Design Error in ANENG AN8008 and 8002 - Page 1
Forum section: electronics / testgear

author: mullecy
author_rank: Contributor
timestamp: September 01, 2017, 08:55:13 pm
content: Hi! I have a little story for u!Those meters are quite popular because of low price for good VDC accuracy (effective VDC error 0.1%<0.5% specified) for a low price (at the cost of CAT protection but at that price what do you expect...)But it seems that I discovered a flaw in the design.I was measuring voltages and had a 8008 connected in parallel with my usual meter.Then it switched off after some time and I put it in "OFF" position.Later I disconnected the ANENG.My usual meter was in "delta" mode so when I looked at it I immediately noticed that the value changed (a few last digits) after disconnection.So I plugged it again (but still in OFF) and bingo the delta value was back to 0.0000I investigated and used another meter in ohm mode to measure the 8008 impedance: only 1.2MOhms in OFF position between COM and V terminals!I have more than one ANENG and all have the same issue: 1.2MOhms impedance in OFF position (1.3 for 8002) !!!!!!

author: mullecy
author_rank: Contributor
timestamp: September 01, 2017, 09:28:04 pm
content: Proof...

author: Mark Hennessy
author_rank: Frequent Contributor
timestamp: September 01, 2017, 09:31:52 pm
content: Yes, this has been mentioned elsewhere. The AN860B+ does the same, and no-doubt there are others.It seems that the PTC and high-speed clamp transistors are switched in when in the off position. Normally, this circuit supplies the current for resistance, continuity, etc.An interesting test is to connect the meter to a bench power supply. Wind up the voltage to about 20V, and you'll see about 10mA flow. But watch that value slowly fall as the PTC warms up...Think of it as being like a low-Z mode, just like Dave's BM235. Only undocumentedAs to why they did this, I've plenty of speculation, but no real idea. The fact they've done it to at least 3 meters suggests it's intentional, for whatever reason.

author: mullecy
author_rank: Contributor
timestamp: September 01, 2017, 10:18:43 pm
content: Thx for your reply.I have searched before posting but didn't find anything on it... But I'm not an ANENG specialist.I bet it's a error and they kept copying the design from one meter to the next one without thinking...I did your test:The 20V test is a bit too gentle because it's more or less stable arround 10mA.So I tried at 30V: the current starts near 20mA and then goes down to arround 10ma.So it's far worse than what my meter says... (because it probes at low voltage)R=U/I=2kOmhs at 20V and 1.5 to 3kOmhs at 30V(Of course it's not really a resistor... so this is just "equivalent" value)So at voltages found on the bench it's in the KiloOhms range !!!!!! That's crazy!Has anyone pluged an ANENG meter in 220V in OFF position ?The PTC is going to become very hot...Here's a table of a meter increasing voltage progressively. Under 16V there's no "PTC heating" effect. But above, I have to wait for the current to stabilize (or boost the voltage a bit for a few seconds to speed up heating)Code:VmARW10.0025000000.00000220.08250000.0001630.18166670.0005440.29137930.0011650.5198040.002556160000.00671.5944030.0111382.2236040.0177692.8631470.02574103.5228410.0352114.1926250.04609124.8824590.05856135.5523420.07215146.2222510.08708156.8721830.10305167.4521480.1192178.0321170.13651188.5920950.1546219921110.1712010.219610.2042110.220590.21422510.224510.255309.431910.282Note that the equivalent resistance drops very fast to around 2KOhms with voltage...Those are not instantaneous values: I let the PTC warm up. If there's a sudden increase in voltage, the current is much higher for a short time.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 02, 2017, 02:33:48 am
content: I mentioned it in the couple of videos I made and posted about it here as well. Yes, I have ran them on 220V in the off position. Yes, the PTC gets hot. Pretty much the nature of it. No, I was not able to damage the mechanical selector switch or clamp by doing this.Its a cheap meter. Don't expect too much from it.https://youtu.be/TSGLA9heboY?t=1306

author: mullecy
author_rank: Contributor
timestamp: September 02, 2017, 10:22:57 am
content: Great video! Quite exhaustive!My question was more: how many cycles will this cheap PTC handles (knowing that even at 20V you start to heat it up in off position) ?

author: joeqsmith
author_rank: Super Contributor
timestamp: September 02, 2017, 02:04:45 pm
content: I assume you are asking how many AC cycles at 220V. I would guess the failure rate for a PTC is not published in cycles but rather hours of operation. Some of the ones I had bought when looking at the UT61E could handle 1000V without any series resistance. Looking at the datasheet for that part, they do not publish MTBF numbers on the datasheets. Looking at the parts from TDK, they do have a fair amount of reliability data. The part used in this meter is marked 03M made by APR.APR datasheetThey have a switch life but I am not sure what that means. These do not appear to be certified like the parts found in higher quality meters.Another video I made for the 860B showing the same problem. Again, it's not a high end meter so don't expect too much out of it.https://youtu.be/4PjmFqzlfLc?t=1382

author: stj
author_rank: Super Contributor
timestamp: September 02, 2017, 08:29:55 pm
content: why the hell would anybody connect the meter in the "off" position?that creates an extra risk when you have to switch it on - while connected.only a dumb sh1t would do such a thing!this isnt a kitchen appliance, it's assumed if you need something like this, then you know how to use it!

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 03, 2017, 04:19:00 am
content: Quote from: stj on September 02, 2017, 08:29:55 pmAre these conditions are mentioned in manual? Is there any huge warning about the device is behave not like other meters and something about avoiding connecting it to mains in "off" state?Do you really assumed that anybody who have a meter of this grade perform all around check for any "features" that may hidden in it's design?I don't think so.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 07:19:36 am
content: Quote from: WhichEnt2 on September 03, 2017, 04:19:00 amLine 10 of the AN8008 Manual says: "3) Disconnect the test leads from the circuit before changing the mode"How you convert this 'design error' into a hazard without breaking that rule is up to you.Quote from: WhichEnt2 on September 03, 2017, 04:19:00 amIf you have a meter of this grade and you store it with the test leads inserted in a mains socket then you deserve to have a couple of them fail on you. Maybe you'll learn not to do it.

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 03, 2017, 07:51:57 am
content: QuoteI'm not saying that. I call it feature.No, I don't have no meter of this grade. I have ut210e which performed on same chip and it have about 10 MOhm impedance in "off" position.So I don't really care on safety of these meters.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 08:01:54 am
content: Quote from: WhichEnt2 on September 03, 2017, 07:51:57 am

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 03, 2017, 08:10:27 am
content: Quote from: Fungus on September 03, 2017, 08:01:54 amI don't think current clamp meter can be directly compared to usual dmm.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 08:26:42 am
content: Quote from: WhichEnt2 on September 03, 2017, 08:10:27 amOK, so you don't have a meter of thistype."grade" would refer to quality. Neither of these meters is a Fluke.

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 03, 2017, 08:43:38 am
content: QuoteI am sure, and exactly meant the grade.Different type is obvious, and even if used outside of current clamp functions it don't have any issues specified in OP.Fluke is up there. We're discuss about much lower grades, a bit above the bottom, isn't it?

author: kalel
author_rank: Frequent Contributor
timestamp: September 03, 2017, 08:49:54 am
content: Quote from: Fungus on September 03, 2017, 08:26:42 amJust out of curiosity, is there another name that gives the same impression? It's always Fluke we hear about.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 09:42:48 am
content: Quote from: kalel on September 03, 2017, 08:49:54 amThere are other brands but Fluke is the measuring stick.

author: b_force
author_rank: Super Contributor
timestamp: September 03, 2017, 01:50:05 pm
content: Quote from: joeqsmith on September 02, 2017, 02:33:48 amExcellent tests!!!!Pretty much what you would expect from these little meters.Still don't see how these meters "WILL kill you".I have seen much worse from officially tested high professional equipment.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 02:24:44 pm
content: Quote from: b_force on September 03, 2017, 01:50:05 pmYou didn't see the meter jumping around in the box at that start of the video? Would you like to be holding it in your hand?Joe uses low energy levels, much lower than could come down the line in a CATIII/CATIV environment.

author: kalel
author_rank: Frequent Contributor
timestamp: September 03, 2017, 02:34:12 pm
content: Quote from: Fungus on September 03, 2017, 02:24:44 pmI wouldn't.Just out of curiosity, even in mains checking situations, is it standard to hold the meter in your hand? I usually find it easier for any (low voltage) checking to have the meter on a table, floor, or if nothing is available, to hang it on something if possible. Now I don't know the "usual way" that people use to work with dangerous voltages.

author: b_force
author_rank: Super Contributor
timestamp: September 03, 2017, 02:48:05 pm
content: Quote from: Fungus on September 03, 2017, 02:24:44 pmIt would be a scary experience maybe, but it doesn't KILL you.Not even close.Maybe you will end up with a blister.(which I get anyway from soldering, lol)If i already hold it in my hands, as mentioned above I seldom do that anyway.In fact in my whole career I have never seen anyone holding a meter in his hands while measuring something, because mostly you need your hands for something else.And ones again, I don't see how on earth somebody could use these meters in these CAT environments.Mostly because that means you are working in a professional environment anyway, which by default means you have to use properly tested and licensed equipment.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 03:54:49 pm
content: Quote from: kalel on September 03, 2017, 02:34:12 pmNo.Magnetic hangers aren't a convenience feature, they're a safety feature. You'd also be wearing big gloves.Quote from: b_force on September 03, 2017, 02:48:05 pmDoes only "death" count as a reason not to use one?As noted earlier, joe uses low energy levels. In real life the surge can last much longer than a couple of microseconds.Quote from: b_force on September 03, 2017, 02:48:05 pmYou might also be temporarily blinded by the flash and fall off a ladder, get permanent hearing damage from the bang, etc., etc.Not 'dead', but not things you'd want. Not worth saving $25 for.

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 03, 2017, 04:06:53 pm
content: Quote from: b_force on September 03, 2017, 01:50:05 pmEven if it provoke you to fall from a ladder?

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 04:14:05 pm
content: Quote from: WhichEnt2 on September 03, 2017, 04:06:53 pmOr even just jump backwards, fall over, bang your head.http://www.fluke.com/fluke/uses/comunidad/fluke-news-plus/articlecategories/safety/arc%20flashhttps://www.youtube.com/watch?time_continue=9&v=i9jpwGTy66g

author: b_force
author_rank: Super Contributor
timestamp: September 03, 2017, 04:28:20 pm
content: Quote from: Fungus on September 03, 2017, 03:54:49 pm(you're not serious right?, I hope......)Guess people need to read the whole post.Anyway, it's useless to keep discussing about it like this.I think it is overly dramatic (understatement).Yes there are some things you need to take into consideration, use your brain.But isn't that extremely obvious if you buy gear like this?Or in other words, if you're the type of person that is heavily concerned and very anxious about the tiniest little thing.Don't buy it.Or maybe just choice another hobby, before you know, you will burn into your artery in your wrist with your solder iron and bleed to deathAnyway, case closed for me.If you don't like the meter, don't buy it.

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 03, 2017, 04:31:35 pm
content: Quote from: Fungus on September 03, 2017, 04:14:05 pmNice combination.I have been injured by an arc flash a couple of times. And no you don't need no dmm for such experience.

author: Fungus
author_rank: Super Contributor
timestamp: September 03, 2017, 05:13:35 pm
content: Nobody with any education should be poking the probes of a $20 meter into a mains panel anyway so this is moot.Joes vidoes are just to find the limits of where bad thingsstartto happen.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 04, 2017, 06:26:07 pm
content: Quote from: Fungus on September 03, 2017, 05:13:35 pmThe videos have evolved somewhat into somewhat detailed reviews. People seem to get more out of me showing some of the strange problems I see rather than just running the transient tests on them. At least the feedback has been mostly positive.To your point, when it comes to the transient tests, for the most part, I agree. However there are cases where I think to the untrained eye the results could be very misleading. As you mention in my tests, the energy levels are very low. This is true. There is a reason those generators seen in Fluke's videos are physically so large and mine takes up a little space on my desk.If we look at the AN8008/2 for example, watching Dave's insulation tests you notice how there are two contacts that arc. These are the pads for the shared current input and it arcs because first its a shared input, the pad spacing and the TVS has a fairly low breakdown returning to common. Because I do not test the current inputs, I would not know if the TVS or fuse were damaged. It's also possible that the contacts break down and the TVS saves the meter from damage because the energy available is so low. It is possible that if the meter were ran to the IEC standards, it would be damaged at a lower voltage.I've said many times I am less concerned with the meters safety than I am it's ability to survive some basic electrical tests. My tests will most likely continue to reflect this. So don't look for any sort of case splitting transients in the future.Quote from: WhichEnt2 on September 03, 2017, 04:31:35 pmInteresting. Since I have started testing these meters, I have heard some first hand stories from various people about work related accidents. We were out to dinner with some friends last weekend and they were telling me about a group of workers that had been brought in to do some maintenance on some 4KV switch gear. I understand there were four workers. Area had been shutdown. Workers enter and one person opens one of the systems they were going to service and leaves. Worker two starts working on this system and comes in contact with the main. No equipment involved. This worker is pretty much gone, physically gone. Plasma moves it's way around the area and injures the two other workers. Hospital at first is not going to work one of the persons as they assume he will not survive. Burns were over much of his body.A friend of mine introduced me to another friend of his and he brought up the whole meter testing. Of course I get the Why? So I explain things in simple terms and it turns out this person was a retired master electrician. He starts telling a story of how he never saw a point in PPE until one day they were also working on some switch gear. He and one other guy were going to take some routine measurements. They suit up and enter the room. He is holding the meter, the second guy has the probes. The probes were several feet long. The probes get attached and the meter instantly blows up in his hands. No injuries but it changed his views on PPE. At this place, that required an investigation to determine the root cause. The meter had to be returned to the manufacture for failure analysis. I was told that in this case, the meter had a defect.I heard of one other person (sounded like a young electrician) who they said had hooked up a meter to a large AC bus and the meter again blew apart. They did not know what the root cause was.Because of my work, I don't get involved very often with high energy AC. I have visited some places (like that power plant I had mentioned) but it's not to do any sort of work. I was at a place a while back and their electrician asked me about measuring some 20KA circuits. I asked if I could see what they were trying to measure as I just could not wrap my head around it. Funny to see a connector rated for that sort of current. Water cooled. Any time I need to measure current in CAT III, I have the HIOKI and use the clamps. Personally for a handheld, I really have little need for the internal current and if I were working in CAT III, I would not want the feature.

author: PA4TIM
author_rank: Super Contributor
timestamp: September 04, 2017, 07:20:55 pm
content: Quote from: mullecy on September 01, 2017, 08:55:13 pmJust tested my 8002, it measures between 1.5M and 92k depending the meter I use to measure the resistance. Only Fluke I have here in the living is a 8020. If I use that as victim the resistance is also low in the off position. Not so strange because the meters I used, all generate different voltages and currents. (most are analog meters and some generate 20V)So nothing wrong with the Aneng. Besides that i never switch a meter off with testleads still connected. And I do not use the Aneng for serious stuff. It is here in the living to measure the voltage of rechargeable AA batteries. And sometimes check a fuse or f.i. a 6V lightbulb in my pinball machine. For serious work I use serious meters, not this cute toy meter

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 05, 2017, 01:50:34 pm
content: Quote from: joeqsmith on September 04, 2017, 06:26:07 pmThanks for the stories.Looks like blowed up dmm that change view of using PPE been connected to very high energy source.Check this:time 8:50 As far as I know he was not injured because he was wearing an arc flash protection suit.Look in the attach. The old soviet style stuff, never been upgraded since early '90s.3rd one pole circuit braker, I short input wire of it to metal case with a tip of insulated screwdriver.Notice how one of the phases of input cable is touching the screw on the busbar through insulation. This is the source of second arc flash.First arc is just burned out that wire on 3rd circuit braker and dissapears. Second is lasts for about a 2 to 3 seconds, evaporate aluminum busbars to my face.I was lucky enough not to catch a full exposition and get away as soon I'm realise that event is not routine short in switchbox which usually don't continue over a half of second or so.Exposed skin is tanned very dark and this tan is peeled off in a couple days.I was wearing thin synthetic gloves partially covered in latex. Three fingers on the left hand got burns in that place where fabric not covered by latex.And I think there is no need to describe symptoms of thishttps://en.wikipedia.org/wiki/Photokeratitisin full palette (not too much this time, because I apply a lot of artifical tears stuff in the same day).In the result I was off the work for a week or so.Other incidents with arc flash is just messing with a wire to hook up a battery charger and similar unclever stunt shit.As electritian I use (a employers) DMM or current clamp or insulation meter or other measuring stuff a couple of times in a year.For most test situations simple led indicator (attached) or fluke non-contact indicator is enough.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 06, 2017, 02:21:20 am
content: LOL! I am not sure what our feed is, maybe 200A. It's not marked. There is no way I would go near the input side with a screwdriver without pulling the meter. Guessing the transformer that feeds us could handle a fair amount.We had an electrician once climb up a ladder and put a screw driver across one of the main feeds for the building, as I understand it, intentionally!! I think that was a 440 feed. Fairly good size flash and He came crashing down. Lucky for him he was not hurt too bad. Maybe all the shame kept him alive after that. When he retired, they had the screwdriver made into a trophy for him.I would need to ask my friends what gear that was on.

author: WhichEnt2
author_rank: Regular Contributor
timestamp: September 06, 2017, 12:26:31 pm
content: I just entangled in and out side of circuit braker.Also similar type of that 3 pole circuit braker sometime doesn't have any magnetic trip, just thermal. I don't know what type are there, but disassemble a few similar and they don't have it.

author: Fungus
author_rank: Super Contributor
timestamp: September 06, 2017, 12:58:18 pm
content: Quote from: joeqsmith on September 06, 2017, 02:21:20 amGotta check if it's live or not before touching it.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 06, 2017, 05:41:27 pm
content: Quote from: Fungus on September 06, 2017, 12:58:18 pmThere are better ways to do that but I understand that some people have a thing for screwdrivers.

author: Fungus
author_rank: Super Contributor
timestamp: September 06, 2017, 06:11:45 pm
content: Quote from: joeqsmith on September 06, 2017, 05:41:27 pmIf the thing was supposed to be powered off then a screwdriver test might have saved his life.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 07, 2017, 12:56:37 am
content: Quote from: Fungus on September 06, 2017, 06:11:45 pmThat's a good point but an average intelligent person may have noticed with it being a work day and the factory running, that bus was still live. No idea what was going through his head.

author: bitseeker
author_rank: Super Contributor
timestamp: September 07, 2017, 02:21:49 am
content: Quote from: PA4TIM on September 04, 2017, 07:20:55 pmA few additional points of reference when in "off" mode.Keysight U1282A: OLKeysight U1252B: OLKeysight U1272A: 1.8K Ohms (same as in LoZ mode)Greenlee DM-820A: OL

author: crazyguy
author_rank: Regular Contributor
timestamp: September 07, 2017, 02:32:04 am
content: Quote from: bitseeker on September 07, 2017, 02:21:49 amHow about the input impedance in sleep mode ?Tektronix TX-3 : OFF Position : OL; normal mode : ~ 11M; Sleep Mode (~10 min) 11M; Sleep Mode (~15 min) OLPeakMeter PM18C: OFF Position : > 40M; normal Mode : 10-11M; Sleep Mode > 40 M

author: Fungus
author_rank: Super Contributor
timestamp: September 07, 2017, 09:42:23 am
content: Quote from: joeqsmith on September 07, 2017, 12:56:37 amHim: "Are yousurethis thing is off?"Billy Ray: "Turned it off myself, not a minute ago."Him: "Let's see now..."The available amperage might have been unexpected but screwdriverscanbe a life-saving piece of gear in the right hands.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 07, 2017, 09:54:49 am
content: Quote from: Fungus on September 07, 2017, 09:42:23 amOne person. Screwdriver did some damage and managed to loose power for a fair part of the plant. Not sure what the lost down time alone cost the company but it was not enough to remove him.

author: Fungus
author_rank: Super Contributor
timestamp: September 07, 2017, 10:31:17 am
content: Quote from: joeqsmith on September 07, 2017, 09:54:49 amYou know more details than me, obviously.When I was younger we used to charge up big capacitors and short them with things for fun. We could weld screwdrivers to the contacts and pick up the capacitor with the screwdriver, no problem.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 08, 2017, 01:33:30 am
content: Quote from: Fungus on September 07, 2017, 10:31:17 amThere are apparently people out there that believe that this is how I test the multi-meters (Direct discharges with capacitors). At some point, you have to give up on stupid people.