Inexpensive Benchtop DMM - Page 1
Forum section: electronics / testgear

author: forrestc
author_rank: Unknown
timestamp: March 04, 2015, 09:43:09 pm
content: I currently have a rigol DM3058E on my bench, soon to be replaced with a HAMEG HMC8012, which are both good high-quality precision instruments. But, it seems that for most measurements I keep grabbing the handheld DMM which lives on my bench just because it starts faster, and usually I'm just verifying that a voltage is within a percentage point or two (do you really need to know what the voltage is of that 3.3V rail to 6 digits?).I'd really like to find a inexpensive (and cheap) bench DMM which behaves more like a handheld DMM for those 99% of measurements which don't need a full DMM. I currently have a Fluke 8050A that I've been trying to use, but the LCD on is hard to read in my lighting conditions for whatever reason - possibly the darker grey LCD background isn't being lit well from the overhead lights, but other than that, it's not bad.What I'm looking for is (aka requirements):1) Decent, easy to read LCD (backlit is a plus, but not needed if contrast is good).2) Instant-on startup.3) Not crap accuracy. (note that I didn't say good accuracy).4) at least 1000 counts (no I didn't miss a digit there - I want to read 12V to tenths, 3 and 5V to hundredths)5) AC Powered, Front power on/off switch.6) Cheap. $100US would be nice. $200 is more than I want to pay. Somewhere in the middle (or lower) is ok.7) Benchtop (of course).Plus points for things like compact size, etc. I really want something I can turn on, take a reading or two, and turn off, and not fight the DMM. The precision units take forever to start, and interface can be a bit of a pain. The 8050A would be fine except the display (as i mentioned). Others, well I'm looking for suggestions for.So far the closest one I've found is the tenma 72-1055 (http://www.mcmelectronics.com/product/TENMA-72-1055-/72-1055) but I'm not completely sold on the giant LCD.The mastec 8040 would be better, except I HATE rear power switches.And so on.Any ideas for something I should look at?Thanks.-forrest

author: Wytnucls
author_rank: Super Contributor
timestamp: March 04, 2015, 10:25:53 pm
content: I don't get it. The Rigol DM3058E takes a whole 6 seconds to boot up. By the time you have located and grabbed your probes, it is ready for measurement.If you really need instant power on, get a decent portable DMM instead of a crappy benchtop instrument.

author: rdl
author_rank: Super Contributor
timestamp: March 04, 2015, 10:36:48 pm
content: I have one of these, except I got mine from Electronix Express and it's branded RSR:www.ebay.com/itm/Mastech-M9803R-Bench-type-Top-LCD-Digital-Multimeter-LCD-Display-Data-Hold-/111379455301I bought it about 10 years ago. It works fine, starts almost instantly, display is large and easy to read, and has a backlight if you want. Runs off two types of battery power or plug it in the wall (standard IEC type detachable cord).It matches the readings of my Fluke 87-III almost every time I've compared them. I've never opened it up, so I have no idea how well it's made or how safe it is. When that's a concern, I use the Fluke.

author: edavid
author_rank: Super Contributor
timestamp: March 04, 2015, 10:50:43 pm
content: If you like the Fluke 8050A, check out the Fluke 8600A... similar except it has a bright LED display (no TRMS though). Should be under $20, so you can buy 2 or more of them.You could also look for a Fluke 8840A, which is a very nice meter, but many of the ones you find now have a tired VFD.Hmm, you could also replace the 8050A displaywith LEDsora backlit color LCD.

author: forrestc
author_rank: Unknown
timestamp: March 04, 2015, 11:42:44 pm
content: Quote from: Wytnucls on March 04, 2015, 10:25:53 pmCrap. I wonder what is up with mine then. It's well over 30 seconds, and doesn't seem all that consistent. I haven't really been happy with this unit since I got it due to some general weirdness (which is oddly unlike the other rigol gear I have) - now I'm wondering if the behaviour is somehow related to this particular unit.Under 10 seconds is acceptable. 30-60 is not.I'm going to do some poking around and see if there's a firmware update or factory reset or something similar in case it's a software issue.-forrest

author: nctnico
author_rank: Super Contributor
timestamp: March 04, 2015, 11:47:28 pm
content: Get a VC8145! It matches your description perfectly. I got one and I'm so happy with it I bought another one (so now I have two).www.ebay.com/itm/Digital-Multimeter-VICHY-VC8145-4-7-8-Bench-Top-Meter-PC-DMM-80000-Digit-D0123-/130897503021BTW I would go for at least 10000 counts (4.5 digit). In the 20A range you can still see mA.

author: rdl
author_rank: Super Contributor
timestamp: March 04, 2015, 11:49:47 pm
content: BTW, if the Mastech 8040 is like the M9803R, it can be turned on and off by the front rotary knob, just leave the rear switch in the on position. It does still draw about 0.8 watt when the front knob is "off" and the rear switch is "on".

author: codeboy2k
author_rank: Super Contributor
timestamp: March 04, 2015, 11:49:52 pm
content: I have two Keithley 197A benchtop DMM's that are my goto DMM's on the bench...I agree with you, you don't need to know the 3.3 V rail is 3.304 or 3.314 ... for example. Startup is instantaneous, just a power switch and it's up in less than 1 second. Of course if you want more accuracy it needs to warm up, but it's ready in less than 1 second.These are 5.5 digits and you can get them on eBay for less than $100. For one of my units, the seller was asking $75 USD, so I bought it. For the other, the seller was asking $350, I offered him $75, he acceptedOften times these have dim back lights, but that can be replaced easily (even color changed to something else) with a $7.00 replacement EL panel from eBay.One of mine had a very dim EL panel and I replaced it. The other was ok.

author: nctnico
author_rank: Super Contributor
timestamp: March 04, 2015, 11:58:25 pm
content: Beware the old bench DMMs with LCD often are difficult to read and in general don't have features like dual display (AC+DC for example or AC+frequency), backlight, continuity beeper, temperature measurement, etc.

author: codeboy2k
author_rank: Super Contributor
timestamp: March 05, 2015, 12:25:46 am
content: Quote from: nctnico on March 04, 2015, 11:58:25 pmyes, actually I just took a look at that eBay listing you linked to, it's rather well priced, at $152 + 9.99 shipping... the Keithleys I bought were $75 + between $35 to $40 shipping, so that's $115 max right there. At $50 more, you can get the VICHY VC8145. You lose a digit, but you get all the features you mentioned, a great big dual display + bright backlighting.I think that eBay listing is quite a bargain.

author: forrestc
author_rank: Unknown
timestamp: March 05, 2015, 12:33:41 am
content: Quote from: forrestc on March 04, 2015, 11:42:44 pmUpdate - did a factory reset and now it starts in about 6 seconds and behaves better. I still don't trust it (yet), but at least it seems like a property behaving instrument.

author: EEVblog
author_rank: Unknown
timestamp: March 05, 2015, 01:20:55 am
content: An old school Fluke 37?

author: edavid
author_rank: Super Contributor
timestamp: March 05, 2015, 01:33:13 am
content: Quote from: EEVblog on March 05, 2015, 01:20:55 amIt's not even as good as his 8050A... only 3.5 digits, and the LCD is no better.

author: forrestc
author_rank: Unknown
timestamp: March 05, 2015, 02:23:35 am
content: Quote from: edavid on March 05, 2015, 01:33:13 amI'm really kinda intrigued with replacing the LCD on the 8050A with 7 seg LED displays as linked to by one of the previous posters. The GLCD replacments are a bit outside what I want to do, but a few hours hacking in 5 digits of LED's is an intriguing idea. I like the 8050A, just don't like the display.On the other hand, now the DM3058E is actually booting in a handful of seconds and seems far more stable, I'll probably see how it behaves at least for the near term. (it's amazing how asking one question often solves another problem you didn't know you had)... Still going to get that Hameg though..The other use I have for these is that I fairly often need 2-3 DMM's at once. The Hameg HMC8012 solves some of this (especially if part of it is DC+AC Ripple, or current+amps, or voltage+frequency, etc.), so does the DM3058E. If I modify the 8050A, I might be fine with what I have.That said, I seem to collect DMM's for some reason - and this thread is pointing me toward some great older DMM's I didn't even know existed.

author: Wytnucls
author_rank: Super Contributor
timestamp: March 05, 2015, 02:37:45 am
content: The DM3058E can do voltage and current at the same time, saving you one meter.

author: EEVblog
author_rank: Unknown
timestamp: March 05, 2015, 02:50:57 am
content: Quote from: edavid on March 05, 2015, 01:33:13 amHe said he only needed 1000 counts.I don't know about the LCD comparison, but 37 I used to have had excellent contrast IIRC.

author: jwm_
author_rank: Frequent Contributor
timestamp: March 05, 2015, 02:59:19 am
content: I think you may get more bang for your buck with a used keithley than a used fluke. Both will be fine meters, but I think the fluke name commands more of a premium on ebay than keithley for similarly speced meters.Oh, and for readability. find a model with a VFD display. Better than any LCD/LED when it comes to readability under different conditions.EDIT: after a quick perusal, I am not sure there is a VFD one in your price range. I'd love to be proven wrong though.

author: retiredcaps
author_rank: Super Contributor
timestamp: March 05, 2015, 03:06:47 am
content: Quote from: forrestc on March 05, 2015, 02:23:35 amAnother one.http://mrmodemhead.com/blog/gallery/fluke-8050a-led-conversion/

author: codeboy2k
author_rank: Super Contributor
timestamp: March 05, 2015, 06:10:28 am
content: Quote from: 3roomlab on March 05, 2015, 05:09:06 amYeah, the broken ones can go for $25-$50.. be careful with shipping, one guy was listing a WORKING one at $25 for about $200 shipping from the USA. I'm in Canada and I know that these things can ship for about $35, so if the seller charges $35 to $50 shipping it's reasonable.

author: nctnico
author_rank: Super Contributor
timestamp: March 05, 2015, 12:54:20 pm
content: If you want to go cheap: Many years ago I bought an HP3466A 4.5digit bench DMM for $40. It is older but is has a LED display which is much easier to read.

author: codeboy2k
author_rank: Super Contributor
timestamp: March 05, 2015, 03:17:26 pm
content: I might add one of those. I was at one time considering doing a LED conversion on one of my Keithleys ... I might still do that one day.

author: codeboy2k
author_rank: Super Contributor
timestamp: March 06, 2015, 03:42:30 am
content: Quote from: 3roomlab on March 05, 2015, 07:18:19 pmThe 197a for $29.90 , if it has a good shipping price, that's a good deal. Like I said, some guys price it really low but have shipping prices over $200 or more.The Mooshimeter only claims 0.5% accuracy. The TL431 in sot-23 is 0.5% initial accuracy, and cheap at $0.10 @qty 1000. If they later do a factory trim or a closed-case calibration procedure they can improve it. It's 20ppm, so that's 0.002% TC, it's actually a pretty decent reference, so maligned in the pressOne day they can offer a closed-cased calibration and could reach 0.05% if all the parts in the signal chain were ready to support that accuracy.