present, etc,. but they cost over $100.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 02, 2017, 03:15:34 pm
content: True. If you watch that video you linked for the first few minutes, you can see the GS marked 61E.I attempted to add a back light to mine as well. UNI-T had wrote me some time later about a meter they offer that has this sort of feature now.https://youtu.be/S36LfKmSjKw?list=PLZSS2ajxhiQDrk4o1Y45auwK7LomjnNBUThis meter also has a really poor burden voltage. I think it was one of the worst of all the meters I had looked at. I made an attempt to improve it as well.https://youtu.be/14eHpHQxm54?list=PLZSS2ajxhiQDrk4o1Y45auwK7LomjnNBUTo be clear, I would never suggest anyone waste their money or time to modify a handheld meter because of the risks involved. These are really just for the bit of entertainment and educational value they may provide. If you want a better meter, I suggest you buy one.

author: CustomEngineerer
author_rank: Frequent Contributor
timestamp: December 02, 2017, 03:56:42 pm
content: Quote from: CharlieWorton on December 02, 2017, 08:05:17 amThere are quite a few of those modules out there, some seem to be more accurate than others. Generally seems the ones that have handwritten values are more likely to be legit measurements, while (at least some) of the ones with printed values don't seem to really have much relation to the actual value, and some have the same exact printed values (probably indicating they weren't actually measured).https://www.eevblog.com/forum/metrology/are-cheap-ad584-units-worth-it/https://www.eevblog.com/forum/testgear/cheap-chinese-ad584-voltage-reference-legit-cal-data-let's-find-out!/

author: s8548a
author_rank: Regular Contributor
timestamp: December 02, 2017, 04:40:53 pm
content: Quote from: CharlieWorton on November 30, 2017, 06:44:13 amHi,Please check with "Nmori87", still a few u1252a units left it seems.https://www.eevblog.com/forum/testgear/bunch-of-keysight-u1252b-meters-around/550/https://www.ebay.com/itm/Agilent-U1252A-With-Carrying-Case/292327996622

author: David Hess
author_rank: Super Contributor
timestamp: December 02, 2017, 05:59:46 pm
content: The closest multimeter on my list is the Amprobe 38XR-A which is 10,000 counts and costs $150.The variable input resistance of the UT61E for DC measurements kills it for me; once should have been enough for me to learn that lesson but it took a couple tries and many wasted hours and a few wasted days. What kind of specification is "around 10M"?Of course the Amprobe 38XR-A specifications unambiguously say 10 megohms but I wonder if that is true. Anybody have one to test?It is common for the least significant digit of a handheld multimeter to be irrelevant because of limited accuracy. Good ones allow you to disable it for extra measurement speed and I only enable it when needed.

author: HKJ
author_rank: Super Contributor
timestamp: December 02, 2017, 06:58:00 pm
content: Quote from: David Hess on December 02, 2017, 05:59:46 pmA typical input circuit is 10Mohm and then different resistors is connected from that to ground. I.e. input impedance is 10-11Mohm depending on range.

author: exe
author_rank: Unknown
timestamp: December 02, 2017, 09:09:19 pm
content: Quote from: David Hess on December 02, 2017, 05:59:46 pmUhm, I thought most DMMs are like this... It's either "around 10M" or >1G... At least ut61e is not the one with this "problem". If input impedance really an issue then either measure it, or buy a high-impedance meter, imho.I just checked mine, it showed 10.1Mohm in V range, and 8.68Mohm in mV range. I checked AN8008, it showed 10.05MOhm in V range, and ~4.6MOhm in mv range. I don't know if impedance changes with the range, measurement voltage was 3.5V (by my Keithley 2000).

author: HKJ
author_rank: Super Contributor
timestamp: December 02, 2017, 09:17:49 pm
content: mV range is often high impedance.xV range is usual 11Mohm (10Mohm+1Mohm)xxV range is 10.1Mohm (10Mohm+100K),Using any voltage higher than 0.xV to measure the impedance of the mV range will trigger the overload protection and give a considerable lower value (The mV range may have a 1Mohm resistor and then the overload protection).In my reviews I am very careful to use a low voltage when checking impedance of the mV range. This spoils the precision due to noise, but I can see if it is 10Mohm or considerable higher.

author: exe
author_rank: Unknown
timestamp: December 03, 2017, 01:55:44 pm
content: Quote from: HKJ on December 02, 2017, 09:17:49 pmI'm pretty sure my measurements were affected by this, btw... I was too lazy to check this.

author: David Hess
author_rank: Super Contributor
timestamp: December 03, 2017, 07:39:14 pm
content: Having a variable input resistance is typical for cheap meters because it simplifies autoranging. This is not a problem for manual ranging meters and higher quality autoranging meters where the input resistance is constant. Some meters disconnect the input attenuator entirely on the lowest voltage ranges which has advantages and disadvantages. None of this has anything to do with input protection except insofar as the input resistance will change under overload conditions.But if the specifications say "around 10M", then I expect the typical single ended autoranging divider which will vary between about 11M and 10M. If the specifications unambiguously say "10M" like on the Amprobe 38XR-A, then anything else is a lie which is why I asked if anybody actually knows; I would be very interested in a new handheld meter which has a real 10M input.My good meters have an input resistance of 10M within 0.1% no matter what range is selected.If this seems like an overblown concern, then consider how much time can be wasted making precision measurements with an external divider when the meter's input resistance changes with range.

author: HKJ
author_rank: Super Contributor
timestamp: December 03, 2017, 07:55:13 pm
content: Quote from: David Hess on December 03, 2017, 07:39:14 pmCalling Fluke meters cheap is not entirely correct. I just checked Fluke 179 and 289 and they both goes between 10 and 11Mohm.

author: exe
author_rank: Unknown
timestamp: December 03, 2017, 08:55:10 pm
content: Quote from: David Hess on December 03, 2017, 07:39:14 pmJust use calibration on all ranges. Honestly, for me it's more "an implementation detail", rather than a serious consideration.PS if probe loading is a problem, I think using 1Gohm DMM is a better solution.

author: Lightages
author_rank: Unknown
timestamp: December 05, 2017, 05:00:07 am
content: Price. Quality. Features. You can't get all for the same price. You need to pick what is more important to you. You have a budget that does not meet hat is available. The UT61E is probably the closest but I cannot recommend it for many reasons. If you want to spend more then I recommend the BM257S but it is a whole bunch more. But..... nobody ever complained about buying quality.

author: Russ
author_rank: Regular Contributor
timestamp: December 05, 2017, 05:19:25 am
content: I am a newbee here. But I am really liking my Eevblog/Brymen 235 meter.Russ

author: HalFET
author_rank: Frequent Contributor
timestamp: December 05, 2017, 06:42:51 am
content: Even some of the high-end the 7.5 digit meters change input impedance slightly when they range switch, but it's relatively speaking a lot smaller. Also you need an electrometer to spot it

author: David Hess
author_rank: Super Contributor
timestamp: December 06, 2017, 11:45:25 pm
content: Quote from: HalFET on December 05, 2017, 06:42:51 amThis only happens if the high impedance input buffer has excessive leakage. The leakage current creates a variable error term which is dependent on the variable parallel output resistance of the divider. I suspect this is a major contributor to the "+ digits" parts of the error specifications on most multimeters.Charge injection can also contribute to measurement errors of input resistance which is why I keep a couple of old multimeters around which do not suffer from this.I am still looking for a modern handheld multimeter which has a constant 10 megohm input resistance. I have found several which say they do but I am dubious. Uni-Trend for instance does on the ones that I checked and I do not believe them at all. B&K says their manual ranging models are 10 megohms which I believe but they are all low end models. I guess I will have to ask Amprobe directly about their 37XR-A and 38XR-A. To give Fluke credit, at least they say "about 10M" instead of just "10M".

author: David Hess
author_rank: Super Contributor
timestamp: December 07, 2017, 01:40:31 pm
content: Quote from: blueskull on December 07, 2017, 02:30:49 amMy complaint is about the variation in resistance and obtuse specifications detailing it rather than the magnitude as long as it is high enough. It is absurd (except to the marketing department) to have high resolution meters with a variation in input resistance which causes additional errors greater than the basic accuracy or the 2nd to the least significant digit between ranges. Too many times now I have either spent hours tracking down a phantom circuit problem (1) or helping someone else do so when it was the multimeter lying.As far as Fluke, what am I to think about the Fluke 25, 27, 83, 85, 87, and 88? One Fluke reference (2) warns about the variable input resistance of these meters but the manuals unambiguously say 10 megohms "nominal" without indicating that the input resistance is between 10M and 11.1111M and likely only "nominally" 10 megohms on the most sensitive range. My multimeters which have an invariant input resistance of 10 megohms +/-0.1% are "nominally" 10 megohms. That is marketing at its finest desiring to eat its cake and have it to look at. What the user does not know will not hurt them, or at least will not hurt Fluke. At least some manufacturers indicate greater than 10 megohms or list exact values. (3)The difference between 10 and 11 megohms may not seem like much; after all, they are both high, right? But what source resistance would create as much error as the multimeter's basic accuracy or even worse, 10 counts or more with a change of 1 megohm between ranges? For 1% it is about 100 kilohms. For 10 counts on a Fluke 87, it is about 5 kilohms!So Fluke is cheap except of course in price. They are not offering anything that their cheap competitors are not offering except their name and often less.(1) It is usually a non-linearity problem which appears to be caused by excessive input bias current or poor common mode rejection.(2) The manual for the Fluke 80k-40 high voltage probe gives detailed instructions for compensating for an input resistance other than 10 megohms. So just plug-in the value for the range and get a correction factor. Hmm, so what value do I use for "10M nominal"? Is it the same "nominal" value for all Fluke meters?(3) The Fluke 179 specifications say "> 10M" for all volt ranges. The Fluke 289 specifications say "10 M" for all volt ranges but is that "nominally" meaning it could actually be 11.1111M or something else? I do not know what to believe.

author: Fungus
author_rank: Super Contributor
timestamp: December 07, 2017, 02:01:49 pm
content: Quote from: David Hess on December 07, 2017, 01:40:31 pmThe reading would be wrong anyway so what difference does it make?Moral: Don't measure a 100k impedance voltage source with a "10 Meg" multimeter, nominal or otherwise. Reading voltages on high impedance sources needs special care/attention/tools.

author: David Hess
author_rank: Super Contributor
timestamp: December 07, 2017, 02:06:58 pm
content: Quote from: Fungus on December 07, 2017, 02:01:49 pmThe problem is not the reading being wrong. The problem is the reading being inconsistent between ranges beyond the accuracy specifications.

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 07, 2017, 02:44:14 pm
content: Quote from: Lightages on December 05, 2017, 05:00:07 amExactly, you won't regret buying a good one. It doesn't have to be a silly top end meter, but a decent one like the BM257s will last you a long time. It has all the basic features you'd want and many more, is nicely built, has a bar graph and can even do datalogging if you someday wish to do so. More importantly, it's safe. You can be stupid and you will not hurt yourself, and likely not hurt the meter either. It'll only cost you your pride and a fuse.It's better to have a few good tools than many tools you can't depend on. A good one will serve you 5, 10 or 15 years from now.

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 07, 2017, 02:45:32 pm
content: Quote from: Paul Moir on November 30, 2017, 07:09:00 amI'd hate to lose the backlight on any of my meters. Unless you have a lot of light on the bench, it can be convenient to have a backlight. If you're measuring things around the house or in the field, having a backlight is an absolute necessity.

author: David Hess
author_rank: Super Contributor
timestamp: December 07, 2017, 03:16:47 pm
content: That brings up another point. Our discussion of obscure issues like variation in input resistance may be interesting but is largely irrelevant for most applications. So is the number of digits and counts and basic accuracy. Sacrificing these things for toughness, quality, required features, and ease of use is a better trade off for most users.As far as LCD backlights, I have never found myself in a position where one was required.

author: HKJ
author_rank: Super Contributor
timestamp: December 07, 2017, 03:52:29 pm
content: Quote from: David Hess on December 07, 2017, 03:16:47 pmOn my bench I have put up enough light that I do not need backlight, but I have sometimes been in location where backlight was nice.

author: Fungus
author_rank: Super Contributor
timestamp: December 07, 2017, 03:58:50 pm
content: Quote from: David Hess on December 07, 2017, 03:16:47 pmYep, 0.5% is plenty for just about everything. Anything beyond that is nice but won't have much impact in real circuits.It's already way beyond the tolerance of most components used outside the test gear world.PS: The Fluke 87 is really only a 6000 count meter at heart. The trick is to be 6000 counts +/- 1.

author: Mr. Scram
author_rank: Super Contributor
timestamp: December 07, 2017, 05:41:05 pm
content: Quote from: Fungus on December 07, 2017, 03:58:50 pmAnd to still be that or close to it after 15 years.

author: Fungus
author_rank: Super Contributor
timestamp: December 07, 2017, 06:11:34 pm
content: Quote from: Mr. Scram on December 07, 2017, 05:41:05 pmThat, too.eg. After Joe's latest tests the Fluke 17B+ started looking less overpriced than before. All the other meters were falling apart or grinding themselves to dust after a few thousand twists of the knob, even the fancy Agilents. The 17B+ was basically fine even after the full 50,000 twists.

author: Helix70
author_rank: Unknown
timestamp: December 08, 2017, 11:07:03 am
content: You would have to pry my Flukes from my cold dead hands.

author: Russ
author_rank: Regular Contributor
timestamp: December 08, 2017, 02:31:48 pm
content: I am a newbie to all this and currently enrolled in a Mechatronics program. Can I assume that it will be awhile before I outgrow my Eevblog/Brymen 235 DMM? How does it compare to Dave’s new 121GW model?ThanksRuss

author: Fungus
author_rank: Super Contributor
timestamp: December 08, 2017, 03:29:08 pm
content: Quote from: Russ on December 08, 2017, 02:31:48 pmYes.