Look at the BM325 AC voltage RMS spec. Its accuracy is only specified up to 800Hz. Above 800Hz you start wondering. My significantly older Fluke 76 has a bit wider AC frequency range, slightly better ACV RMS accuracy and 3x more accurate frequency counter.
PSU work:
Not suitable if you are measuring a switching PSU output ripple where switching frequency can go above 1MHz. The low AC ripple reading you will be getting from the BM325 will be too optimistic even for switchers that operate in the lower kHz range since you have the 800Hz accuracy limit.
Audio work:
You can't even measure 1kHz accurately. Why bother? You are restricted with 800Hz test tones and below where ACV RMS accuracy is at 2% + 3 digits.
The BM325 built-in frequency counter has a 300ppm + 2 digits accuracy. Yay!
It's an influencer-advertised product. Buy a product that sells by itself instead.
I’m a cheap meter guy but it’ll be interesting to see the response of more experienced DIY folks. OTOH I did buy a Fluke this year after a cheap DMM started getting wonky after six months of field use on low voltage systems. Of course I wouldn’t touch anything more than household voltage with a cheap meter...
Huh. If that is the case then go for the one with the most useless posts.
Quantity over quality.
So the bm867 would be a better choice? I think the extra bandwidth is useless and not worth the extra of the bm869.
Which one would you recommend? I am in Europe and the BMs are way cheaper for equivalent performance.
Hi,
which 'reasonable' Fluke could that be?
The BM867s compares favourably to the Fluke 289, which costs about 4-5 times as much.
jauu
Calvin
which 'reasonable' Fluke could that be?
The BM867s compares favourably to the Fluke 289, which costs about 4-5 times as much.
jauu
Calvin
Yes, the BM867 has better ACV RMS accuracy than the BM325 according to the spec sheet.
You define the bandwidth and accuracy requirements first then look around for what is available, new or used. Learn to read the specifications and make an informed decision based on your actual need and budget.
Hi,
the 867 is really fast.
The Trendchart display updates very rapidly.
With the Hold and/or Crest function You can catch very short pulses/spikes on a dc voltage.
The amplitude response of the rms measurement peaks at the upper end .... the bandwidth varys with the amplitude of the measured signal/measurement range ... so take care when trying to 'measure' the audio amplitude response of a device.
For audio measurements the 867 is far more useful than the 235 .... but sooner or later You'd probabely be better off with a dedicated audio analyzer tool.
jauu
Calvin
the 867 is really fast.
The Trendchart display updates very rapidly.
With the Hold and/or Crest function You can catch very short pulses/spikes on a dc voltage.
The amplitude response of the rms measurement peaks at the upper end .... the bandwidth varys with the amplitude of the measured signal/measurement range ... so take care when trying to 'measure' the audio amplitude response of a device.
For audio measurements the 867 is far more useful than the 235 .... but sooner or later You'd probabely be better off with a dedicated audio analyzer tool.
jauu
Calvin
DMMs are great things. You should have *several*. To monitor several points at once, to cross-check one against the other, to learn which one does what better.
Affordable DMMs are NOT aimed at wide-band AC accuracy. You can try to do a calibration curve, but the "true RMS" (IMHO a useless feature for us) may also vary with level: flat to 4KHz at 1V but sagged-off at 400Hz at 0.1V (for example). The "not RMS" (averaging) meters are slightly less liable to bad treble, but I have seen some that sucked.
For *accurate* AC Volts you want a reliable ACVM. The most basic is an old-school VTVM: the passive rectifier in these is scaled OK from 0.2V to 1.5V or ranged (which covers line-level up) and for impedances under 10K will be flat far beyond 20KHz. Most get saggy below 20Hz- you can upsize the input caps, I had mine down to 0.05Hz but the settling time was "coffee break".
Because many eBay VTVMs need more repair than they are worth, you should look for the H-P and similar ACVMs, transistorized. Descendants of the old Ballantine ACVM which is now so old that repairs are for geeks only.
Affordable DMMs are NOT aimed at wide-band AC accuracy. You can try to do a calibration curve, but the "true RMS" (IMHO a useless feature for us) may also vary with level: flat to 4KHz at 1V but sagged-off at 400Hz at 0.1V (for example). The "not RMS" (averaging) meters are slightly less liable to bad treble, but I have seen some that sucked.
For *accurate* AC Volts you want a reliable ACVM. The most basic is an old-school VTVM: the passive rectifier in these is scaled OK from 0.2V to 1.5V or ranged (which covers line-level up) and for impedances under 10K will be flat far beyond 20KHz. Most get saggy below 20Hz- you can upsize the input caps, I had mine down to 0.05Hz but the settling time was "coffee break".
Because many eBay VTVMs need more repair than they are worth, you should look for the H-P and similar ACVMs, transistorized. Descendants of the old Ballantine ACVM which is now so old that repairs are for geeks only.
I am also considering a Brymen BM807s right now, since Brymen is much cheaper than Fluke's models with similar accuracy. If Brymen's are as reliable and durable, I would go for them any time.
The EVblog guy and forum seem to be in the "business" of reviewing test gear. Browsing there may tell you much more, much faster, than random anecdotes here.
Brymen multimeters review again BM805 and BM807 - Page 1
Test Equipment - Page 1
Brymen multimeters review again BM805 and BM807 - Page 1
Test Equipment - Page 1
Thanks. Reviews usually tells about functionality and accuracy. It won't tell anything about durability and reliability (drifts, failures, etc). You have to use meters for a few months or maybe years to draw conclusion.
If reliabilty and durability is not an issue, any cheap handheld meters + dedicated more advanced / professional meters would be the way to go.
In 2017, an eevblog mentioned a small issue with the by professionals and diy’ers highly regarded Brymen, as quoted below. The quote suggests the issue probably was inherent to many multimeters:
Some problems with my Brymen BM869S - Page 1
“TRMS converters are not very good at measuring AC below 5% of the range. The Brymen seems to be quite sensitive. First the biggest weak point: The mV AC range. What is wrong with this? At a first glance there is nothing wrong. But if you take a closer look there is a big problem. The meter cannot handle a mV AC together with a high DC. In the V range there are no problems, it can handle AC, DC, AC+DC in any combination without any Problems, this was shown in several reviews. But if I set the meter to mV AC and connect it to a DC source I can see a problem. The meter must show 0V AC, Independent from the DC. Every meter I had tested did this in the AC mV range, even with high DC offsets . . . “
Several recent multimeters seem to have addressed this issue, or did they? For instance, the datasheet of a Chauvin Arnoux C.A 5275 and C.A 5277 multimeter mentions – next to the usual Vac, Vdc – also ‘Vac + Vdc’ resp. ‘Aac + Adc’ as a separate measurement setting to measure both simultaneously.
http://www.chauvin-arnoux.com.cn/sites/default/files/User Guide CA5277 EN.PDF
Another example is the Metrahit Base / Pro / Tech multimeter series of Gossen Metrawatt.
The multimeters mentioned are in the higher price segment for a hobby lab, and may offer functions far exceeding the average need in a diy lab. Still some questions come to mind:
- Is this indeed a new development in measurement technique?
- If so, are there any examples of multimeters in the lower price segment that already incorporate this feature?
- any experiences?
What do you think?
Some problems with my Brymen BM869S - Page 1
“TRMS converters are not very good at measuring AC below 5% of the range. The Brymen seems to be quite sensitive. First the biggest weak point: The mV AC range. What is wrong with this? At a first glance there is nothing wrong. But if you take a closer look there is a big problem. The meter cannot handle a mV AC together with a high DC. In the V range there are no problems, it can handle AC, DC, AC+DC in any combination without any Problems, this was shown in several reviews. But if I set the meter to mV AC and connect it to a DC source I can see a problem. The meter must show 0V AC, Independent from the DC. Every meter I had tested did this in the AC mV range, even with high DC offsets . . . “
Several recent multimeters seem to have addressed this issue, or did they? For instance, the datasheet of a Chauvin Arnoux C.A 5275 and C.A 5277 multimeter mentions – next to the usual Vac, Vdc – also ‘Vac + Vdc’ resp. ‘Aac + Adc’ as a separate measurement setting to measure both simultaneously.
http://www.chauvin-arnoux.com.cn/sites/default/files/User Guide CA5277 EN.PDF
Another example is the Metrahit Base / Pro / Tech multimeter series of Gossen Metrawatt.
The multimeters mentioned are in the higher price segment for a hobby lab, and may offer functions far exceeding the average need in a diy lab. Still some questions come to mind:
- Is this indeed a new development in measurement technique?
- If so, are there any examples of multimeters in the lower price segment that already incorporate this feature?
- any experiences?
What do you think?
Last edited:
Measuring a combination of AC + DC accurately is a complex subject. And not often useful.
Measuring AC itself is a very involved subject. RMS VS Average responding RMS reading vs peak etc. Accuracy also becomes quite the issue. Expect maybe .5% low frequency but 3% at 100KHz would be good. And that average reading instrument will lie on a distorted waveform (e.g. AC charging voltage) however a DSO will answer all the questions and can be pretty cheap.
Measuring AC itself is a very involved subject. RMS VS Average responding RMS reading vs peak etc. Accuracy also becomes quite the issue. Expect maybe .5% low frequency but 3% at 100KHz would be good. And that average reading instrument will lie on a distorted waveform (e.g. AC charging voltage) however a DSO will answer all the questions and can be pretty cheap.
Yeah, other people have corroborated the excellent performance of BM869 and compared it to the top Fluke and Keysight meters favorably. Including teardowns for safety.
I have a Keysight U1273A, Fluke 8060A, and BM235, and the Brymen is really pretty good for the price. I suspect most of their products are competitive from what I've seen.
If you have to buy one dvm, buy a good one, and you can go wrong with Fluke. there are a lot available used on ebay, they are built to last a lifetime, keep their accuracy, meet their specs, and are safe, especially on HV if you work on tubes. I bought an expensive one 20 years ago and it is still my most usefull piece of test gear. Btw worked for 10 years in a calibration lab, and Fluke were some of the best!
SB
SB