Author Topic: Are any of the Asian made Flukes AC-coupled?  (Read 6787 times)

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Offline ValverTopic starter

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Are any of the Asian made Flukes AC-coupled?
« on: February 12, 2019, 01:30:11 pm »
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.
 

Offline HKJ

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #1 on: February 12, 2019, 04:17:33 pm »
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.
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #2 on: February 12, 2019, 08:51:21 pm »
  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
 

Offline bc888

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #3 on: February 13, 2019, 01:56:51 am »
 

Offline Yansi

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #4 on: February 13, 2019, 02:04:58 am »
You can always use an external AC coupling capacitor.
 

Offline 001

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #5 on: February 13, 2019, 06:41:43 am »
   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.

Yea
it is hard to see fluctuations smallest than range resolution  :-//
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #6 on: February 13, 2019, 08:21:14 pm »
Ah, good, Thanks, for the link.
 

Online Fungus

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #7 on: February 13, 2019, 08:51:19 pm »
Hioki DT4282 will simultaneously display AC voltage and either the frequency or the DC offset value.

... none of these could measure any type of small AC signal whenever there's a DC bias higher than 20 volts.

It 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 is here
« Last Edit: February 13, 2019, 09:03:55 pm by Fungus »
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #8 on: February 13, 2019, 09:06:08 pm »
Hioki DT4282 will simultaneously display AC voltage and either the frequency or the DC offset value.

It has no limit on the DC bias voltage (other than the 1000V DC CAT rating).

There'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.
 

Online Fungus

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #9 on: February 13, 2019, 09:30:26 pm »
Hioki DT4282 will simultaneously display AC voltage and either the frequency or the DC offset value.

It has no limit on the DC bias voltage (other than the 1000V DC CAT rating).

There'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.

That's why I linked the manual, so you can read the specs.

Edit: In the manual it looks like 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.


« Last Edit: February 13, 2019, 09:50:51 pm by Fungus »
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #10 on: February 14, 2019, 12:39:44 am »
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.
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #11 on: February 14, 2019, 12:21:44 pm »
You can always use an external AC coupling capacitor.

Believe 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.   
 

Online Fungus

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #12 on: February 14, 2019, 01:39:31 pm »
Brymen BM869s might do it, but the specs are indecipherable (to me).

I'm sure #joeqsmith could tell us.

« Last Edit: February 14, 2019, 01:43:03 pm by Fungus »
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #13 on: February 14, 2019, 05:10:49 pm »
Brymen BM869s might do it, but the specs are indecipherable (to me).

I'm sure #joeqsmith could tell us.

The 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!

 
 

Offline schmitt trigger

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #14 on: February 14, 2019, 05:19:28 pm »
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.
 

Online joeqsmith

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #15 on: February 15, 2019, 12:34:21 am »
Brymen BM869s might do it, but the specs are indecipherable (to me).

I'm sure #joeqsmith could tell us.

It 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. 
« Last Edit: February 16, 2019, 04:24:40 pm by joeqsmith »
 
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Online joeqsmith

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #16 on: February 15, 2019, 12:15:12 pm »
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.   
 
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Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #17 on: February 16, 2019, 11:57:28 am »
Great, detailed info! This answers many questions I had concerning the BM869. Can't thank you enough for taking the time!
 

Online joeqsmith

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #18 on: February 16, 2019, 04:23:07 pm »
Great, detailed info! This answers many questions I had concerning the BM869. Can't thank you enough for taking the time!

Glad you found it helpful.  If there is something else you would like to know about the BM869s, feel free to ask.

Offline Kean

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #19 on: February 17, 2019, 11:48:26 pm »
Great, detailed info! This answers many questions I had concerning the BM869. Can't thank you enough for taking the time!

Glad you found it helpful.  If there is something else you would like to know about the BM869s, feel free to ask.

Joe, 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!
 

Online joeqsmith

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #20 on: February 18, 2019, 12:55:59 am »
Maybe Brymen will give me a raise.      .....   Let's see, that 10% of $0.   I'm rolling in it.   :-DD

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.

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #21 on: April 02, 2019, 06:35:06 pm »
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:

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.

So, 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 voltage
and 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/Brymen
TEL: +886 2 2226 3396 ext. 12
FAX: +886 2 2225 0025

___________________________________________

 :palm:  |O (Sigh) Maybe I should try a Ouija board ? Tarot?


 

Offline rsjsouza

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #22 on: April 04, 2019, 12:31:06 pm »
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.
« Last Edit: April 04, 2019, 12:38:49 pm by rsjsouza »
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 

Offline ValverTopic starter

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #23 on: April 04, 2019, 02:53:42 pm »
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.

Don'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.



 

Offline rsjsouza

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Re: Are any of the Asian made Flukes AC-coupled?
« Reply #24 on: April 04, 2019, 03:27:50 pm »
Perhaps try to bid on one?
eBay auction: #192874206504

I 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 400VDC handy (it is stored somewhere), but with 42VDC it shows:
100mVPP 1kHz sinewave on top of ~42VDC.

  • mVAC on U1282A - no external cap
  • mVDC on U1282A - no external cap. Input is not decoupled
  • mVAC on U1282A and BM857 - external 1nF cap
  • mVAC on U1282A and BM857 - no external cap. Input of BM857 is not decoupled
  • mVAC on U1282A and VAC+DC on BM857 - no external cap. Resolution on BM857 is not enough
  • mVAC on U1282A and VAC on BM857 - no external cap. Resolution on BM857 is enough to capture those mVAC
  • mVAC on U1273A and VAC on BM857 - no external cap. U1273A is decoupled and resolution on BM857 is enough to capture those mVAC
(the UT61E was useless above 5VDC of offset)
« Last Edit: April 04, 2019, 03:35:06 pm by rsjsouza »
Vbe - vídeo blog eletrônico http://videos.vbeletronico.com

Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 


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