121GW IS VERY SLUGGISH - Page 1
Forum section: electronics / testgear

author: daveyk
author_rank: Frequent Contributor
timestamp: July 11, 2019, 04:30:05 pm
content: I had to buy one from Dave base on its specifications and his demonstrations of it.I find it a little tricky to use, but once past some quarks, I find its resistance very sluggish to the point you can not use the meter to trouble-shoot. For instance:I put my 121GW across a 1K resistor in-circuit. 1st it reads 16.6MOhms and then about 2.5 seconds later the reading changes to .9977K.That first resistance reading varies ever time. Sometimes it reads 16MOhm, then 1.5 seconds late 33K, and then another 1 to 1.5 seconds later, the actual resistance.Is this normal behavor? I am use to DVMS responding fairly quickly. If I use my bench DVM, ot other portable DVM, they get .99K reading bang instantly.If I put the two leads together, it's a good three seconds before I get a reading a few milliohms. This is anoying as heck.I found this meter is bang on, and quick, with my calibrated voltage standards and frequency standards (at least the ones below 1MHz). I do find it a little irritating that to read DC, I have to put the switch to "V" and then press the mode button twice, but I can learn to live with that.Anywho, is there a FIX for the very sluggish ohms readings?

author: e0ne199
author_rank: Regular Contributor
timestamp: July 11, 2019, 04:38:08 pm
content: NOTE: This message has been deleted by the forum moderator Simon for being against the forum rules and/or at the discretion of the moderator as being in the best interests of the forum community and the nature of the thread.If you believe this to be in error, please contact the moderator involved.An optional additional explanation is:

author: rsjsouza
author_rank: Super Contributor
timestamp: July 11, 2019, 04:45:36 pm
content: The 121GW started with a slow auto range, but I suspect several issues were fixed since then. I would look at the three sticky threads at the Test Gear forum room:https://www.eevblog.com/forum/testgear/That said, measuring things in-circuit is not a good way to check a meter's capabilities - too many things can go wrong and influence your ability to properly evaluate the meter.

author: gnif
author_rank: Unknown
timestamp: July 11, 2019, 04:47:12 pm
content: @e0ne199, useless comments like that to questions are not acceptable,@daveykis looking for a fix/solution for the 121GW, replacing it is not a fix.@daveykthis is a known issue with the 121GW and has been reported here numerous times, a firmware update may fix it, I believe there is even a hacked/modified firmware that improves the auto ranging feature that Dave himself tested on his alt YT channel. Someone else here might be able to comment further on this.

author: daveyk
author_rank: Frequent Contributor
timestamp: July 11, 2019, 04:57:33 pm
content: "this is a known issue with the 121GW and has been reported here numerous times"Thank you gnif. I did use the search function but nothing came up and I am working today and do not have time to search through 1000's of message manually.Okay, I hit the range button several times until a "K" comes up in the right side of the display and then it seems to read the resistance very quickly."measuring things in-circuit is not a good way"In this case it is necassary. I am trying to track down a noise problem on a UT instrument PCB. I see the 00-LEMO connectors have been changed before by someone. The issue is probably a tiny trace torn. Each connector has a 1K resistor in parallel with it. I have seen were the grounds have come disconnected between the resistors and the connectors or even between the connectors. So I was going to do a quick check of center pin of the 00-LEMO to several different ground locations and make sure 1K (or slightly less was read). I am just looking for crude readings, but higher than beep beep continuity mode. In autorange mode, I thought "Ah hah! The freaking ground is bad!" then 3 seconds later it wasn't bad. That got me in to putting the lead together and seeing it take 3 seconds to read ~0 ohms.Again thank you. I was disheartened by the first smart ass comment and just about said "screw-it" and grab the old fluke or the free Harbor Frieght meter - lol.Dave

author: rsjsouza
author_rank: Super Contributor
timestamp: July 11, 2019, 06:11:17 pm
content: Quote from: daveyk on July 11, 2019, 04:57:33 pmI now understand the boundary conditions, but you quoted an incomplete version of my sentence which hints that I discount any in-circuit measurements. I've seen too many users with poor measuring techniques blaming the equipment for its perceived faults.

author: DaJMasta
author_rank: Super Contributor
timestamp: July 11, 2019, 06:28:59 pm
content: Have you tried the most recent firmware? A month ago or so there was a new firmware released that did improve autoranging speed, and while it may not be quite the performance you're looking for, it could be an improvement.I'd be curious if the firmware could be modified to extend the continuity mode to a higher range, like 1k ohm or so, making it usable for smaller resistor values and things. I've thought for a bit now that an adjustable threshold for the continuity tester could be a really useful feautre - like turning it down to 40 ohms or so to avoid continuity readings over termination resistors or turning it up for applications like this, but I don't know if the ranging settings used for continuity mode would support that.

author: BU508A
author_rank: Super Contributor
timestamp: July 11, 2019, 06:59:59 pm
content: Quote from: daveyk on July 11, 2019, 04:57:33 pmGranted, the search function of the forum is not the best in the world but maybe this little trick will help next time:go to google --> enter in the search field <search pattern> site:www.eevblog.com/forum/This could improve your search results (search pattern without the <> of course)HTHMounty

author: daveyk
author_rank: Frequent Contributor
timestamp: July 11, 2019, 07:02:22 pm
content: "Have you tried the most recent firmware? A month ago or so there was a new firmware released that did improve autoranging speed, and while it may not be quite the performance you're looking for, it could be an improvement."I see Dave has version 2.0 on the EEVBlog web site (yet meter that just arrived is two versions behind); but that's okay; cool.Is there any limits on the uSD cards? I am order two 64gb with SD adaptors from Amazon; I'll have the Saturday. I could run to walmart 5 minutes from here, but I don't feel like it - lol. I almost ordered a 256GB uSD card, but then thought some devices might have problems reading one that big. I don't know if the meter would or not. I hope it's okay with 64gB (Heck I still use Windows XP on test computers and the Thumb Drives that Walmart sells won't work under XP. I am also worried about Window 7 that my work lives on).Thanks again and take care.

author: windsmurf
author_rank: Frequent Contributor
timestamp: July 11, 2019, 07:13:50 pm
content: Is the source code for the firmware available? It would be really nice if we could modify the firmware to customize the meter functions to suit our exact needs.

author: bicycleguy
author_rank: Frequent Contributor
timestamp: July 11, 2019, 07:45:20 pm
content: I believe the meter comes with a 8 gig micro SD card. Try the log function. If it works, its already installed. Also it may not be obvious to you yet, (it is to me), but read the manual. This meter is a little more complicated ( feature loaded ) than a typical meter.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 11, 2019, 09:31:56 pm
content: Why dont you post in the 121 gw threads instead ??

author: daveyk
author_rank: Frequent Contributor
timestamp: July 11, 2019, 09:42:58 pm
content: "I believe the meter comes with a 8 gig micro SD card."You know what, I think I do remember seeing the uSD card; I forgot about that - oops. I don't have a uSD to SD adapter to hook uSD to computer to put FW on it, or if I did (probably did); I have no idea where it would be at. I'll give one of the 64gb uSD to my kid for his droid Phone. Now an adaptor, I may have been able to go to Wallyworld for, but now I will wait until Saturday."Also it may not be obvious to you yet, (it is to me), but read the manual. This meter is a little more complicated ( feature loaded ) than a typical meter."heh heh heh, I did download it, and need to print it out [ What read it??!! ]. I am anxious to update the firmware in it. Even with it's quarks, I can work around them. I wish the "V" function defaulted to DC rather than AC (Wait!! It remebers the mode I had it in when last turned off! Wow!, NEVER MIND - LOL). This meter does have great resolution (4.5 digits), and it's bang on my Model 249 Scope Calibrator's reference voltage output and Frequency Outputs, agreeing 100% with my HP34401, which was just calibrated (with adjustments!!) and certified by Spectrum Technologies a few month back. I hadn't planned on keeping this as a calibrated asset, but once I update it and learn it better, I will probably drop it off for an ISO17025 certification (that costs as much as the meter did).Thanks again for your assistance.Dave

author: daveyk
author_rank: Frequent Contributor
timestamp: July 11, 2019, 09:46:37 pm
content: "Why dont you post in the 121 gw threads instead ??"At the time, I could not find an answer to my query in those threads, using a forum search function. Plus there was a whole s-ton of message to page and page through to look for an answer to this 3 second suggish resistance readings.I know now to manual range for what I need and it is fast. I will try new Firmware on Saturday (hopefully).If someone want to delete this topic, I created, or blend it in somehow to the other topics, please do. There were many who helped me in here; thank you all.Dave

author: e0ne199
author_rank: Regular Contributor
timestamp: July 12, 2019, 01:24:55 am
content: Quote from: gnif on July 11, 2019, 04:47:12 pmi am sorry i thought firmware v 2.0 was still slow for him so i gave that recommendation, and i don't think my answer is useless because there are 3 sticky threads about 121GW and i thought he had read them and still made a new thread to complain about the sluggishness of 121GW..

author: gnif
author_rank: Unknown
timestamp: July 12, 2019, 04:35:23 am
content: @e0ne199 You might think that replacing the meter is a "fix", but I guarantee you that most of the community here would disagree and some including myself find such comments lazy and offensive.

author: daveyk
author_rank: Frequent Contributor
timestamp: July 12, 2019, 01:28:51 pm
content: "Have you tried the most recent firmware? "Hello again DajMasta. I did mange to upgrade the firmware to 2.0.Yes, it is still not a speed demon in autorange resistance, BUT what this firmware did which it a total fix in my mind was to blank out the one or two incorrect readings until it settles on the correct one. I can handle a 1.5 second delay as long as nothing is displayed until then (I confuse and make incorrect assumptions easily based on false readings - you want concentrate on the circuit you are repairing and not to have to concentrate on the tool you are using). Perfect fix! Thank you kindly for your (along with others) suggestion . I'm not use to having to do that to a DVM, but this meter is bleeding edge and is really chalked full of features other handheld DVMS are missing.Again, I appologize for starting my own thread, but you guys are the greatest and are an uncalculable valuable resource!Dave

author: daveyk
author_rank: Frequent Contributor
timestamp: July 12, 2019, 01:40:28 pm
content: "i am sorry i thought firmware v 2.0 was still slow for him so i gave that recommendation, and i don't think my answer is useless because there are 3 sticky threads about 121GW and i thought he had read them and still made a new thread to complain about the sluggishness of 121GW.."eOne199, appolog accepted. I was basically stressed out and pulling my hair out (both with this meter and an instrument that I was working on), and I did find that responce from you a smart arse comment, which did not help, and quite frankly upset me (yaa I know toughen up a grow a pair - lol). I was just not in the right place mentally yesterday.I basically just unbox this brand new meter and it had thrown me for a loop display one or two incorrect resistance readings before finally displaying the correct reading 3 second after probing the resistor. #1: I didn't even consider firmware as it is brand new. #2: I was worried that is was defective (that happens). #3: I did search and could not find any messages with "sluggish" in them. #4: there is a s-ton of messages to read through and I am not a fast reader. I would love to read all of the message and may start that when traveling later today.These guys on this forum are great. Even though, technically, I guess I should not have started a new topic thread, they were great and came to my rescue. My problem was confirmed to be software and not a hardware issue with a new meter. Even a suggestion to put in manual range was excellent. It is up an running fairly good now and I am happy with it.Take care,Dave

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: July 12, 2019, 03:26:08 pm
content: It sounds like the inventory might have old firmware on it. Unfortunately, most people would assume a new order should have the latest firmware, if it is two releases back, it may be prudent to ship it with a note to notify buyer to upgrade to the latest firmware. Dave has made some great improvements, and it is a shame not to take full advantage of it.Enjoy your new meter.

author: CDaniel
author_rank: Frequent Contributor
timestamp: July 12, 2019, 05:37:38 pm
content: Is still showing that one random wrong reading but for shorter time so it's not that annoying ... but it is very , very susceptible to the mains electrical noise especially if you hold the probes by hand . This is a problem I never thought possible in a multimeter which is suposed to be near electrical fieldsAs an experiment I injected 1Vpp 50Hz across the DUT resistor and the readings fluctuate houndreds of counts .In a "good" ( every other ) multimeter I have , I can inject even 10Vpp and the reading is stable , maybe is beginning to fluctuate a few counts .Interestingly ( or maybe not ) the high ranges 5M and 50M are allmost immune to the noise , the lower ranges are affected .

author: DaJMasta
author_rank: Super Contributor
timestamp: July 13, 2019, 04:44:55 pm
content: Honestly, I read that as a nonsense test of functionality which shouldn't be expected.The resistance range on a DMM uses a DC current source and measures the voltage that appears as a result of the DUT. Induced noise in the leads is not a big problem because those currents are very small, though at higher DUT resistances, they could present MORE noise in the measurement.Injecting a fixed AC voltage doesn't test noise immunity or accuracy, it just obscures the measurement in a way that will differ with different filtering and method implementations. For example, a meter averaging its resistance range would perform better in such a test than one that reports its measured values quicker. It's also the case that 10Vpp applied to a high resistance load should be manageable to any old signal generator, you can be totally sure your bench signal generator isn't going to be able to maintain 10Vpp in a 5 ohm load or similar... and how much EMI do you have in your lab that you're even getting mA levels of induced current at 50Hz? Are you wrapping your leads around a connected mains cable for every measurement?If you're having issues with measurements fluctuating, it's probably worth looking at the test waveform (with nothing injected) on a scope and looking and consider your measurement techniques because something sounds like it's going very wrong.

author: CDaniel
author_rank: Frequent Contributor
timestamp: July 13, 2019, 05:10:31 pm
content: You have no clue what you talking about ... for example the lack of low pass filtering at the ADC input ( measuring a DC voltage ) is visible if you inject some noise at the frequency of interest ( in this case 50Hz ) . The rest is bullshit , of course I don't inject the noise across a 5ohm resistor , as the induced noise would be anyway very small . I'm talking about "normal" ranges as 500ohm , 5K , 50K , 500K ...And if you don't live in the wilderness 1Vpp noise is very easily optainable ( unfortunatly ) in a lab . A crude way to test it , would be to grab the probes on Vac and see the value displayed .

author: DaJMasta
author_rank: Super Contributor
timestamp: July 13, 2019, 06:07:28 pm
content: Quote from: CDaniel on July 13, 2019, 05:10:31 pmI doubt this will get through to you given the rhetoric so far, but I'll try once with demonstrations.My argument is that even if the instrument has problems with your test case and even if other multimeters are fine with it for whatever reason, it is not a good test of realistically induced noise. So I tested it. For my first test I measured a 750 ohm resistor with the default leads on my 121GW with the positive lead wrapped through several powered up mains cables (60Hz since I'm in the states) and the negative lead wrapped around the mains cable going to a quarter horsepower compressor powered up just before the measurement and still pressurizing its tank - pretty much worst case for mains interference in my lab. I observed not even one least significant digit of fluctuation as well as no movement on the bar graph.Then I put my signal generator at a 50Hz sine wave configured to 10Vpp into a 50 ohm load (the resistor dangling from the leads) and wrapped the positive test probe from the 121GW a dozen turns around the positive lead (not coax and just one side of the load), again I observed no least significant digits of fluctuation and no motion on the bar graph.I don't believe your test represents actual use case conditions outside of extreme EMI environments.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 13, 2019, 07:20:54 pm
content: For a battery powered meter a 1 V AC background during Ohms measurement can be a problem for 2 reasons:One is that it may just run out of voltage to drive the current at some times. The other problem that can also effect other meters is the protection circuit engaging. These may start to become nonlinear at a moderate negative voltage , that is no supposed to be there. Even just 1 V peak to peak is already quite a lot of background, not normally seen, except for really high resistors (e.g. Mohms range).The higher M Ohms range can be tricky in a portable meter due to limited supply voltage. An old meter powered from 9 V may have some advantage here. For high resistance capacitive coupled AC could indeed be a problem. Especially touching a contact could be a problem and should be avoided - more like a user's mistake.Normally the ADC is quite good in suppressing 50/60 Hz main background. For portable meters it's usually combined 50/60 Hz suppression so that no mains frequency detection is needed. The ohms protection and current source may however run into issues here. There are 2 options implementing ohms: one is regulating the current to a preset value and to measure the actual current and voltage. The second method can be better olerating large AC background that can upset the current regulation. If the 2 st method is used, one would ideally get a warning that the reading may not be valid anymore.