A tale of two meters - Page 1
Forum section: electronics / testgear

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 08:37:32 pm
content: The story begins with a post from a member about a new meter they had purchased.QuoteThe original post may be found at:https://www.eevblog.com/forum/testgear/extech-build-quality/In July of 2012 I purchased an Extech EX540 for $300. I still use the meter often and the only problem I've had with it is when I loaned it out to someone who turned the selector past the dead stop and broke the switch. This required some fancy epoxy work but I was able to repair it.I picked up a second one that has a A14 SN compared with my original A10.When I opened the box, everything looked good. Then I turned the meter on.....

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 08:52:20 pm
content: Now keep in mind the old Extech is not a bench beauty queen. It gets used and as such it gets dropped, things get spilled on it, it get's hooked to things that maybe it shouldn't and sometimes people turn the knob past the dead stop.....You can see the lettering has not held up so well. Notice that the new case is also a darker orange. This could be from the sun but the entire case of the old meter is lighter.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 08:54:53 pm
content: Notice how the case has cracked on the older meter where the probes are stored. Wait, there's a new sticker too.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:00:02 pm
content: Getting back to turning it on for the first time. Well, as I turned the selector switch, the meter turned off. Then it reset. I played with it a little and the selector was really intermittent. I had never had any problems with the old meter's switch until I loaned it out...But wait, does that old meter have a blueish tin to the LCD?? The new one looks more black.What you can't see in the picture is how the back light is flickering on the new one where the old one is nice and solid. On the plus side, it's not singing...

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:05:16 pm
content: I've had my old meter apart before and was not too concerned with turning the meter for warranty. So out comes the screw driver and as I went to remove the battery cover I noticed this small difference... A little advertisement did not concern me too much.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:08:52 pm
content: While I was removing the screws which have a washer and an O-ring on each, I noticed one of the O-rings was missing. I looked in the hole and somehow it had been wedged down in there. Not a big deal. But then I look at the cover.... Something strange. There is a spring on the PCB that would normally attach to a shield but there is no shield.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:10:52 pm
content: Maybe it was left off by mistake. Maybe it was a design change. I wrote Extech and asked. In the mean time, I broke out some copper foil.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:17:05 pm
content: To be honest, the missing shield was not the first thing I noticed. What I noticed first was how the metal shield that covers the sensitive area looked like it had been forged with a rubber mallet. The old meter is bent nice and cleanly.You may also note some of the other differences. The old PCB has a deep gold tin to it compared to the new. At least they cleaned up that botched part.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:29:59 pm
content: Where was I going with this, oh yea, the meter does not turn on.. I was also seeing strange things like the meter would not read the correct resistance. Let's see what's going on with that switch.Sorry for the poor quality picture. There are six contacts, five of which are the same. One is wider than the others, shown on the right. It's resting height is much lower than the others. I took out my trusty X-acto and shaved a very small amount off the ends of the plastic so it's resting height was the same as the others. I also removed any burs I saw and made sure none of the contacts were hanging up.Looking at the rest of the plastic, I was reminded just how weak this area is. IMO, this is a very poor design. On the old meter, the hex insert split and half broke off. I found an inverted star washer that press fit over the shaft, then epoxied the whole thing up. Sanded the plastic first (learned from the first switch). If this breaks, it's taking the shaft on the switch with it!

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:39:37 pm
content: So the switch is all apart and I am playing with the old meter while I wait for the epoxy to dry. I was thinking for a water sealed setup, this really has a nice feel to it. I pick of the new meter and turn it. Keep in mind there is no switch. It's tight. REALLY tight!!! So I decide to take the dial off of the new meter to see what's going on. I look at the C-clip and rather than fitting into the grove it is smashed around the shaft.I spent some time with the Dremel next grinding that C-clip to about 1/3 of it's thickness. I then honed the flat side and rounded the edges. Yes, finding a better C-clip may have been an option as well.... I cleaned all the parts up and greased them. The clip fits as it should now and the dial is much smoother. Snug, but smooth....The end of the clip did not fit inside the groove before. It was bad.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 09:49:01 pm
content: Crazy EX540 with your 6 MOVs, 3 PTCs and 3 HV resistors. Where do you fit all this stuff? Quick answer, you don't....The workmanship in this area was poor. Clearance, we don't need no stinking clearance! The leads on one PTC were really close to an area that they should not be near.. Extech, you want these meters to survive don't you?Solder, bend, heat shrink....The one thing I never liked about this meter was that ground return. All the current flowing in that massive loop. The MOV's return path is so close, yet so far away......

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 11:08:09 pm
content: The PCB appears to be a few revisions newer. Note the diode near the - battery connection on the older meter.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 10, 2016, 11:11:22 pm
content: How much does a star washer cost anyway?? The new meter was missing the two washers for the common and uA/mA studs. These were there on the older version.

author: janoc
author_rank: Super Contributor
timestamp: June 10, 2016, 11:28:00 pm
content: I have an Extech 470 which has also similar problems - the range switch is intermittent, the meter often shows random nonsense on the LCD or just locks up. The original seller has actually sent me another 470 free of charge, which was working.You will find quite a few posts on the forum that Extech has quality control problems, some meter series are good and some are just junk, even for the same models. They are probably changing factories where the meters are assembled or something. I have sold my working 470 recently and not planning to get another Extech. Not worth the money, IMHO. You can get a much better Brymen meter for that price.

author: AF6LJ
author_rank: Unknown
timestamp: June 10, 2016, 11:39:06 pm
content: WoooNot Good, I have to wonder if that is one of those non authorized (midnight manufacturing CO) meters.

author: Lightages
author_rank: Unknown
timestamp: June 10, 2016, 11:52:31 pm
content: This is what most people complain about with the Extech meters made by CEM. The quality is all over the place..

author: joeqsmith
author_rank: Super Contributor
timestamp: June 11, 2016, 12:12:08 am
content: Extech supplied the alignment procedure for the meter and I verified it. They do not have adjustments for the DCA, capacitance or resistance. The meter is well within spec but the DCA could be a little tighter IMO.So the switch works very well now. Not real happy with the flicker but it's tolerable.Attached 1mV and 10V with the two EX540s compared with the BM869s and UT181A.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 11, 2016, 12:43:40 am
content: Missed a couple. Note the flat vs round shunt. White glob on xtal vs solder. Axial resistor under fuse. I also cleaned up the soldering (shunt, fuse holders, protection.....) and cut off the excess leads. Wonder how they crushed that can. At least they are still using SIBA fuses.I do like the meter overall but the $300 price tag, I expect it to be much higher quality. It does have an RF link and it actually works. You can talk to the meter with Labview. Personally, of all the meters I have looked at I still like the BM869s best for a portable bench meter.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 11, 2016, 12:58:44 am
content: You should have a look at the contacts. Maybe a little trimming with a razor blade would solve it. This one is now rock solid.It was really strange how it acted. The meter would turn off at times. Or it would change modes, which I assume was a reset. In ohms, it would read a short as 0, but it would read 50 ohms as 0. 1K as 0. 10M would read 10M, most of the time. Cap mode was the same except it would reset at times bask to ohms. Brand new, seems like it would never have made it out of the factory.Quote from: janoc on June 10, 2016, 11:28:00 pm

author: janoc
author_rank: Super Contributor
timestamp: June 11, 2016, 01:49:31 pm
content: Quote from: joeqsmith on June 11, 2016, 12:58:44 amI had it open a few times already, the switch looks ok visually, so not sure what the deal is. I will try to check it again, thanks for the tip.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 14, 2016, 03:13:04 am
content: I did hear back from Extech who offered to repair the meter. I will say I have been very pleased with their communications. I provided them with a link to this thread.I almost forgot... I had not played around with the back light a whole lot after going over the meter. I was planning to make a video with the high speed camera showing the flicker. Looking at it very carefully I can no longer see any sort of flicker. I suspect this was also caused by the intermittent selector switch. It makes sense as the power would shut down.

author: jitter
author_rank: Frequent Contributor
timestamp: June 14, 2016, 07:45:50 am
content: Thanks for this comparison and the solutions, it may benefit others out here that have these meters.I would concur with you that the little differences between the old and the new meter you're describing are indeed the result of revision changes. Changes to fix oversights.The bigger issues, mainly the mechanical misfits, seem to me to be more like the result of changing suppliers.I've been working on a metrology grade instrument for over 10 years now, and at first we assembled everything in house. By now most modules have been outsourced to a plant the company I work for owns in Eastern Europe. They have very good quality control but when they had just started making them I saw all the little things we did wrong at first reoccur, until they learned about them too.Hopefully, with your Extech it's a similar thing and they get QC in place again, or otherwise it doesn't bode well for them.I have an EX830 that I posted ateardownof only yesterday. Based on what I found I had already decided that the chance of me buying another Extech was rather slim, and your thread reinforced that feeling.One thing that also plays a role is the price. This meter cost me € 160 in 2007. It's still available now, but today they want about € 250 for it...Perhaps at the time the brand was new over here and they were selling it under the market value to get a foothold.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 14, 2016, 11:48:41 am
content: Possible.When my wife saw it the first thing she said is it looked like a used meter that someone had attempted to repair it and resold as new. That's also possible. Maybe it was a demo unit, which could explain the bent metal can and missing washers. We could make up all sorts of stories but really I have no way of knowing.There are only a couple of video reviews of this meter. This one shows how to measure the temperature of your AC line.https://youtu.be/lFkgyQEq_Jo?t=62This one shows how the metal can may have been bent.https://youtu.be/zJpqbkoOGgE?t=84I thought about doing one but with so many mods to the meter, I suspect it would bias the results.Quote from: jitter on June 14, 2016, 07:45:50 am

author: jitter
author_rank: Frequent Contributor
timestamp: June 14, 2016, 01:52:17 pm
content: Quote from: joeqsmith on June 14, 2016, 11:48:41 amYour first EX540 has revision 5 on the pcb and your second is already up to 9.To me it seems most likely that the "bodges" that were put on the "5" to solve some issues found their way into the layout of the subsequent versions.I say this because my work is mostly on that instrument I wrote about in my previous post. It's a bit of a niche instrument, so you're talking about 500 a year, worldwide.With those low numbers, some "bodges" (fixes) may remain in the design quite long as redesigning and respinning boards just isn't cost effective. Often they wait until a number of mods can be put in the redesign all at once.And if the mod is considered of high priority, we still get to modify and use up existing stock which may be 100, 200 boards tops.This Extech would no doubt sell more, so they just use up old stock, modify them and then redesign the boards with a newer version for the next batch.QuoteThat guy looks like he poked his own fingers in an outlet one time too often.QuoteMaybe they did that to your first meter, buffed it up and sold it to you ("like a bought one" Dave would say).

author: joeqsmith
author_rank: Super Contributor
timestamp: June 14, 2016, 11:04:30 pm
content: Let's assume there were 5 revisions, or 4 after my original meter. Now lets look at what changed with the PCB. The plating. There's one rev. That gives us three revs to fix the tacked on diode bodge.I'm sure there were other changes.Quote from: jitter on June 14, 2016, 01:52:17 pm

author: jitter
author_rank: Frequent Contributor
timestamp: June 15, 2016, 07:39:45 am
content: Now you're assuming that a revision change only incorporates one component, but often there are multiple. I have also seen that not all revision changes actually make it into production. And sometimes a change in firmare is all it takes to change revision, so unless you keep track of all the changes, there's no way to know for sure what changed when (and why).

author: joeqsmith
author_rank: Super Contributor
timestamp: June 15, 2016, 11:26:35 am
content: Quote from: jitter on June 15, 2016, 07:39:45 amAssuming? I have the two products sitting side by side and am not concerned with taking my chances with the self tappers. Your comment of "bodges" is why I directed my comment to the diode. I guess the axial leaded trim resistors are somewhat of a bodge but both meters use this technique and the board does not appear to be revised to improve their bodgeability.Obviously changes can require revisions to the board.I would assume any changes they made were for profit. Then again we do have Dilbert.Quote from: jitter on June 14, 2016, 01:52:17 pm

author: jitter
author_rank: Frequent Contributor
timestamp: June 15, 2016, 04:44:51 pm
content: Quote from: joeqsmith on June 15, 2016, 11:26:35 amPlease don't. As you don't have board revisions 6, 7 or 8, you have no way of finding out what modifications/bodges went into the layout and in which revision.Quote"Bodge" would not be the technical term used by a manufacturer, "fix" or "modification" sounds a bit better...QuoteAny bodge that needs to be put in by hand is way more expensive than when a PNP machine can do that in a correct layout. So yes, cost is a big factor in that, but may only be done if the cost of changing the layout outweighs the cost of modifying by hand. In large production runs, that will be the case.We also see that some manufacturers change a layout whatever the cost. Sometimes they get to deal with customers that tear down an expensive piece of equipment (sound familiar?) and ask questions why there's a bodge on a board. This won't be your typical consumer, but in industrial electronics, it happens, and protecting a good name can be all that's necessary...

author: joeqsmith
author_rank: Super Contributor
timestamp: June 15, 2016, 05:18:44 pm
content: Don't? Don't what?You are correct, I have two meters rev 5 & 9. That's perceptive!The bodge on the old meter that was corrected (or forgotten) was the tacked on diode. Indeed I have no need or desire to see the other revisions. This meter was bad enough.I did not choose the wording. I do not know if fixes drove the revisions. Some of it may have been part obsolescence but I don't refer to those as bodges or fixes.I wonder if the new behavior seen in next post is a result of a bodge.Reputation, manual rework, everything boils down to making a profit. Well, if a company want's to remain profitable.Quote from: jitter on June 15, 2016, 04:44:51 pm

author: joeqsmith
author_rank: Super Contributor
timestamp: June 15, 2016, 05:38:41 pm
content: After the new meter was reassembled, I noticed it behaves strange in the CV mode. I made a short video showing the difference.

author: jitter
author_rank: Frequent Contributor
timestamp: June 15, 2016, 07:15:08 pm
content: Quote from: joeqsmith on June 15, 2016, 05:18:44 pmDon't take them apart again. If the self tappers are as bad as on my EX830, then the next disassembly might ruin what's left of the thread in the plastic.QuoteObsolecence seems unlikely for stuff like resistors, capacitors, or generic diodes.QuoteCan you check the link? It doesn't work for me.Edit: I got to it through the link in your signature:QuoteYes, indeed.

author: jitter
author_rank: Frequent Contributor
timestamp: June 15, 2016, 07:24:51 pm
content: It's not the exact same behaviour, but my recently calibrated Agilent U1232A doesn't go all the way down to 0 V either in the AC range. Even with the input shorted it stays at 1.9 mV.The EX830 will drop down to 0.6 mV when the input is shorted.

author: timofonic
author_rank: Frequent Contributor
timestamp: June 15, 2016, 08:50:17 pm
content: Soon it will be safer to design your own DMM than buying one.Those will be great times for Open Hardware

author: joeqsmith
author_rank: Super Contributor
timestamp: June 16, 2016, 12:37:00 am
content: That was a link to the edited video.. Thanks for adding the correct link. That meter is all over the place and that 20ish seconds seems timed by software. Why is samples and stays at zero, remove the 50 ohm and it drift up even higher than the 1mV, then reinstall and it has no effect.Maybe this is by design. Almost wish I had another one that was blessed at the factory as a golden unit.You know, I have never had much of a problem with self tapping screws. They are used everywhere. I just turn them backwards to make sure they drive into the threads the same.Hey Timofonic, I will leave that one up to Dave for now. I am very interested in seeing how the fat boy, which should be the new standard to judge all meters by, compares with the rest of the pack.Quote from: timofonic on June 15, 2016, 08:50:17 pm

author: Cristiano
author_rank: Newbie
timestamp: June 16, 2016, 09:24:52 am
content: Quote from: joeqsmith on June 14, 2016, 11:04:30 pmHi Joe;My EX540 also have a big drift in Vca and mV!!!! I didn't have time of test very well this multimeter, but when saw your video I checked the my.videos:Vac -https://www.dropbox.com/s/rc43stuxq34myva/V_20160615_204907.mp4?dl=0mV -https://www.dropbox.com/s/ck28hlfkq095tms/V_20160615_205940.mp4?dl=0I sent email and videos for EXTECH yesterday. I am waiting response....Thanks

author: joeqsmith
author_rank: Super Contributor
timestamp: June 16, 2016, 11:41:18 am
content: Thanks! So that delay I see prior to the ACV starting to drift happens on multiple meters. Mine is a A140 SN.After watching your videos with the leads removed, I tried one more test and then stumbled onto another difference between the two meters. This would be a very easy test for you to try as well and may help Extech solve their problem if they decide it is worth going after.Quote from: Cristiano on June 16, 2016, 09:24:52 am

author: joeqsmith
author_rank: Super Contributor
timestamp: June 16, 2016, 02:19:52 pm
content: Pulled the can to have a look and straightened it out a bit. Fits nice. Can't see why it was so mangled to begin with.IC3 uses the TI logo and is a TL052. IC9 is an AD6363 but does not appear to be an Analog Devices part. It has a CJ logo. Nice how the large device, IC2, is not marked.I'll spend a little time and see if I can sort out what the problem is.

author: jitter
author_rank: Frequent Contributor
timestamp: June 16, 2016, 02:29:41 pm
content: No markings on an IC, as in "it was never there, not even sanded off"?Funny, there are two positions called R62. Both look to be hand soldered. Perhaps placed during testing to pull some spec within tolerances?

author: joeqsmith
author_rank: Super Contributor
timestamp: June 16, 2016, 02:53:23 pm
content: More interesting is that the Analog Devices data sheet shows a minimum of 5V for single supply operation. I am seeing 2.738. Looks like I need to have a look at the working meter.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 17, 2016, 02:03:57 pm
content: Spent a little time with the AD636 datasheet. I did not realize is used a split supply. Rechecking and its 5.460.I removed the can from the old meter. Noticed C22 polarity was not the same. Powering up the meters, it appears like it was placed backwards on the old meter but they corrected it on the new one. The older meter's RMS converter was a Cyrustek ES636 rather than the CJ part used on the new one. IC2 was marked on the old meter. It is a Cyrustek ES51966P. Datasheet is on-line for it.There appear to be some changes to the artwork and design in the analog area. A transistor was added, some pads for a resistor that is not populated.... No schematic and may need to trace it out.However, looking at the AD636 pin 6 relative to pin 10 with the inputs of the meter shorted, it will begin to drift after some time. I strapped pin 1 to 10, and it will still drift. Looking at the old meter between 6 & 10 with the inputs to the meter shorted, it remains steady. So at least the problem appears to be with the RMS conversion stage. I may start with this CJ part. Looks like there are a few differences between the Cyrustek and the Analog Devices part.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 18, 2016, 01:49:18 am
content: Shown with C22 polarity change between two meters. Again, the new meter is correct.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 18, 2016, 01:53:41 am
content: While there are many changes to the design, after tracing out the RMS stage, it appears very similar if not identical. To be honest, I am not sure what they are doing after reading the data sheet. I'm to the point I would like to swap out that CJ part but can't find an a source. AD does not appear to make one in an SOIC. It really would be a bodge.

author: retiredcaps
author_rank: Super Contributor
timestamp: June 18, 2016, 02:10:02 am
content: Quote from: joeqsmith on June 18, 2016, 01:53:41 am$16.21 from aliexpress and probably 2 months to ship. My aliexpress orders are taking almost 2 months to arrive to Canada.http://www.aliexpress.com/item/spot-IC-CJ-AD636-IGTA1JD09EL-special-Electronic/32642668777.html

author: joeqsmith
author_rank: Super Contributor
timestamp: June 18, 2016, 02:57:50 am
content: Thanks but I actually want the ES636 from Cyrustek that is on my original meter. I may try and find the 16-pin SOIC version.Quote from: retiredcaps on June 18, 2016, 02:10:02 am

author: joeqsmith
author_rank: Super Contributor
timestamp: November 02, 2016, 01:35:10 am
content: QuoteYea, I'm sure....So after all this time, I drop in a new RMS converter into the brand new EX540 and aligned it. As much as I would like to report that the meter now works as good as my original, sadly it does not. If you own a later SN and were planning to try the swap, don't waste your time. There is still one or more other changes that are causing some of the problems I am seeing with it.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 27, 2016, 10:55:08 pm
content: Someone was asking about a twin display meter and I mentioned the EX540 having an RF link.https://www.eevblog.com/forum/testgear/twin-remote-display-multimeter/I thought, I should try that out and make sure it really works with Windows 10. I plug in the adapter for the first time and the PC did nothing. I found drivers for Windows 10, installed them. Tried the adapter again, nothing.Look at the adapter "brand new" purchased from a major distributor and I notice two of the three screws holding the adapter together are missing! I take the third one out and pop the cover. Thread marks where the screws had been inserted at one time. Would be fun to know the history of this meter.Looking at the adapter, first someone had really mangled where the wires attached to the PCB. Someone had twisted things enough to fray much of the wiring. I cleaned all this up and applied new hot glue. Looking on the top side, noticed one joint for one of the ICs had not wicked to the lead. Cleaned up some of the soldering and tried it out.The PC now finds the adapter. Run their software, turn on the meter and enable the link. Nothing.....Decide I better just start with my old meter and adapter that I know works. Sure enough, everything still works. I then turn on my new meter with the old adapter. Nothing. Old meter with new adapter, works.EX540 comes back apart....Remember how the new meter was missing the shield on the back cover and I cut a new on out of some foil? Well there were some leads on the RF board that made contact with the foil because they had not trimmed them. Is this why they did not install the shield? Trim the leads, double check the soldering and tried it out. Both meters now work with both adapters.Was the meter sold, the RF did not work and an unskilled person attempted to repair it? Was it just returned and the distributor attempted to repair it? CEM knowing shipped it defective with missing screws?Crazy how different these two meters have been...

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 27, 2016, 12:06:09 pm
content: Just a question about graph bar, joeqsmith: it is really updating only with the value and not faster?

author: joeqsmith
author_rank: Super Contributor
timestamp: December 27, 2016, 03:25:18 pm
content: Quote from: 3nigm4 on December 27, 2016, 12:06:09 pmThe EX540 has the worse bar graph of any meter I have looked at. Watch where I compare it with the TPI 194II, the Brymen BM869s and the UNI-T UT181A.https://youtu.be/fkf0V3Xvq_w?t=1307

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 27, 2016, 08:00:52 pm
content: Definitely unusableI see an offer for a CEM DT-9939 for 160€ shipped... but I think is better to wait a bit.Seems that the UT181A has all I need, except price

author: joeqsmith
author_rank: Super Contributor
timestamp: December 27, 2016, 08:34:45 pm
content: I personally like the 181A. The things you may want to consider are that the LCD lens is easily scratched. You can't use the meter while it is charging and I am not aware of them offering a spare battery. They claim 40 hours of run time and the two times I have charged it, it sat overnight. The charger does not come with any AC plug adapters. Not certified to meet the EMC standards, or the safety standards for that matter. While the meter may very well be "safe" it is not very robust and easily damaged (like most UNI-T meters I have looked at). If you watched the video how I attempted to harden the UT61E, I had a couple of cuts in the PCB to add a few parts. Improving the UT181A was not so simple. It really needs a new rev of the circuit board.On the plus side, it basically drives like a Fluke 289. They actually used some decent parts, at least in the one I have. It is the most temperature stable meter I have looked at. I have not owned it long enough to say anything about the long term drift but so far it seems to be well within calibration. Of the meters in that video, I still would hands down take the Brymen BM869s.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 27, 2016, 09:11:01 pm
content: What I don't like about brymen is the limited frequency counter.... only 1 MHzI also found good for me the Amprobe AM570 in the same price segment, with less features than brumen but 60 MHz and no PC connectionI'll continue my researchThank you for your videos, i watched about allvery informative

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 27, 2016, 09:26:15 pm
content: How do you compare the EX540 to U71x series? I see that both share the same controller, the ES51966. Th main difference is the MCU, where di Extech/CEM use the Atmel ATMEGA32 and UT71x the TI MSP430.I feel like the Extech is best designed but with cheaper components.If you have to choose between them, witch one you will pick?

author: joeqsmith
author_rank: Super Contributor
timestamp: December 27, 2016, 11:17:08 pm
content: I have never looked at any of the UNI-T UT71's so I have no way to compare them beyond what is in the manuals. Typically I see glass fuses inside only the poorest of the meters and was surprised to see them.It's pretty rare I need to measure frequency with a handheld for the reasons I mentioned earlier. You are correct that the manual for the BM869s shows for logic levels, the frequency range is 5Hz to 1MHz. In the AC line they list a maximum of 200KHz. And I am sure that they all meet this standard. However, consider the attached two pictures.While I am not a fan of the UT61E, I think it was able to read the highest frequencies of all the meters I have looked at so far. They are not a lot of money here. Personally, the lack of a backlight and the fact that I could damage it so easily, I would have no need for one. They do come with the cable to log data. Some charge extra for this.After watching some of my videos, you know I typically run them to failure using a common test. The EX540 I have (even thought it's new) has been changed so much it would not be a good indicator of how a stock one would perform against the other meters.If I had to choose I would take my older 540. The quality of the new one really suffered.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 28, 2016, 03:42:09 am
content: You may have noticed my scribble marks on the amplifier was 400KHz to 14MHz.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 28, 2016, 05:09:05 am
content: The scope, like the meters is not real good for a counter. The first picture is with my old HP RF generator which I am using to drive the amplifiers. The second picture was using my Marconi generator without an amplifier terminated to my old HP counter. Both RF generators and the counters are referenced to a GPS that runs 24/7. I was actually surprised that the Brymen was this tight.While I did damage this meter during my transient testing, I did not change anything in the design during my repairs. I would expect another BM869s would behave much the same but we are running it way outside of their specs so you never know.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 28, 2016, 06:11:21 am
content: And just so you have some sort of accuracy data to go with it. I have never attempted to adjust the clock reference for any of these meters.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 28, 2016, 10:59:39 am
content: Thank you joeqsmith for allI did not think were possible to reach such frequencies with that meter. From the cheap seller I can take it for about 240€ shipped without USB cable... I'll take a bit of time to think

author: joeqsmith
author_rank: Super Contributor
timestamp: December 28, 2016, 06:38:11 pm
content: No problem. Glad to help.Most of my test equipment I bought used. This is one of the Fluke 97 scopemeters I found locally. They were a little rough from a garage life but working for the most part. The meter function reads to about 5MHz on this one and the scope you can see is much worse.I would guess you could get a good counter for little money and then focus on some of the more important functions you may want the meter for.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 29, 2016, 02:02:57 pm
content: I am also thinking to buy a Brymen and build a prescaler for fast TTL frequency check.Another question about EX540: I see that it uses an AD636 but from your pictures I'm not able to see if it has also a voltage reference IC somewhere

author: joeqsmith
author_rank: Super Contributor
timestamp: December 30, 2016, 01:40:24 am
content: If you watched that video I made where I attempted to improve the temperature drift of the UR61E, you will notice that the EX540 had the worst drift of the meters I have tested. I'm sure they use a reference, but I have never had a reason to dig into what they used. The AD636 is some knockoff part.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 30, 2016, 10:13:00 am
content: Quote from: joeqsmith on December 30, 2016, 01:40:24 amYes, the True RMS converter.I'm keeping to thing about it 'cause lately the prices here in EU is raising fast... maybe due to the USD running close to EUR (today 1€ = 1.058$... while a year ago ~1.20$ and 10 years ago ~1.60$).. at the moment:- Uni Trend UT181A (60MHz, USB adapter included, ES51997+Cortex 32bit+TFT): 270~350€- Brymen BM869s (1MHz): 219€ (259€ with USB adapter)- Uni Trend UT71D (400MHz, USB adapter included, ES51966+MSP430): 173€ (130€ non GS/TÜV approved)- Brymen BM867s (1MHz, no temperature): 159€ (219€ with USB adapter)- Amprobe AM-550 (60MHz, 6000 count, no PC connection): 158€- CEM DT 9939 (100MHz, USB adapter included, slow display, ES51966+ATMEGA32): 155€- Brymen BM829s (1MHz): 150€ (190€ with USB adapter)- Uni Trend UT71C (400MHz, USB adapter included, ES51966+MSP430): 148€- Uni Trend UT61E (220MHz, USB adapter included, no temperature, ES51922): 87€- Uni Trend UT139C (10MHz, no PC connection, DTM0660): 40€

author: joeqsmith
author_rank: Super Contributor
timestamp: December 31, 2016, 03:56:41 am
content: I had swapped out the 636 on mine to see if it was the cause of one of the problems. It wasn't. Lost interest in it. You spend over $100 on a meter, you would think it would work right out of the box and it would be as good or better than the exact same model purchased a few years prior. There are some odd ball brands of this same meter on Amazon for 1/3 the price of the rebranded Extech. That would be a fair price but I wonder if they cheapen it up even further.

author: .rpv
author_rank: Contributor
timestamp: December 31, 2016, 10:08:01 pm
content: Quote from: 3nigm4 on December 30, 2016, 10:13:00 amthe 61e includes a RS232 adapter, not usb, I tried with a RS232 to usb adapter and didn't work.

author: 3nigm4
author_rank: Regular Contributor
timestamp: December 31, 2016, 10:21:27 pm
content: Quote from: .rpv on December 31, 2016, 10:08:01 pmNot the EU version sold by some german seller. The whole UT61x series there is sold with USB cable

author: .rpv
author_rank: Contributor
timestamp: December 31, 2016, 10:32:05 pm
content: Quote from: 3nigm4 on December 31, 2016, 10:21:27 pmOh!, I didn't knew, that's a very nice add, RS232 is just

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 02, 2017, 07:47:45 am
content: Quote from: .rpv on December 31, 2016, 10:32:05 pmYep! That's absurd in 2016.. ops, 2017 that something is sold with a so old connection

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 03, 2017, 07:57:33 am
content: Quote from: joeqsmith on January 03, 2017, 01:08:40 amI couldn't wait and ordered one me tooI'm excited to see your job

author: IanB
author_rank: Super Contributor
timestamp: January 03, 2017, 08:07:36 am
content: Quote from: .rpv on December 31, 2016, 10:32:05 pmDo meters with a USB connection create a virtual serial port on the host computer? For me the advantage of RS232 is that I can directly access the meter comms and write my own logging software. If there is no comm port to access this becomes much more difficult.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 03, 2017, 01:17:38 pm
content: QuoteAll the ones I have looked at do, including this meter.Quote from: 3nigm4 on January 03, 2017, 07:57:33 amI never heard of the place I ordered mine from. Even their ad shows the meter with two different colors. One CEM blue, the other Fluke yellow. They do not say if they use the 400 or 900 MHz radio. It's a total grab bag! But it's so cheap, we just have to have a look. It will be funny if this meter actually turns out good. They show it meeting the standards so they shouldn't have pulled the HRC fuses and replaced them with glass. 40,000 count, tri-display, AC-DC and an RF link for $100, what could go wrong!? Post pictures of yours when you get it. This is a link to the ad of the one I have on order.http://www.ebay.com/itm/DT-9939-Waterproof-Industrial-Wireless-USB-RMS-Multimeter-Capacitance-Frequency/132045551020?_trksid=p2141725.c100338.m3726&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20150313114020%26meid%3Df8991ab2c3064b60bcbce643365f4625%26pid%3D100338%26rk%3D1%26rkt%3D4%26sd%3D181215338698

author: ProBang2
author_rank: Frequent Contributor
timestamp: January 03, 2017, 02:19:05 pm
content: I hope you get the blue one (but I doubt). It is authorized for the european market.Impressive: It is still rated as Cat IV 600V / Cat III 1000V (different to the downrated UT61E).And there is theCertificate...

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 03, 2017, 02:24:33 pm
content: Quote from: joeqsmith on January 03, 2017, 01:17:38 pmOf course I'll post themIn the meantime, this is minehttps://www.reichelt.de/Digital-Multimeters/CEM-DT-9939/3/index.html?ACTION=3&LA=446&ARTICLE=134762&GROUPID=4058&artnr=CEM+DT-9939&SEARCH=dt9939

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 03, 2017, 02:41:03 pm
content: Quote from: joeqsmith on January 03, 2017, 01:17:38 pmI prefer the Yellow one, but it seams only sold in USA (the one you bought) or the one rebranded Jaycar QM1575Your should be the 915 MHz (USA version), that is like the EX540Quote from: joeqsmith on January 03, 2017, 01:17:38 pmI'm confident, we just have to waitEdit: this is a picture from mjlorton forumhttp://www.mjlorton.com/forum/index.php?action=dlattach;topic=191.0;attach=3016;image

author: joeqsmith
author_rank: Super Contributor
timestamp: January 04, 2017, 12:12:07 am
content: Looks like it has been shipped and due to arrive this week. It looks like the blue one you linked costs more than the one I have coming. It will be interesting to see if yours and mine have the same problems my last EX540 has. If the new meter works, I may have to take some time and really dig into what is going on with the 540.

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 04, 2017, 06:26:05 am
content: Quote from: joeqsmith on January 04, 2017, 12:12:07 amYes, and is the lowest price I've found here... even the one you bought, imported here with taxes and duties will cost me about 200€

author: joeqsmith
author_rank: Super Contributor
timestamp: January 04, 2017, 07:08:55 am
content: Well, you hopefully won't get the glass fuses like you saw with your last crap meter. Then these should actually pass the EMC standards, which while I never tested the UNI-T you had, I would bet it would fail on that grill starter test. Having it certified is a big deal. For $100, my expectations are pretty low.What would the Extech branded one cost? Where I bought mine from, it was $300.http://www.testequipmentdepot.com/extech/multimeters/industrial-true-rms-digital-multimeters/true-rms-industrial-multimeter-datalogger-1000v-20a-wireless-pc-interface-ex540.htm

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 04, 2017, 07:50:57 am
content: Quote from: joeqsmith on January 04, 2017, 07:08:55 amThe rebranded EX542, cost 302€... twice the CEM pricehttp://www.tme.eu/it/details/ex542/multimetri-digitali-portatili/extech/

author: joeqsmith
author_rank: Super Contributor
timestamp: January 07, 2017, 12:42:43 am
content: Mine made it in. Branded CEM, blue TUV and GS cert. I thought it may not be use 915MHz but it appears the software is the same between the two meters. Both meters work with both adapters. I never tried it until now but the software handle two meters logging to it at the same time.A $300 meter for $100. At a glance, it looks legit. So what gives?I was going to run an analog meter next but I am really curious about this thing. Let me know what you end up with.

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 07, 2017, 06:29:18 am
content: Mine is currently waiting at the local courier depot 'cause yesterday was an holyday... I don't think to wait until monday... if this morning they are open I'll go picking itEdit: I abandoned the idea... it's an odyssey tring to contact DHL (toll number) to know if the local office is open

author: joeqsmith
author_rank: Super Contributor
timestamp: January 08, 2017, 12:25:17 am
content: No problem. I spent the day working on a review for it. I keep thinking this meter cost less than the Hioki DT4252, the Fluke 115 and the EEVBLOG rebranded Brymen BM235 with much higher performance and it was independently certified. Of course, it may fail the grill starter test like so many UNI-Ts....I still need to run the continuity test, pull the thing apart and run the HV test on it before starting the destructive tests. I may hold off the destructive tests until you receive yours. If you end up with a problem, at least we could compare results.

author: evava
author_rank: Regular Contributor
timestamp: January 08, 2017, 08:19:38 am
content: Joe, would you be so kind and try overloading this meter with AC volts on DC range, and with DC volts on AC range, like in this thread?https://www.eevblog.com/forum/testgear/brymen-multimeters-fault/75/And please, continuity is? (very slow, slow, fast, very fast ?)Thank you.

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 08, 2017, 12:32:54 pm
content: Quote from: joeqsmith on January 08, 2017, 12:25:17 amI hope for a better result... but the grill starter... is the grill starterQuote from: joeqsmith on January 08, 2017, 12:25:17 amTomorrow I'll get it and give it a try... in the meantime, don't be too harsh with it, poor baby

author: joeqsmith
author_rank: Super Contributor
timestamp: January 08, 2017, 01:49:32 pm
content: Quote from: evava on January 08, 2017, 08:19:38 amGood idea. No problem, I'll add it to that thread.I have ran my normal continuity test and have updated the spreadsheet with that data.https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat

author: joeqsmith
author_rank: Super Contributor
timestamp: January 08, 2017, 02:20:51 pm
content: Quote from: 3nigm4 on January 08, 2017, 12:32:54 pmI finished up the HV tests last night. I just need to pull it apart and see what's inside. I'll run the transient tests no matter what I find.Rather than a 2 part where I show the transients separate, I may just wait and put it all in one video. So depending how your meter works out, I may not post the video for another week. Personally, I am really curious how this thing stacks up. At $120 it could end up being a great deal (until I find the glass fuses inside)!

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 09, 2017, 07:38:34 pm
content: Tested various functions, seems to be ok, even the PC connection... let's go with the grill starter

author: joeqsmith
author_rank: Super Contributor
timestamp: January 09, 2017, 11:13:12 pm
content: Looks like you have the same meter. Post the first 4 or 5 digits of the SN#. Did you check your RF link too?

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 09, 2017, 11:32:50 pm
content: A few picturesThe serial number starts with 141200...Mine has also the floating/raising value while repeatedly turning light on/off; but is not a backlight issue: in my case it's related to buzzer... if I turn off the beep in settings, the value stays stable.And yes, the RF module works fine

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 09, 2017, 11:34:34 pm
content: And one fix: the shield was bent and not soldered in one side.Added also a bit of tubes on resistors.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 10, 2017, 12:33:35 am
content: QuoteMine is 130519... Sounds like if you are putting heat shrink over parts and correcting the soldering, you're keeping it. For the price, it's a pretty good meter.I'll warm up the grill starter... Can it beat the Fluke 87V? I have low expectations....

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 10, 2017, 06:14:29 am
content: The RMS converter is an AD636 marked CJThe case is marked 11/14 so it is built november 2014 and seems that the serial number match that periodEdit: there is no shielding on the back caseEdit2:Quote from: joeqsmith on January 10, 2017, 01:48:30 amIf you look at picture picture 7, there is a normal resistor in place af an SMD version soldered in on the near component

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 10, 2017, 01:21:41 pm
content: First picture, under the fuse; second picture, added back shield with a free zone around the RF antenna

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 10, 2017, 03:48:14 pm
content: Watched your video and it seems that the meter defends wellFor the backlight on/off AC issue, as I said previously, try to disable beep in setup: in my case it stopped raising the AC voltage

author: joeqsmith
author_rank: Super Contributor
timestamp: January 10, 2017, 05:56:36 pm
content: For $120, hard to knock it. Was glad I finally was able to run one.I turned off both the Extech and CEM's phonating function. I then left the meters on for 1 minute. I then pressed the pressed the crap out of the BL buttons. Both meters did the same thing, no effect. So yes, it appears the problem is tied to the beeper.With yours having a CJ part and higher SN, I suspect it will run to a lower voltage. I did not check mine but that new Extech will run the battery into the ground before it stops working.

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 10, 2017, 09:33:56 pm
content: Quote from: joeqsmith on January 10, 2017, 05:56:36 pmI'll give it a try in next days

author: joeqsmith
author_rank: Super Contributor
timestamp: January 10, 2017, 11:24:00 pm
content: I thought the one thing that would have gotten your attention was the 150MHz frequency counter.My CEM will turn on the Low Battery at 6.98 volts but will run down to about 4.6 volts. Current draw @ 9 volts is about 4.8mA. With back light and RF about 36 mA peak (when sending data).

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 11, 2017, 08:06:35 am
content: Quote from: joeqsmith on January 10, 2017, 11:24:00 pmYep! Enough for my needs at the momentThank you for the video and for all the testing... and to reveal its physical limits

author: SeanB
author_rank: Super Contributor
timestamp: January 11, 2017, 09:13:40 am
content: Just how much voltage were you putting in to get it to 150MHz, useful, but carrying around a power amplifier for that might limit the usefulness of it at the high end.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 11, 2017, 06:36:36 pm
content: Quote from: SeanB on January 11, 2017, 09:13:40 amI really had no idea. I was not trying to nuke the meter and the load was cold throughout the testing. The amplifier was idling. But, because you asked and it may actually be of interest to others, I ran the CEM at 154MHz, then adjusted the amplitude just to where it could read it. I used an active probe to take this measurement, so the numbers on the LeCroy are not scaled as they would be with the monitor port on my load. So roughly 3.2V.I can drive it direct with the signal generator in overload. Now if using a meter is this way is useful to someone, I can't answer that. Personally, I would use a counter.

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 11, 2017, 09:34:59 pm
content: That's good. For accurate frequency check I too prefer a frequency counter, but in my actual needs, I use this to check the average throughput of my embedded appliance and see if I can optimize it or not. That frequency is TTL 3.3 V so it's level is high enough, and hardly go beyond 40MHz: the clock is 85MHz and the maximum managed bit flip I can do in code will be near half of the MCU clock.

author: 3nigm4
author_rank: Regular Contributor
timestamp: January 11, 2017, 09:41:14 pm
content: Quote from: joeqsmith on January 10, 2017, 11:24:00 pmI tested only the voltage and the low battery appear at about 7V... at 4.7V the display starts dimming and at 4.5V is no more readable... the value read is stable even while dimming out

author: joeqsmith
author_rank: Super Contributor
timestamp: January 12, 2017, 12:07:39 am
content: With the new Extech, the battery indicator never comes on. It could be another problem with this particular meter. Even at 5.2 volts the display looks very good. In the first video where I show decoding the RF link, the battery was so low by the time I was done the display would really dim when it would transmit but it kept on running.I repeated the test at 40MHz. It's a little more sensitive. Roughly 6.6Vp-p is needed.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 12, 2017, 12:49:52 am
content: Someone was asking about the peak detect of the Fluke and I forgot I had ran this on the Extech.

author: joeqsmith
author_rank: Super Contributor
timestamp: January 23, 2017, 05:57:01 pm
content: Looks like there is a bug in the data logging.

author: morato
author_rank: Newbie
timestamp: March 19, 2020, 01:46:27 pm
content: Hi,Same equipments in worldCEM DT-9939/DT-9929 (original manufacturer)EXtech EX540/EX530 (Americas/Europe)Digitech/Jaycar QM1575 (Australia)Hikari HM2920/2900 (Brazil)Some information for calibration and repairVR1 - voltage reference -200mV (bottom left pot in shield)VR3 - AC+DC opamp offsetVR4 - Temp offsetVR5 - adjust for 10x gain used in temperature measurement (top right pot in shield)VR6 - milivolt adjustVR7 - true rms zero offsetVR8 - true rms converterVR10 - DC component for AC+DC true rmsIC3 - Voltage offset for temp measurementIC8 - frequency signal amplifier. Defective circuit here result in poor frequency detection and double frequency valueIC17 - Buttons encoderIC18 - Switch encoderThe fuse lock bits in microprocessor are not set and is possible to read the original firmware (USBasp).After download the original firmware I'm trying to make a new. The original is poor implamentation for capabilities of frontend and usability.Any posibilities:- Auto hold (touch hold)- Auto-range in relative mode- Min/Max/AVG with auto-range- 10 or 5 reads per second- Best bargraph sample time- Use 10x feature to low burn voltage in uA (removing R57).- Short beep for good diode- Flash backligth for continuity test- Fast response in continuity test- Extended setup options- Best average calc routine- Smooth mode for AC Volts- Compensation for true-rms converter error in 400 mV RMS operation. AD636 is disigned to 200 mV full scale and error grow significantly above 300 mV- Press any button for weekupI'm working with Hikari HM-2900 (without RF option = DT-9929) and I not have intention to implement communication with PC.The meter hardware is capable to implement good and useful features, but the worst software implementation result in poor usability.In the next few days I will publish the beta version of the new firmware (without RF communication).

author: joeqsmith
author_rank: Super Contributor
timestamp: May 06, 2020, 02:31:00 am
content: I went to use my EX540 today and it looks like it was borrowed. I mentioned how one time a the person who borrowed it, turned the knob past the dead stop which broke the plastic hex. Here's what I found today.

author: tautech
author_rank: Super Contributor
timestamp: May 06, 2020, 02:47:48 am
content: Quote from: joeqsmith on May 06, 2020, 02:31:00 amHmmm, I'll add DMM's to my list ofnever to be lentwhich is now: DMM, chainsaw and wife !Otherwise they all have the risk of being given back shagged !

author: MacGyver0606
author_rank: Newbie
timestamp: July 08, 2021, 08:30:24 pm
content: Hi, I'm looking for the calibration/adjustment procedure for any of these Multimeters, which are pretty much the same. I couldn't find it anywhere. Any help??CEM DT-9939/DT-9929 (original manufacturer)EXtech EX540/EX530 (Americas/Europe)Digitech/Jaycar QM1575 (Australia)Hikari HM2920/2900 (Brazil)

author: Bobson
author_rank: Regular Contributor
timestamp: July 17, 2021, 07:36:37 pm
content: My CEM DT-9979 has strange problem: sine wave voltage readings are approx 10% low (proper voltage seen using oscilloscope, APPA 506 and Fluke 8846A) at 2KHz-70KHz range, it becomes closer to actual at 70-100KHz. Triangle and pulse are much more exact. Also, CF (Crest Factor) readings are very random: it shows them sometimes, but rarely. There is calibration menu, but absolutely no docs. Some calibration features are rather straightforward, but I found nothing dealing with this problem.Will try to do the same test with DT-9989, which is much newer, but has very similar DMM part (AFAIK).

author: morato
author_rank: Newbie
timestamp: February 21, 2022, 07:18:22 pm
content: two years later... I am backNew firmware in beta versionAny posibilities:- Auto hold (touch hold) -OK- Auto-range in relative mode -OK- Min/Max/AVG with auto-range -OK- 10 or 5 reads per second -OK- Best bargraph sample time -OK- Use 10x feature to low burn voltage in uA (removing R57). -OK- Short beep for good diode -OK- Flash backligth for continuity test -OK- Fast response in continuity test -Yeah! Better- Extended setup options -OK- Best average calc routine -OK- Smooth mode for AC Volts -OK- Compensation for true-rms converter error in 400 mV RMS operation. AD636 is disigned to 200 mV full scale and error grow significantly above 300 mV -No!- Press any button for weekup -OKhttps://youtu.be/Z0y45DUREvE

author: morato
author_rank: Newbie
timestamp: February 21, 2022, 07:55:39 pm
content: Quote from: MacGyver0606 on July 08, 2021, 08:30:24 pmI don't have one.But... Don't touch in VR3, VR5 and VR10For DCSelect VDC, input precise 3V and adjust VR1 to correct readSelect mV range, input precise 300mV and adjust VR6For ACSelect VAC, short input and adjust VR7 to zero readingInput precise 3V AC and adjust VR8 to correct readIt's basic calibration procedure.