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My Fluke 27/FM is also AC coupled. You can get one used very cheap.
eBay auction: #293027184096
Or another not so cheap:
eBay auction: #382879102481 -
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.
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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...
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My Fluke 27/FM is also AC coupled. You can get one used very cheap.
Damn, those things are going cheap now! (if you live in the USA and don't have to pay $150 shipping)
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Yes, 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 for even 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... (??!??)My Fluke 27/FM is also AC coupled. You can get one used very cheap.
Damn, those things are going cheap now! (if you live in the USA and don't have to pay $150 shipping) -
A similar test using the Yokogawa TY720.
https://youtu.be/4aCN-uLeO5s?t=3162
Yes! 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
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Interesting meter the TY720, seems to be AC-coupled when on AC ranges (User Manual p.71) yet still capable of AC+DC
The AC+DC is usual done in the DC position. -
Interesting meter the TY720, seems to be AC-coupled when on AC ranges (User Manual p.71) yet still capable of AC+DC
The AC+DC is usual done in the DC position.
Yes, obviously, but not all meters that will provide AC+DC functionality will also specify AC-coupling on the AC ranges.
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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.
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I bought mine several years ago when someone probably got a massive batch and were selling them for even 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... (??!??)
Me 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).
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Wow... NOS... You are really lucky! Congratulations!I bought mine several years ago when someone probably got a massive batch and were selling them for even 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... (??!??)
Me 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).
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. -
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.
I 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 120HZ
With 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.
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I 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.
So nothing really radical. The higher class DC coupled meters would be fine if using their voltage function but their cost is really the issue?
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 120HZ
With 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. -
So nothing really radical. The higher class DC coupled meters would be fine if using their voltage function but their cost is really the issue?
I 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 = 440VDC
3: AC measurement of First Stage of DUT Power supply =~ 4.5VAC on meter, 4.6V on scope. This is 'normal' for this amp
4: I've had a request for a photo of my new Aneng V8 so here it is connected with a series de-coupling cap
5: DC measurement of Second Stage of DUT Power supply = 431VDC
6: 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 probe
Thanks again for all you valuable help
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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 voltage by showing a lightning sign on the display, their designs are much more concerned with other features.
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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. -
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?
Well, 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.
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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....
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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....
The 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
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I am still wondering which Brymen meters are AC-Coupled. Anyone have a clue?
I couldn't find a Brymen meter that has mVAC coupled, 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=bm857
That 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! -
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.
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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. -
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.
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Thanks for clearing that up. I should have asked that question from the start.
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I couldn't find a Brymen meter that has mVAC coupled, 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=bm857
That 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!
Really? That's great, didn't realize that the BM857 was in that price range. It looked expensive and scared me off, lol.
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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.