Are any of the Asian made Flukes AC-coupled? - Page 1
Forum section: electronics / testgear

author: Valver
author_rank: Contributor
timestamp: February 12, 2019, 01:30:11 pm
content: I work on tube amps and need to measure power supply and negative bias ripple voltage. USA made Flukes such as the 117 and 83V are AC-coupled on the AC voltage range, but I find no mention of this in the manuals for the Asian models. Thanks for any insight.

author: HKJ
author_rank: Super Contributor
timestamp: February 12, 2019, 04:17:33 pm
content: The Fluke 17B is AC coupled on AC.I include that information in all my multimeter reviews and a meter like Brymen use AC coupling, at least on some models.

author: Valver
author_rank: Contributor
timestamp: February 12, 2019, 08:51:21 pm
content: Great, thank you kindly. I bought 3 different multimeters this year, including the EEvblog BM 235, to replace my aging test equipment and wasn't expecting that none of these could measure any type of small AC signal whenever there's a DC bias higher than 20 volts. Not complaining, quite happy with the meters, but I'm forced to buy another one and at this point I'm not taking any chances.I'll hunt out your reviews, thanks

author: bc888
author_rank: Regular Contributor
timestamp: February 13, 2019, 01:56:51 am
content: Great stuff!https://lygte-info.dk/info/DMMReviews.html

author: Yansi
author_rank: Super Contributor
timestamp: February 13, 2019, 02:04:58 am
content: You can always use an external AC coupling capacitor.

author: 001
author_rank: Super Contributor
timestamp: February 13, 2019, 06:41:43 am
content: Quote from: Valver on February 12, 2019, 08:51:21 pmYeait is hard to see fluctuations smallest than range resolution

author: Valver
author_rank: Contributor
timestamp: February 13, 2019, 08:21:14 pm
content: Ah, good, Thanks, for the link.

author: Fungus
author_rank: Super Contributor
timestamp: February 13, 2019, 08:51:19 pm
content: Hioki DT4282 will simultaneously display AC voltage and either the frequency or the DC offset value.Quote from: Valver on February 12, 2019, 08:51:21 pmIt has no limit on the DC bias voltage (other than the 1000V DC CAT rating).The manual says the accuracy is less when you go under 1kHz and over 200V DC.Edit: Manual ishere

author: Valver
author_rank: Contributor
timestamp: February 13, 2019, 09:06:08 pm
content: Quote from: Fungus on February 13, 2019, 08:51:19 pmThere's the question of resolution with a dual display meter. The meter will be on the 1000v range due to the high DC voltage. I need to measure down to a few millivolts of AC ripple current. I am afraid that the resolution for the AC component will be poor.

author: Fungus
author_rank: Super Contributor
timestamp: February 13, 2019, 09:30:26 pm
content: Quote from: Valver on February 13, 2019, 09:06:08 pmThat's why I linked the manual, so you can read the specs.Edit: In the manual itlookslike it can measure the AC component on a 60mV range, which gives quite a bit of resolution on a 60,000 count meter. I'd make sure of that before parting with Hioki amounts of money though.

author: Valver
author_rank: Contributor
timestamp: February 14, 2019, 12:39:44 am
content: Nice meter, love to have one, but it's somewhat out of range for me. In truth a simple AC-coupled old school Voltmeter will do the job, but it's not easy to find out which models are and which aren't.

author: Valver
author_rank: Contributor
timestamp: February 14, 2019, 12:21:44 pm
content: Quote from: Yansi on February 13, 2019, 02:04:58 amBelieve me I've considered it, still considering it actually. Maybe modify a probe with a bypass switch... But no, not an option; I do a high volume of amp repair and it's such a nuisance. I can just get a Fluke 115 and end my misery, but I'm trying to find out what other choices I have.

author: Fungus
author_rank: Super Contributor
timestamp: February 14, 2019, 01:39:31 pm
content: Brymen BM869s might do it, but the specs are indecipherable (to me).I'm sure #joeqsmith could tell us.

author: Valver
author_rank: Contributor
timestamp: February 14, 2019, 05:10:49 pm
content: Quote from: Fungus on February 14, 2019, 01:39:31 pmThe major issue I have with Brymen is that it's so hard to see the decimal point, especially if the display is rapidly updating. When I'm working I tend to keep an eye on what I'm doing and glance to the side to check the meter. Now with my current Brymen BM235 I have to shift more attention away from what I'm doing. I'd look for better visibility or a different type of display if I were to buy an expensive meter. I do like the display of the UNI-T UT181A, (not that I would buy this meter).Actually, I have no need for a top-of-the-line model, I just need to measure AC and DC voltage independently. Must be AC-coupled. I have other meters for all other purposes.Hey, thaks you guys!

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 14, 2019, 05:19:28 pm
content: Just thinking..................Those meters are RMS-reading on their AC functions correct?But when measuring ripple, isn't it better to measure peak-to-peak values?And because of the non-sinousoildal ripple waveform, there isn't a straightforward way to convert from true RMS to pk-pk.With those considerations in mind, wouldn't it be easier to use a digital scope? And with the automated readings function, it will instantly give pk-pk readings. Or average, RMS or anything in between.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 15, 2019, 12:34:21 am
content: Quote from: Fungus on February 14, 2019, 01:39:31 pmIt depends. Switch it to the mV range, the one clamp should kick in. The PTC for that clamp is going to draw some current as it heats up. The signal they are trying to use may not like that load and the meter is certainly not going to like that HV.In AC or DCV, the clamps wouldn't come into play(assuming your not a kid playing with a MOT or exceeding the clamping voltage)but the meter may not be able to detect what they are trying to read. If they are looking for volts on top of a few hundred volts, it may be fine.So, for example.1) HV supply in series with injection transformer. Supply set to -400VDC. Injecting a 500mV 1KHz sine wave.2) Left BM869s looking at the output of the injection transformer showing frequency and ACV. Right BM869s reading in DC mode, looking at the DC and AC components. You only have 100mv res in the secondary display.3) Place Fluke 189 in series with a DC blocking cap. Monitor the voltage across the right BM869s.4) The Right BM869s is placed in the ACV mode while the Fluke 189 is placed into the mVAC mode. Note the voltage is too low for the BM869s to read it correctly. Also keep in mind that the power supply I am using of course has noise which is mixing with the noise I am injecting.5) You can see both the Brymen and AC coupled Fluke track.I played with a lot of tube equipment when I was a kid and just used an analog meter. I don't remember if my old Radio Shack meter had a DC block like that cheap analog meter I chopped up or not. That analog meter did have a separate connector with the cap which I think I integrated with the AC mode.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 15, 2019, 12:15:12 pm
content: 6) The HV power supply is set to 40 volts and applied to the BM869s on the left through the BM869s on the right. Left meter is set to AC/DC volts. Meter on the right is set to DCmA. Note that in this case, there is hardly any input current as expected.7) The meter on the left is now set to mVAC. Note that the current is now 10mA. This is due to the clamp.The transistor clamp is going to be around 7V. The resistor is 1K and the PTC around 1.5K. So 41V - 7V / 1K + 1.5K or around 14mA ish. The PTC is most likely starting to limit.

author: Valver
author_rank: Contributor
timestamp: February 16, 2019, 11:57:28 am
content: Great, detailed info! This answers many questions I had concerning the BM869. Can't thank you enough for taking the time!

author: joeqsmith
author_rank: Super Contributor
timestamp: February 16, 2019, 04:23:07 pm
content: Quote from: Valver on February 16, 2019, 11:57:28 amGlad you found it helpful. If there is something else you would like to know about the BM869s, feel free to ask.

author: Kean
author_rank: Unknown
timestamp: February 17, 2019, 11:48:26 pm
content: Quote from: joeqsmith on February 16, 2019, 04:23:07 pmJoe, I just want to say that it is much appreciated that you go to that effort to verify and then explain how it works. Cheers!

author: joeqsmith
author_rank: Super Contributor
timestamp: February 18, 2019, 12:55:59 am
content: Maybe Brymen will give me a raise. ..... Let's see, that 10% of $0. I'm rolling in it.Really though, glad to help. I bought all these meters to help answer questions, so don't be afraid to ask if there is a test you want to see.

author: Valver
author_rank: Contributor
timestamp: April 02, 2019, 06:35:06 pm
content: Here is a followup post to my quest for a modestly priced ac-coupled meter. While HJK's did answer my question exactly, I decided to pass on the 17B because it is an averaging meter and not true RMS:Quote from: HKJ on February 12, 2019, 04:17:33 pmSo, the only other alternative seems to be the Brymen. I didn't find any Brymen reviews that mention ac-coupling. Searching through Brymen specifications and manuals has proved fruitless. So has any Google search for Brymen. The Brymen site has no search engine. So I figured I'd email Brymen directly. Here is the message and their response: (names have been blanked out)_______________________________________________________________________Good Day,Do you manufacture any multimeters that are AC-coupled in the AC voltageand AC mV ranges?Thank You,********____________________________________________Hi *******,We have the multimeters that are AC-coupled only in the AC voltage ranges. For ACmV ranges, they are not AC-coupled.Best Regards,*********Product Marketing Manager/BrymenTEL: +886 2 2226 3396 ext. 12FAX: +886 2 2225 0025___________________________________________(Sigh) Maybe I should try a Ouija board ? Tarot?

author: rsjsouza
author_rank: Super Contributor
timestamp: April 04, 2019, 12:31:06 pm
content: I did some tests earlier this morning and was able to see that both my U1273A and U1282A meters are AC coupled on mV ranges. Later I will post some photographs (it is hard to resize stuff from the cellphone)I also tested my UT61E, UT139C and my Brymen BM857, but in all of them the protection kicks in.

author: Valver
author_rank: Contributor
timestamp: April 04, 2019, 02:53:42 pm
content: Quote from: rsjsouza on April 04, 2019, 12:31:06 pmDon't have to bother, Keysight meters are ac-coupled. from U1280 Data Sheet page 9:"AC and AC µA / mA / A specifications are AC coupled"But why have to buy a $662.00 (+15 % tax amazon.ca sold by keysight) meter to have this? It's more cost effective to go with an Asian product ... if I can find one, lol.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 04, 2019, 03:27:50 pm
content: Perhaps try to bid on one?eBay auction: #192874206504I post the photographs below anyways, as the cheaper alternative (BM857) has enough resolution to measure for 10s or 100s of mV on the AC range. I don't have a 400VDChandy (it is stored somewhere), but with 42VDCit shows:100mVPP1kHz sinewave on top of ~42VDC.mVACon U1282A - no external capmVDCon U1282A - no external cap. Input isnot decoupledmVACon U1282A and BM857 - external 1nF capmVACon U1282A and BM857 - no external cap. Input of BM857 isnot decoupledmVACon U1282A and VAC+DCon BM857 - no external cap. Resolution on BM857 is not enoughmVACon U1282A and VACon BM857 - no external cap. Resolution on BM857 is enough to capture those mVACmVACon U1273A and VACon BM857 - no external cap. U1273A is decoupled and resolution on BM857 is enough to capture those mVAC(the UT61E was useless above 5VDCof offset)

author: rsjsouza
author_rank: Super Contributor
timestamp: April 05, 2019, 07:36:09 pm
content: My Fluke 27/FM is also AC coupled. You can get one usedverycheap.eBay auction: #293027184096Or another not so cheap:eBay auction: #382879102481

author: Valver
author_rank: Contributor
timestamp: April 05, 2019, 07:55:42 pm
content: Great post with the meter comparisons, quite informative, thanks. It illustrates well why I'm looking for an AC-coupled meter.I'm surprised that it's become so difficult to find, all of my prior meters were AC-coupled and I assumed that newer meters would be as well.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 05, 2019, 08:46:14 pm
content: I suspect it may be due to the fact this particular specification is not emphasized on the A-brand meters' specification sheets, thus it is not copied by the off-brands.Another explanation may be that, nowadays, the vast majority of meters in the marketplace come from off-brands - in the past one would simply be resigned to the idea of having to save a mountain of money to buy a Simpson, Avo, Fluke, Hioki, Sanwa...

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2019, 05:21:39 am
content: Quote from: rsjsouza on April 05, 2019, 07:36:09 pmDamn, those things are going cheap now! (if you live in the USA and don't have to pay $150 shipping)

author: rsjsouza
author_rank: Super Contributor
timestamp: April 06, 2019, 12:25:36 pm
content: Quote from: Fungus on April 06, 2019, 05:21:39 amYes, the US is the test gear mecca. Interestingly enough, I bought mine several years ago when someone probably got a massive batch and were selling them foreven cheaper. Mine came in really great condition, but someone took the effort to remove the sticker in the back with the serial number and all other details about the unit... (??!??)

author: joeqsmith
author_rank: Super Contributor
timestamp: April 06, 2019, 01:07:09 pm
content: A similar test using the Yokogawa TY720.https://youtu.be/4aCN-uLeO5s?t=3162

author: Valver
author_rank: Contributor
timestamp: April 06, 2019, 03:09:12 pm
content: Quote from: joeqsmith on April 06, 2019, 01:07:09 pmYes! Yes! The first test that I see that represents my actual situation. I routinely need to measure small signal ripple and noise on 500V power supplies and -50V negative power supplies found in tube audio gear.A clear example of the advantage of an AC-coupled meter for this application.Interesting meter the TY720, seems to be AC-coupled when on AC ranges (User Manual p.71) yet still capable of AC+DC

author: HKJ
author_rank: Super Contributor
timestamp: April 06, 2019, 03:16:37 pm
content: Quote from: Valver on April 06, 2019, 03:09:12 pmThe AC+DC is usual done in the DC position.

author: Valver
author_rank: Contributor
timestamp: April 06, 2019, 03:38:58 pm
content: Quote from: HKJ on April 06, 2019, 03:16:37 pmYes, obviously, but not all meters that will provide AC+DC functionality will also specify AC-coupling on the AC ranges.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 06, 2019, 04:00:27 pm
content: Any idea how low of voltage you actually need to measure and what frequency range? I would have thought a scope would work better for what you were describing but I'm still a bit confused about what you are up to.

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2019, 04:14:09 pm
content: Quote from: rsjsouza on April 06, 2019, 12:25:36 pmMe too.I think that was when the US Army was switching to a new model or something so they were dumping them from their stores. Mine was untouched old stock, apart from a US army calibration sticker (which it still wears proudly). I think I paid about $75 with shipping. International shipping from the USA has gone up massively since then, and the eBay "Global Shipping" has made things even worse, not only is it more expensive but they garantee you pay taxes (and I'm sure they skim money off the tax, they don't give you any VAT paperwork and I'm sure they aren't paying full rate in Ireland).

author: rsjsouza
author_rank: Super Contributor
timestamp: April 06, 2019, 05:21:41 pm
content: Quote from: Fungus on April 06, 2019, 04:14:09 pmWow... NOS... You are really lucky! Congratulations!When I used to deal with freight forwarders and carriers on a regular basis, they were always taking money on top of taxes - in Brasil we begrudingly paid this but were a bit more understanding due to the horrendous bureaucracy involved (the customs agents took their share as well). Nowadays with internet and automation... Yeah, they are thieves.

author: Valver
author_rank: Contributor
timestamp: April 06, 2019, 05:41:10 pm
content: Quote from: joeqsmith on April 06, 2019, 04:00:27 pmI work with musical instrument amplifiers, servicing, modification and restoration of vintage tube equipment. I use an AC-coupled meter to get a quick idea of the condition of the filter caps in power supplies.Basically I measure power supplies range from 250VDC upwards into the 700VDC range. While lower voltage negative bias supplies are below -100VDC. The over-riding AC ripple component is anywhere from 15mVAC to 6VAC depending on what stage of the power supply I am measuring. Frequency is all line related 120HZWith old bad caps the amount of ripple will be several times greater than a known acceptable amount. I then proceed to re-cap the amp or make an estimate of the repair. I am not concerned with an accurate picture of the ripple and noise, if I were I would certainly use a scope, but rather with a quick analysis as to whether parts need replacement or whether I should look for a problem elsewhere. I will use a scope to look at the audio while doing this, but power supply and bias voltages are more quickly measured with meters, otherwise I'll be forever tweaking range and position controls.AC-coupled meters work perfectly well for what I do, but not at the price of a new scope. So i'm hoping there is a more modestly priced Asian alternative. Meanwhile, I'm making a series capacitor box.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 06, 2019, 10:34:04 pm
content: Quote from: Valver on April 06, 2019, 05:41:10 pmSo nothing really radical. The higher class DC coupled meters would be fine if using their voltage function but their cost is really the issue?

author: Valver
author_rank: Contributor
timestamp: April 07, 2019, 07:16:33 pm
content: Quote from: joeqsmith on April 06, 2019, 10:34:04 pmI need an AC-Coupled meter (ACV and ACmV ranges). 1000V DC, 750V AC, w bar graph. A higher class DC coupled meter with adequate resolution would be nice but I don't really think that I'll find a moderately priced one.Cost is the issue because I don't need any advanced features and I will need to buy at least 2 of these because I have 2 work benches.Presently I am using a Radio Shack Smart2 bench meter that I bought in 1995 for under $100.00. it does everything that I need for this application but I want to replace it with a more recent model. I also had an even cheaper Micronta meter that worked well. All the DMMs that i have ever used have been able to measure ripple voltage, because I can only assume that AC-coupling was the norm then.Here is a typical case:1: The Patient (DUT)2: DC measurement of First Stage of DUT Power supply = 440VDC3: AC measurement of First Stage of DUT Power supply =~ 4.5VAC on meter, 4.6V on scope. This is 'normal' for this amp4: I've had a request for a photo of my new Aneng V8 so here it is connected with a series de-coupling cap5: DC measurement of Second Stage of DUT Power supply = 431VDC6: AC measurement of First Stage of DUT Power supply =~ 285mVAC on meter, scope can't trigger properly because I need to use 100x probes when measuring high voltage. scope is only seeing 28uV. Notice that the Smart2 will autorange down to the 400mV scale, no need to switch to a separate mV range!!7: AC measurement of Third Stage of DUT Power supply =~ 20mVAC on meter, insufficient voltage for scope, 200uV using 100x probeThanks again for all you valuable help

author: rsjsouza
author_rank: Super Contributor
timestamp: April 07, 2019, 08:24:50 pm
content: Nice photographs!I agree with Joe: it is a typical scenario that older equipment (VOMs, VTVMs) were much more concerned. Nowadays, where multimeters actually warn you that 30V is a high voltageby showing a lightning sign on the display, their designs are much more concerned with other features.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 07, 2019, 10:11:35 pm
content: Now that we know it's a problem with price, you brought up $100 in 95. That's $165 in today's dollars. Is this your budget for a single meter?Looking at that old Tachikawa analog meter I have, it was DC coupled. The cheap analog one I bought had a separate jack that would allow AC coupling. Looking at the manual for the Simpson 260 series 6, it also has a separate jack. Same for the 260 5.

author: Valver
author_rank: Contributor
timestamp: April 08, 2019, 01:27:54 am
content: Quote from: joeqsmith on April 07, 2019, 10:11:35 pmWell, I'll go for that. Depends on the port of entry though. Asian, no problem, never paid any tax, shipping, or handling on Asian items. Items from the US usually cost much more. A set of $17.90(US) Probe master Leads shipped by USPS will cost $64.07(CA) once shipping, taxes and handling fees are added.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 08, 2019, 02:06:30 am
content: Now that we have an idea on price, there may be some cheap meters that will do what you want. Did you not like the Fluke 17B? I have the 17B+ and that thing is really solid. IMO, the one shortcoming that meter has it that it's averaging. Do you need TRMS? Narrowing the choices....

author: Valver
author_rank: Contributor
timestamp: April 09, 2019, 02:06:48 pm
content: Quote from: joeqsmith on April 08, 2019, 02:06:30 amThe 17B+ is the top contender, and at the moment the only contender, so far. Large, readable display ... very nice. It was the reason for this post because I couldn't find any mention of coupling in the specs or in the user manual. HKJ promptly informed me that it was AC-coupled and that some Brymens were as well.The first issue that I have is whether the 17B+ is ac-coupled in the millivolt range, other Fluke models like the 117 are not. Quote from the 117 manual:"AC volts is ac-coupled. Auto-V, LoZ and ac mV are dc-coupled "Of course the second issue is the fact that it's averaging. Working with guitar amps and overdrive circuits i deal with quite a bit with non-sinusidal waveforms. I wouldn't be able to use this meter in conjunction with my other ones. The discrepancy would drive me crazy.I am still wondering which Brymen meters are AC-Coupled. Anyone have a clue?Cheers

author: rsjsouza
author_rank: Super Contributor
timestamp: April 09, 2019, 02:50:56 pm
content: Quote from: Valver on April 09, 2019, 02:06:48 pmI couldn't find a Brymen meter that has mVACcoupled, but the BM857 I mentioned before has enough resolution for your range of measurements in VAC, is decoupled and falls into your budget.https://www.tme.com/us/en-us/katalog/?search=bm857That wouldn't have the feature you are looking for, but it will certainly solve your problem. And you will have an excellent meter in your hands!

author: HKJ
author_rank: Super Contributor
timestamp: April 09, 2019, 03:32:53 pm
content: The first issue that I have is whether the 17B+ is ac-coupled in the millivolt range, other Fluke models like the 117 are not.It is not, when you have a shared mV DC/AC range it will not be AC coupled. AC coupling needs a separate position on the range switch, electronic switching can only handle a few volts.My review do also specify that.

author: Valver
author_rank: Contributor
timestamp: April 11, 2019, 12:13:23 am
content: Quote from: HKJ on April 09, 2019, 03:32:53 pmIt is not, when you have a shared mV DC/AC range it will not be AC coupled. AC coupling needs a separate position on the range switch, electronic switching can only handle a few volts.Thanks for clearing that up. I should have asked that question from the start.

author: Valver
author_rank: Contributor
timestamp: April 11, 2019, 12:37:50 am
content: Quote from: rsjsouza on April 09, 2019, 02:50:56 pmReally? That's great, didn't realize that the BM857 was in that price range. It looked expensive and scared me off, lol.

author: joeqsmith
author_rank: Super Contributor
timestamp: April 11, 2019, 01:01:14 am
content: I have no idea what that stage three DC bias is but keep in mind that the meter is only 50,000 counts. Even your stage 2, what you have now would work better if you really need to get down this low.I did look through the few meters I have and none would do what you are asking for. Hopefully you will find something better suited without the need for an external capacitor.

author: rsjsouza
author_rank: Super Contributor
timestamp: April 11, 2019, 01:31:19 am
content: Quote from: joeqsmith on April 11, 2019, 01:01:14 amI had the impression the OP mentioned a minimum of 15mVACon top of the DC bias. If so, the 5VACrange with 50000 counts has enough resolution to see this signal.

author: Valver
author_rank: Contributor
timestamp: April 11, 2019, 02:20:27 am
content: Isn't the minimum resolution limited due to the True RMS converters ?From Fluke 179 spec sheet with regard to the 600mV range:"Unspecified input levels on the lowest ranges are:•AC voltage: below 5% of 600 mV AC, or 30 mV AC"From Fluke 80's series V manual:"AC conversions for Model 87 are ac coupled, true rms responding, and valid from 3 % to 100 % of range, except 400 mA range (5 %to 100 % of range) and 10 A range (15 % to 100 % or range)"i would imagine that the Brymen has similar restrictions. 3% of 5V is 150mV (+40 digits and .8% accuracy if I read the specs correctly).rsjsouza, I did notice that your readings were quite similar between meters. Perhaps because you were using a sine wave?