Benchtop DMM advise needed [1 uA to 10 A, 2W/4W, U/I dual display, LabView] - Page 1
Forum section: electronics / testgear

author: Professzore
author_rank: Contributor
timestamp: July 22, 2018, 11:31:44 am
content: Hi All,I've spent some time here reading the forum about different bench DMMs. I found out that a good old may be a better choice than a brand new. It's clear. On the other hand, I have some requirements on my list, and some limitations on international orders, so either up-to-date technology (past 2010) and direct availability (no ebay/aliexpress) are key points.First of all, what I need:5 1/2 digits,50 000+ counts (100k counts are even better),Current: 1 uA significant precision on DCI, measuring capability up to 10 A DC,no special need for Voltage (mostly DC up to 24 V),True RMS (AC, AC+DC),2W/4Wmeasuring capability on resistance,capacitance,dual display(U/I measurement at the same timeor U/Freq readings),selectable iteration times (sample averaging),manual/auto range,max/min holdordirect stats to max/min/avg/dev,10 measurements/second logging feature via USB and/or serial(LabView, Matlab or Excel, preferably U, I, and if it accepts any thermocouple, themperature),2-5 measurements/second internal logging/history may be a nice feature, not a must,REL (better if manual setting is also available),GPIB with pass/fail, rise/fall configurable output and trigger input may be a nice feature,€500 / $600 budget(brand new) without special test leads, (and a maximum +100 if all requirements are met with some extra feature),available within the EU.I've made a huge research. Most quality manufacturers (Fluke, Agilent/Keysight, Keihtley) are out of scope due to price and/or the lack of some features (logging). And it is still possible that I've missed something.GW Instek GDM-8351seems fine, except the limitation on current measurement (200 mA lowest range may barely enough for 1 uA significant precision). Loved the external digital I/Os.http://www.gwinstek.com/en-global/products/Digital_Meters/Benchtop_Digital_Multimeters/GDM-8351It is not on the list anymore because the lack of precision.Rigol DM3058Eis also seems good, except the lack of GPIB (external trigger input and pass/fail output)https://rigol.eu/products/digital-multimeters/dm3000/Any suggestion, advice or hint are warmly welcome!Background: embedded hardware development, sometimes for ultra-low power applications.Thanks for your suggestions.Yours Sincerely,Tamás

author: rsjsouza
author_rank: Super Contributor
timestamp: July 22, 2018, 01:47:08 pm
content: Perhaps the Siglen SDM3055 could be an option for your current range? It says the current range goes.from 200uA to 10A and is dual display.http://www.siglent.com/ENs/multimeter/SDM3055

author: nanofrog
author_rank: Super Contributor
timestamp: July 22, 2018, 04:03:14 pm
content: The GDM-8351's lowest range is10mADC (not 200mA), and the resolution is 100nA per the specs on their website. So it should do you quite nicely.FWIW, I've it's older brother (GDM-8251A). Checked eBay, and there's a couple of sellers that will ship to Hungary for around half your budget (not sure about customs fees though). They have selectable input voltage PSU's, so you'd only need the correct IEC cord to get it running (ports = RS232 & USB).Hope this helps.

author: Professzore
author_rank: Contributor
timestamp: July 22, 2018, 04:08:01 pm
content: Hi,Quote from: rsjsouza on July 22, 2018, 01:47:08 pmAmong many other low-budget models, Siglent was on my preliminary list. Later I deleted, due to some reasons (for example, it's a Keysight/Agilent copy with some design problems). I've also deleted RS Pro (re-brandes Siglent), AxioMet, UNI-T.I have some Rigols now (oscilloscope and PSU), and meanwhile they are not free of problems, I can deal with them.Thanks for the reply.Tamás

author: thals
author_rank: Contributor
timestamp: July 22, 2018, 04:19:17 pm
content: Do you need 1uA DC resolution or accuracy? If resolution is sufficient, the AIM-TTI 1908P might also fit the bill:https://www.aimtti.com/product-category/multimeters/aim-1908Otherwise the GDM-8351 with 0.05%+15d on the 10mA range is also not sufficient.

author: Professzore
author_rank: Contributor
timestamp: July 22, 2018, 04:26:13 pm
content: Hi,Quote from: nanofrog on July 22, 2018, 04:03:14 pmThat's the point. I do not know how could I make this mess... Thanks for the memo! :-) Really useful.By the way. With a short calculation: anything over 50 USD (including postage) should be handled by local authorities. Customs +14 percent, VAT +27 percent. And there are some fixed costs for the service. So, it may be +50%. Furthermore, if I may be open minded for an overseas order, I may go for a Fluke / Keysight / Kithley.Tamás

author: Professzore
author_rank: Contributor
timestamp: July 22, 2018, 04:51:48 pm
content: Hi,Thanks for the reply.Quote from: thals on July 22, 2018, 04:19:17 pmAccuracy. (At least) one decimal over the least significant digit.Quote from: thals on July 22, 2018, 04:19:17 pmNow I can't reach it (unknown reason), but will make some research later on.Quote from: thals on July 22, 2018, 04:19:17 pmIt is barely possible to go down to the desired (almost) 500 nA range. Most of the measurements I made and found useful was around 10-100 uA. Based on the specs, +0.05% is negligible, 15 counts is +/- 2 on the 1 uA measurement. If everything else is fine, I can accept it.Anyway, your answer also helped me to get closer to the right decision.Tamás

author: tautech
author_rank: Super Contributor
timestamp: July 23, 2018, 09:22:45 pm
content: Quote from: Professzore on July 22, 2018, 04:08:01 pmYes IF you haven't kept up to date with the many improvements since most reviews were done on them.They're a much better product now.

author: Professzore
author_rank: Contributor
timestamp: July 26, 2018, 05:59:03 am
content: Hi,Quote from: tautech on July 23, 2018, 09:22:45 pmThanks for your reply.You are right. I've seen a lot of improvements in the last 10 years, both on ideas and on build quality. On the other hand, let me explain one of the software/fw problems on my Rigol DP832. Voltage limit works only on active output. You can set any voltage, even over the limit, then turn the output on, and it will shut down only after a +5-30% overshoot. I bet, it may be way better to write a code which doesn't let the output turn on if the set voltage is higher than the voltage limit. Or even do not let you set any voltage over the limit. I can deal with, I can live with it. I do not want to meet similar stupidity on a bench multimeter.From another point of view. There is no any official way to get maintenance/service/calibration to a Rigol in Hungary. There are a couple of resellers, most are working from the German centre, so each unit must be sent back to Germany for inspection, repair and for calibration too.Anyway. If you have any hint or advice (make/model), I will really appreciate your help and put the suggested unit back to my list for deeper analysis.Yours sincerely,Tamás

author: tautech
author_rank: Super Contributor
timestamp: July 26, 2018, 09:19:26 am
content: Quote from: Professzore on July 26, 2018, 05:59:03 amSDM3055.It meets your spec.https://www.siglenteu.com/digital-multimeters/sdm3055-5-%C2%BD-digits-dual-display-digital-multimeters/On the webpage you can download the datasheet and the service manual to check both spec and calibration requirements.Your calibration house can obtain the EasyTest software and the Cal equipment used at the factory is listed on the Cal sheet that you get at purchase.Right now I'm sold out of 3055 so I can't say for sure what that equipment is used, however as some guide the SDM3065X uses a Fluke 5522A Multi product calibrator.Who are the calibration providers in Hungary ?Maybe if you contact Siglent in Hamburg they can tell you some they are already using.

author: Professzore
author_rank: Contributor
timestamp: July 26, 2018, 07:40:18 pm
content: Hi,Quote from: tautech on July 26, 2018, 09:19:26 amAbsolutely enough.At 200 uA range accuracy is 0.055 + 0.005 (% of measurement + % of range). At 200.000 display precision and 1 uA measurement, it means +/- 0.010(55)overall precision, which is one whole digit better than the requested 1 uA significant precision.I'll make some deeper research on PC-log/-trend side early next week.Quote from: tautech on July 26, 2018, 09:19:26 amThere are a lot of providers with different equipment and different services. Most of my devices are way within the 2-year period and haven't yet made a whole market research for the possibilities (I have only Rigol, but switched one supplier to another recently, and the new one have some in-house calibration offer -- but I do not know anything about it yet). So, there is a wide range of possibilities. The big question is availability and price. My above mentions about Rigol is about the old supplier so it may be better with the new one.I am very thankful for your answer and your suggestion too.This is still a learning curve for me. If you may have some time, I may be very pleased, if you could write a few lines about my current idea. So,what ifI...expandthe DCI limitdown to the nA range with 10 nA significant precision,expand to 6 1/2 digits,doubles the budgetup to the€900–1000 range,simply forget the “dual measurement of U and I” idea for practical reasons,and say/guess that aKithley DMM6500may be a good/best choice?https://www.tek.com/tektronix-and-keithley-digital-multimeter/dmm6500The only relevant limitation is capacitance measurement (too small range), but extra features like capturing live signals with 1 MS/s may be extremely useful for my main development goals (ultra low-power IoT). This is what I was going to make on the PC-side. And, finally, as far as I know, Siglent and Tektronics/Kithley are in two different leagues.Thanks in advance.Tamás

author: tautech
author_rank: Super Contributor
timestamp: July 26, 2018, 08:14:27 pm
content: Quote from: Professzore on July 26, 2018, 07:40:18 pmWell yes of course 6.5 digits will give greater precision and SDM3065X is only a little past your original budget @ 689 Euro. Also the 16ch scanner card model now fits you enlarged budget.All the SDM's can do dual measurements. Their measurement combinations are listed in the manuals.IIRC when Defpom did a review with mine (he ended up buying it off me later) he used Temp measurement mode to get readings into pA ranges. I might have that wrong but watch the video and you will see. It was video #223.https://www.youtube.com/user/TheDefpom/videos

author: nctnico
author_rank: Super Contributor
timestamp: July 26, 2018, 08:31:15 pm
content: Quote from: Professzore on July 26, 2018, 07:40:18 pmIn this price range I'd also look at the Keysight 34461A.

author: Brad O
author_rank: Regular Contributor
timestamp: July 31, 2018, 03:59:36 pm
content: I may be a little biased towards the DMM6500... but since you mentioned you will be using the DMM for low-power IoT, I wanted to show you our application note for just this (in case you haven't seen it yet):https://www.tek.com/document/application-note/data-logging-power-profiles-wireless-iot-and-other-low-power-devicesPage 6 starts talking about streaming data to a PC. The DMM6500 also offers a dual measurement view, even though you removed that requirement from your updated specs.For measuring capacitances larger than 100uF, you could use the diode test function to source a current and measure the voltage, you could then do your own dV/dt math to get the capacitance (or write a script to do all that for you). That method would not be spec'd, but it would get you close to the correct value. This should be possible with other DMMs, but I know you can do it with the DMM6500.

author: Professzore
author_rank: Contributor
timestamp: July 31, 2018, 07:44:20 pm
content: Quote from: Brad O on July 31, 2018, 03:59:36 pmI simply cannot make any guess why?!By the way. Now I am reading the 107-page user manual. I'll be back for all other papers within a few days.It is a hard decision because my budget is rather limited and I do not have any direct contact with Keithley distributor in Hungary (only online resellers like Farnell for example). By date, it is the best match for my measurement needs (as precisely as I was planning to make an own touch-screen for a lower-end DMM for easier data-logging).I may be very pleased to have any chance for a short testing...Thanks for your support.Tamás

author: Professzore
author_rank: Contributor
timestamp: August 02, 2018, 07:01:43 am
content: Hi,Now I have borrowed this (see below).After a few minutes of pure joy investigating all the possibilities, I'm more than just satisfied.On the opposite side, I have to work hard to find any working solution to high-speed (10 Sa/s) uA resolution logging on my desktop PC. By the way, I love 6 1/2, as well as Keithley too.

author: Professzore
author_rank: Contributor
timestamp: September 14, 2018, 03:43:19 pm
content: Hi All,First, I want to say a hugethank youfor all who read and also who wrote an answer to my question.After many nights spent to clearly figuring out my requirements, my final decision became Keithley DMM6500 from Tek. It isway overmy original budget, but I hope that the extra money will bring me extra benefits, and my soon-to-come IoT and low-power developments will be done faster and more efficiently.Yours sincerely,Tamás