Brymen BM869, short review (small update added 2013-01-19)

[marber]

I was looking at measuring ripple/noise of my power supply, and also used my Brymen BM869S in its 500 mV AC range - even though it's pretty limited in accuracy at high frequencies of course. For the 500mV AC range, the manual specifies accuracy of 2.5% + 40d between 20 kHz ~ 100 kHz.

The bench PSU was set to 3.000V DC, and connected to the multimeter using a coax BNC cable and a BNC-to-banana adapter. No load initially.

In mV AC mode, I noticed how it kept drifting up from single digit mV, steadily upwards and not settling on a value for a long while. As if a cap was being slowly charged. Eventually I let it sit for an hour, and it settled around 120 mV - while the linear PSU's ripple/noise is << 10mV as confirmed by other measurements. With a 50 ohm load (BNC terminator), it would rise at a faster rate. In it's AC+DC modes though, readings seemed far more accurate and stable.

Later I tested the 500mV AC range a bit more using a function generator. The BM869S is specified for 0.3% + 20d at 300 Hz ~ 5 kHz in this range. A 1 kHz sine wave of 100-500 mV RMS seemed to result in reasonably accurate values, matching my other meters. However introducing more than about 1V of DC offset seems to completely throw it off, and the values become wildly inaccurate beyond its already wide specs. In the 5V AC range it seems fine.

The Hz secondary display in the mV AC range cut out much earlier, basically as soon as the DC offset + amplitude implies there are no 0V crossings anymore.

So is that range not really AC coupled? Is it just my meter (defect) or do other BM869s behave the same?

[Wytnucls]

To measure Vrms accurately (2.5%+40), the value should be above 10% of range (ie 50mV in this case). True RMS converter limitation.
Below 5% of range, no measurement is valid. Between 5% and 10%, add another 80 digits (2.5%+120). Your 10mV is well below the lower limit.

With an offset, some meters need to have Vpeak stay within the selected range and have a zero crossing for frequency.

I don't think there is anything wrong with your meter.

[netman]

Here's that backlight of the 857s.
Note the display does have more contrast than that when viewing at the correct angle.
Might re-shoot that pic to check the difference.

Viewing angle on mine is pretty bad, I pretty much thought I had a defective unit but judging from the photo it's standard, that's about what mine looks like. Does yours also fade to unreadable if you view from above even just a bit over 90 degrees (with the backlight on)?

[pascal_sweden]

I really wonder why it is that hard for a manufacturer to source a display that works under all viewing angles, implement that display in their entire product line, and stick with that display once and for all!!!

Cheap brands like Uni-T, Vichy, have some models where the display has an excellent viewing angle.
So it can definitely not be related to a cost issue, if the cheap brands can do it.

It's just a matter of being consistent. The cheap brands should start using that "good display" in their entire product line.

And the more expensive brands like Brymen, should do the same, under the motto, "whatever the cheap brands can, we can, and from now on we are going to be consistent once and for all, and no longer mess around with randomly selecting a display when designing a new multimeter, and after just hope the best for it, and say sorry if it has a bad viewing angle, and realize it's too late to change!"

I really hope Brymen is reading along in this thread. Uni-T and Vichy might read along as well

To Brymen, Uni-T, Vichy and all the other manufacturers of multimeters (including Fluke and the other big guys): get your act together on displays, and only take displays with excellent viewing angles

And no, this issue is not only a concern for display afficionados, to use Dave's words
It's a general concern, that affects all users! Viewing angles are so important for test gear!

[chickenHeadKnob]

I have a BM857a that has the old crappy backlight. With the backlight off the display is very crisp and black over a fairly wide range. It makes me think the quality control has been slipping at the lcd manufacturer since the s models. Desktop displays have a specification called design eye center which is the optimum location for the viewers eye ball. I think part of the annoyance of the Brymens is that their optimum design eye center is too low, meaning it is overly optimized for handheld use where you look down at the meter at an acute angle with the meter held at  chest height.  if they had made the central angle closer to 90 degrees we wouldn't notice so much with bench top use.

[netman]

I have a BM857a that has the old crappy backlight. With the backlight off the display is very crisp and black over a fairly wide range. It makes me think the quality control has been slipping at the lcd manufacturer since the s models. Desktop displays have a specification called design eye center which is the optimum location for the viewers eye ball. I think part of the annoyance of the Brymens is that their optimum design eye center is too low, meaning it is overly optimized for handheld use where you look down at the meter at an acute angle with the meter held at  chest height.  if they had made the central angle closer to 90 degrees we wouldn't notice so much with bench top use.

A lousy backlight actually would be better than the -s one seen from above, with backlight off it's somewhat usable from that angle but looks blurry and dim.

[CustomEngineerer]

I really wonder why it is that hard for a manufacturer to source a display that works under all viewing angles, implement that display in their entire product line, and stick with that display once and for all!!!

Cheap brands like Uni-T, Vichy, have some models where the display has an excellent viewing angle.
So it can definitely not be related to a cost issue, if the cheap brands can do it.

It's just a matter of being consistent. The cheap brands should start using that "good display" in their entire product line.

And the more expensive brands like Brymen, should do the same, under the motto, "whatever the cheap brands can, we can, and from now on we are going to be consistent once and for all, and no longer mess around with randomly selecting a display when designing a new multimeter, and after just hope the best for it, and say sorry if it has a bad viewing angle, and realize it's too late to change!"

I really hope Brymen is reading along in this thread. Uni-T and Vichy might read along as well

To Brymen, Uni-T, Vichy and all the other manufacturers of multimeters (including Fluke and the other big guys): get your act together on displays, and only take displays with excellent viewing angles

And no, this issue is not only a concern for display afficionados, to use Dave's words
It's a general concern, that affects all users! Viewing angles are so important for test gear!

Uni-t and Brymen both make cheap and not so cheap meters. They both cover the same price ranges, though Uni-T has several meters that are more expensive than the most expensive Brymen's that I can find, and several meters that are cheaper than the cheapest Brymen's. But for the most part they are equivalent price wise.

[cluca1969]

I read many reviews about BRYMEN 867 and 869s but none have fully clarified me very good so I would need some advice from you, what to choose between a Brymen 867 or a Brymen 869s ?
Excluding the functions of double TEMP and VFD, which I do not need right now.
There is so much difference in accuracy between BM867 - 0,003 vs. BM869s - 0,002 ?
I already have one FLUKE 185 but I want one DMM with 500,000 counts.

[chronos42]

Hi,

beside of the 0.02% accuracy the 869s has a different and better AC part, so for me this was the main reason to buy this one.
The 500000 counts seems impressive, but it is not in reality. It is only usefull if you want to see small voltage drifting. But it is still a 0.02% handheld meter, not a 500000 digit lab grade meter.
Beside of this, the 876s is one of the best meter you can get fot this price.

[cluca1969]

Hi chronos42,
Thank you very much for useful information but I'm still undecided who to buy it, I need strong reasons to choose the best one.
I've seen some tests on: http://www.118volt.it/en/brymen-bm869-bm867-batch-calibration-check/ and I started to have some doubts about the BM896s.
I think the difference between them is very relevant.

[Lightages]

All of the meters shown are within specification. The BM869S has an accuracy specification of 0.02% +2D. This means that a 5V test source could be displayed as high as 5.0012V and as low as 4.9988V

The maximum error demonstrated in the pictures is 0.008% These images are not reasons to not want to buy a BM869S. If you want a meter that reads better than 0.01% you should be using a bench top meter that is left running all the time to keep it stable. You might have other reasons that you don't want to buy a BM869S but these images actually show that the meters meet their specifications.

Edit: I can even quote the author of the link you posted "As you can see all meters are well within specs and the older meter does not exhibit any noticeable drift from the new multimeters.". This is all good news in favor of the BM869S, not against it.  What is the problem? 

[cluca1969]

Hi Lightages,

Thank you very much for your answer.
My problem is, and here I am not strictly referring to BM867 & 869s.
I have a few Reference Voltage 2.5V 5V 7.5V 10V and from time to time I like to check my multimeters.
I have some DMM the oldest is 24 years old (HC-81 and DM27).
1. HC-81 - powered 9V
2. DM27 - powered 2 x AAA
3. UT70B - powered 9V
4. Fluke 185 - powered 2 x AA
5. AN8008 - powered 2 x AAA
6. Fluke 17B+ - powered 2 AA

So, for me it is hard to accept that a DMM (AN8008) of $17 is more accurate than a DMM that costs $250 like BM869s.
I hope you understand my concern over the accuracy versus the money spent on them regardless of brand.

[Lightages]

So, for me it is hard to accept that a DMM (AN8008) of $17 is more accurate than a DMM that costs $250 like BM869s.
I hope you understand my concern over the accuracy versus the money spent on them regardless of brand.

How can you know that the AN8008 is more accurate when it could be out as much as 0.02% before you could see that difference? It does not have the resolution to show it. Even if it shows 5.000V with a 5V source it could be out as far as 0.02% before the last digit will change. The BM869S meters shown in the picture clearly demonstrate their accuracy better than 0.01%. The AN8008 can't resolve that difference. You are a little obsessed with a clean all X.0000 display IMHO.

[cluca1969]

You're right, maybe it's an obsession for me to have an almost perfect DMM, may be an benchtop DMM.

[IanB]

You're right, maybe it's an obsession for me to have an almost perfect DMM, may be an benchtop DMM.

I understand the obsession with getting a "perfect" reading. One way to do this, when you do get a perfect reading, is to take a picture of it. Then in future when you get a need to see perfection you can just refer back to the picture. Like this:

[cluca1969]

Hi IanB,

Yes, that's what I wanted to talk about.
I will keep the pictures from you in my database and I compare them to other next situations.

[eztestmeasure]

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