Is there a Open/Standard RS232 Communication Protocol to Talk to Multimeter's - Page 1
Forum section: electronics / testgear

author: imk
author_rank: Regular Contributor
timestamp: March 30, 2018, 08:25:01 pm
content: Hello,Was wondering if there is a open/common/standard protocol for talking to multimeters and list of multimeter that adhere to it please?Many thanks imk

author: ebastler
author_rank: Super Contributor
timestamp: March 30, 2018, 08:30:54 pm
content: I don't think there is anything like a de-facto standard; every manufacturer or chip designer seems to have their own idea. But the SIGROK project has figured out most of them:https://sigrok.org/

author: dacman
author_rank: Frequent Contributor
timestamp: March 30, 2018, 09:04:17 pm
content: Closest language to a common standard would be SCPI. Lots of meters use it (HP/Agilent/Keysight 34401A, 34410A, 34411A, 34460A, 34461A, 34465A, 34470A, Fluke 8846A, 8845A, Keithley 2000/2001/2002/2010/2015, Tektronix DMM4040, DMM4050, old Datron meters with an "S" in the model number, etc.).

author: Cerebus
author_rank: Super Contributor
timestamp: March 30, 2018, 09:18:30 pm
content: Yeah, that's about it. You'll either find a manufacturer specificad-hocprotocol, or SCPI.SCPI is, what I'd call, loosely specified - some commands are common and are implemented the same way on almost everything (e.g. IDN), others can be almost as vendor specific as the ad-hoc protocols. If the function required is documented in theSCPI standardthen you're good, if however an instrument has some facility or function that isn't adequately supported by the standard you tend to get rather random vendor extensions to SCPI.The SCPI consortium seems to have died, their web page now leads to a domain parking site and the IVI have taken over distributing the existingSCPI standard.

author: imk
author_rank: Regular Contributor
timestamp: March 30, 2018, 09:26:18 pm
content: Mmmm many thanks all for the input guys.I guess a MM with good GUI + RS232 is going to be hard to find.I almost clicked BUY, on a Brymen BM257s but download there GUI and wow unbelievably BAD.So don't know which way to go now, any ideas please.imk

author: Nusa
author_rank: Super Contributor
timestamp: March 30, 2018, 10:08:16 pm
content: Your initial question implied you might be willing to write your own, given the protocol. Sometimes that's available directly, sometimes not. If sigrok has figured it out, you can always extract it from there.What are your requirements? Note that virtually all remote applications are less responsive than the meter itself, if that's an issue. They can't update data any faster than the multimeter sends it.("GUI is BAD" may be true, but it's subjective and doesn't tell us much, especially when we haven't seen it.)

author: mdijkens
author_rank: Regular Contributor
timestamp: March 30, 2018, 10:44:52 pm
content: I had a bit of the same experience. Most software was bad design, trying to cram all the bells and whistles in a terrible non-intuitive UI.I was mainly looking for precision monitoring/logging of long charge/discharge/power-consumption tests.Therefore the meter just had to be precise and running 10-20h and send the measurements nrear-realtime to my PCI didn't need to control the MM via the PC, just the loggingI ended up buying a good old Fluke 45 bench MM for $80 and wrote a simple to use windows-application that just does what it needs to doYou can see my results here

author: imk
author_rank: Regular Contributor
timestamp: March 30, 2018, 10:57:29 pm
content: Hello Nusa and many thanks for reply.GUI is bad, well i downloaded it and installed and well the windows are not re-sizable so it either almost full screen for the graph or icon, so bad for me.As for writing I am almost convinced that i'll have to as what i have seen just looking at Tenama 72-7760 it seems somewhat better than Brymen.Thanks for the advice re sample rate but i was aware that PC ware speed is always going to a function of the MM speed.Sigrok looks in right sort of direction but think has a away to go yet.But lot of it seems to based on screen scrapper technology, basically looks at the display segments and parses them into values.All of which is less than i was hoping for, as i had in mind some industry standard where the actual Measurement Values where sent out preceded by some token.e.g. V=0.0135 or R=270321 etc etc.The other issues i have just thought of in my search is the PC interface, as initially i was looking for USB.But now i realize that because of USB limited range USB,PC+MM is really only good for bench work and RS232 would be better as can drive much greater distances at low speeds.e.g MM in garden measuring solar panel output with PC in my office :-)I am still optimistic ii'l find a MM that fits my now uplifted to £200 budget :-)Again many thanks and have a good Easter imk

author: imk
author_rank: Regular Contributor
timestamp: March 30, 2018, 11:00:43 pm
content: mdijkensMany thanks for that i'll have a good look at it tomorrow as sleep time now in UK, have a good Easter imk

author: Cerebus
author_rank: Super Contributor
timestamp: March 30, 2018, 11:22:59 pm
content: Quote from: Nusa on March 30, 2018, 10:08:16 pmI think we all know what he means. We've all encountered the kind of software that exists so that someone can put on the data sheet that an instrument comes with some software, and when you get to see it in operation you realise that it was written by the sticky fingered 13 year-old nephew of somebody in the marketing department and documented by somebody on a work experience placement.

author: Nusa
author_rank: Super Contributor
timestamp: March 31, 2018, 12:23:41 am
content: If you're not in a great hurry, you might consider waiting for the EEVblog 121GW, which seems to be in your price range. It's got bluetooth communications, a documented protocol, and an open-source app to talk to the meter. Among other features. Only thing is the huge kickstarter orders come first. I suspect it's still a month or two away from actually being in stock in the store. Dave will presumably announce it when he knows for sure.https://www.eevblog.com/product/121gw/

author: abraxa
author_rank: Frequent Contributor
timestamp: March 31, 2018, 07:50:04 am
content: If you feel like it, you could always check outhttps://sigrok.org/wiki/Sigrok-meterand if it doesn't offer what you need, extend it. That way, you'd get the GUI you want with lots of compatible DMMs and everyone else would get a nice DMM GUI as well.

author: mtdoc
author_rank: Super Contributor
timestamp: March 31, 2018, 08:48:47 am
content: For a Linux or OSX solution, you should have a look atQtDMM. In addition to the listed DMMs it is not difficult to get it to work with others. For example I’ve had it working with the surprisingly accurate and well built, low cost Digital DT-4000ZC / TekPower TP-4000ZC via it’s RS232 interface on a Raspberry pi. This makes a nice low power/low cost logging setup.

author: imk
author_rank: Regular Contributor
timestamp: March 31, 2018, 09:22:57 am
content: Hello abraxaMany thanks for the link, but had already found it, had a good look and thought same as you, write my own GUI and contribute.But what puts me off is Python as i am C/C++ developer and don't fancy learning another language too old and too busy :-)Unless you have a C/C++ interface/api then i would be interested.Again thanks imk

author: abraxa
author_rank: Frequent Contributor
timestamp: March 31, 2018, 10:12:58 am
content: Since libsigrok is written in C, there are C and C++ APIs as well:C:https://sigrok.org/api/libsigrok/unstable/index.htmlC++:https://sigrok.org/api/libsigrok/unstable/bindings/cxx/index.htmlIf you have any questions, you're also welcome to join us on IRC.

author: imk
author_rank: Regular Contributor
timestamp: March 31, 2018, 12:05:28 pm
content: Quote from: abraxa on March 31, 2018, 10:12:58 amSo abraxa you have my interest :-) re c/c++ GUi.But before i begin I need a sigrok MM, do you have any recommendations please.The Brymen BM257s looks good but think the BM8xx are great but getting a bit big for my limited desk space.Since thinking about i have decided that it is RS232 is way to go for me, as neither USB or Bluetooth give me the potential range and not really interested in a phone interface.Plus there are lots of rs232 to bluetooth/USB dongles out there.imk

author: imk
author_rank: Regular Contributor
timestamp: April 03, 2018, 10:58:39 am
content: Quote from: Nusa on March 31, 2018, 12:23:41 amHello Nusa,Well after much deliberation I think the 121GW is for me. Looks like a great MM that will fit my limited desk space and budget.What put me off initially was my mind was stuck in wire/cable mode inasmuch as i needed to connect the logging device (MM) to my PC and do it over multi meters (top of garden) hence only practical solution was to use RS232. Then i discovered the UNI-T 71D which some love and some hate as a solution, as i can log to the MM then upload later to me PC, so all problems solved.So now my mind having gone full circle back to the 121GW as been best of both world, only issue is the wait to buy one in the UK :-(Plus the software is open source so i can write my logger/PC 121GW interface. MEGANusa many thanks for the heads Up :-)