Decent benchtop multimeter for beginner?

[skander36]

However, since the meter is 6 years old, it's not under warranty anyway. Maybe it would be better to let an independent lab calibrate / adjust the meter?

This is not gonna happen. I already paid 200E plus shipping to Germany in the hope that this meter will came close to the other two DMM's. If I'm not getting money from DMM I will not calibrate it again.
It had this behavior from the first day when it arrived from calibration.
It will stabilize itself, as I said after 3-4 hours, when I can generate a calibration file to use it as user calibration, but at this interval is no use for me, as I have the other two DMM's that can stabilize faster.

[bdunham7]

It had this behavior from the first day when it arrived from calibration.

Any idea what its behavior or measurements were before calibration?

[skander36]

It had this behavior from the first day when it arrived from calibration.

Any idea what its behavior or measurements were before calibration?

About the same curve drift. This was the reason for sending to calibration.

[KungFuJosh]

You posted a screenshot in another thread showing your SDM3065X with about 2ppm p-p noise over a 30-minute period.  What was it measuring on cold power-up with the reference warmed up?  Do you get anywhere near as much power-up settling as skander36?

Wasn't that 27ppm noise?

I didn't test cold power up at all since it's sort of pointless. Ignoring warmup times for both the ref and the meter doesn't make any sense to me.

I could try another time if you think it matters, but the meter's been on for 7 hours so far today, so no cold start info for a while.

[KungFuJosh]

This is not gonna happen. I already paid 200E plus shipping to Germany in the hope that this meter will came close to the other two DMM's. If I'm not getting money from DMM I will not calibrate it again.
It had this behavior from the first day when it arrived from calibration.
It will stabilize itself, as I said after 3-4 hours, when I can generate a calibration file to use it as user calibration, but at this interval is no use for me, as I have the other two DMM's that can stabilize faster.

Understandable, and that makes sense. In the other thread Defpom said:

It is FAIRLY settled after an hour, it is still warming up for about 4 hours, after that although there is still some movement but it is small.

So I posted my first 4 hours in that thread, then I reset the data, and I'm going to post the following 4 hours when it's done. P-P was 0.000042 for the first 4 hours, and then after two hours on the new test it's currently holding at 0.000030 P-P.

I don't know how many hours of on-time your SDM has had, but I assume more than mine. I think mine is still in the low hundreds of hours at most.

You could always just leave your meter powered on forever. Then problem solved. 😉

If you feel like doing the same test as me, I would love to see that info. 1 hour warmup, 4 hours tracked, then reset data and continue tracking for 4 hours. I want to see how your PP compares. 🤣🤣🤣🤣🤣

[skander36]

...

If you feel like doing the same test as me, I would love to see that info. 1 hour warmup, 4 hours tracked, then reset data and continue tracking for 4 hours. I want to see how your PP compares. 🤣🤣🤣🤣🤣

This doesn't make any sense to me. My point was a compare between three different DMM's.

[G0HZU]

Maybe a blasphemy question, but what do you need 6-digit absolute accuracy for - except for calibrating other instruments?

All validation/qualification labs I know had basic requirements of 0.1% or in rare cases 0.05%. If your meter should be one order of magnitude better than your specification you get to 0.005% - these are 4 1/2 digits.

Of course you can use 7 or more digits for relative purposes. Seeing small changes also over a large timespan is a great feature, so the instrument should have sufficient stability. From a pragmatic point of view this stability can also be ensured by tracking an external standard instead of going through the exhaustive and expensive complete calibration process.

What are real life applications for 6 digit absolute accuracy and not only stability? I´m curious.

Few professional people will need the absolute accuracy, but because DVM technology has been 'boringly brilliant' for several decades now, the internal reference accuracy and stability justifies 6.5 digits or maybe more for a decent bench multimeter.

In my experience, 6.5 digit meters generally offer other features making them very attractive for professional ATE systems. They offer fast read rates and various inbuilt math functions and they offer GPIB and/or USB and/or LAN interfaces.

In all my years at work, I have never seen any engineer get excited when a decent DMM was returned from calibration. Also, I don't think I've ever seen an engineer check two 6.5 digit DMMs against each other in the way many hobbyists do obsessively. Many of them seem to progress to obsessing over state of the art voltage references and calibrators.

Don't ask me what they think they need this stuff for, but in other hobbies there will always be people who want either the titanium/platinum/silver/gold version of whatever widget(s) the hobby demands. I think it's partly a status thing, partly a FOMO thing and partly an OCD thing.

[KungFuJosh]

...

If you feel like doing the same test as me, I would love to see that info. 1 hour warmup, 4 hours tracked, then reset data and continue tracking for 4 hours. I want to see how your PP compares. 🤣🤣🤣🤣🤣

This doesn't make any sense to me. My point was a compare between three different DMM's.

You compared the 3 devices from cold start. I'm curious about the actual stability of your DMM, which requires warmup time first. You could still measure all 3 if you want to compare.

Comparing between 3 DMMs is fun, but if you want to see if there's an actual problem with one of them, you have to test it properly.

I just saw this post:

Josh, you write a lot of personal assumptions (AKA BS).

The point is not he performance but a comparison between them.
The meters was tested in the same time. As KS and KT was able to keep a reasonable reading, so Siglent should stay aside. If not in my opinion is inferior. You may have your personal opinion of course.
-No, none of the meters doesn't show the actual value of the reference, they can't as they are 6.5 digit and this value is from a 3458A used for calibration. Actually the real value is 10.000001 after adjustement. 10.000005 was before (after 1 year and 8 month from fabrication) see picture from adjustement.
The drift will eventually stop after 3 about hours - see attached.

That's what I correctly assumed, an 8.5 digit meter. That number also has to take into account temperature and humidity. Did you when you tested your 3 meters? You will never match that number otherwise.

Your results are BS if you wanted to test or compare anything besides cold start drift. It's simply not accurate to claim you have a problem based on cold start. That's not an opinion or an assumption. Every device requires warmup time to meet specs.

I'm not saying the Siglent isn't inferior to the other two meters. I would love to have a DMM6500 if I could afford it. That doesn't make my Siglent a piece of crap; it's just not as nice as the meter that costs twice as much. I'm not shocked by that.

[bdunham7]

Wasn't that 27ppm noise?

No, that would be terrible.  27µV is what is displayed in the box, that's 2.7ppm. 

I didn't test cold power up at all since it's sort of pointless. Ignoring warmup times for both the ref and the meter doesn't make any sense to me.

First, characterizing your meter so you know how it behaves can be helpful because then you'll know how long you have to let it warm up before you can get a certain level of accuracy.  Second, the power-on settling data can give you some idea of what the TC of the unit will be like.  An hour is an arbitrary time, regardless of whether or not it appears in a manual.  You might discover that for all practical purposes your meter is spot-on after 5 minutes or you might find that it is not even well within spec until an hour goes by.  Either result may be technically acceptable and no cause for complaint, but it is still useful to know.

[KungFuJosh]

I suppose I should be less lazy. I might have been using an online calculator that said 0.000027 = 27ppm. Ok, 27uV is 2.7ppm. Cool. I assume there's some context as to why there's a discrepancy.

Fair enough. I often use my DMM with 1 minute of warmup, I haven't had any issues. I also don't usually test anything that cares about uV resolution.

Tomorrow I'll test both from cold start. Or should I warm up the ref first, to separate that? It makes sense to me to warm up the ref first remove the ref's drift from the test.

ETA: removing the ref's drift might prove difficult if I can't keep my room consistent as my other test showed (even if it was obvious).

Thanks,
Josh

[bdunham7]

Tomorrow I'll test both from cold start. Or should I warm up the ref first, to separate that? It makes sense to me to warm up the ref first remove the ref's drift from the test.

Ideally you'd do it both ways--with the ref warmed up and meter cold then vice versa.  But try it the first way first.  IDK what I'd do if I had to shut my power off nightly--I have multiple references and instruments that stay on for months on end.  I may have missed it if you said earlier, but what is your reference?

[skander36]

That's what I correctly assumed, an 8.5 digit meter. That number also has to take into account temperature and humidity. Did you when you tested your 3 meters? You will never match that number otherwise.

Your results are BS if you wanted to test or compare anything besides cold start drift. It's simply not accurate to claim you have a problem based on cold start. That's not an opinion or an assumption. Every device requires warmup time to meet specs.

I'm not saying the Siglent isn't inferior to the other two meters. I would love to have a DMM6500 if I could afford it. That doesn't make my Siglent a piece of crap; it's just not as nice as the meter that costs twice as much. I'm not shocked by that.

Actually you said that

...

I don't agree, and I won't assume anything, because the stated value of the reference is very likely BS.

I proved that the referece value is not BS.

The other meters can provide a trusty reading no mater the conditions, while the Siglent not.  This is the idea.

[tautech]

That's what I correctly assumed, an 8.5 digit meter. That number also has to take into account temperature and humidity. Did you when you tested your 3 meters? You will never match that number otherwise.

Your results are BS if you wanted to test or compare anything besides cold start drift. It's simply not accurate to claim you have a problem based on cold start. That's not an opinion or an assumption. Every device requires warmup time to meet specs.

I'm not saying the Siglent isn't inferior to the other two meters. I would love to have a DMM6500 if I could afford it. That doesn't make my Siglent a piece of crap; it's just not as nice as the meter that costs twice as much. I'm not shocked by that.

Actually you said that

...

I don't agree, and I won't assume anything, because the stated value of the reference is very likely BS.

I proved that the referece value is not BS.

The other meters can provide a trusty reading no mater the conditions, while the my Siglent not.  This is the idea.

FTFY

I have no idea why yours seems to be a problem child and even though you've had it recently checked it drifts outta spec. 

[2N3055]

...The other meters can provide a trusty reading no mater the conditions.....

I presume what you wanted to say, but this statement is highly doubtful..

I'm sure I could provide conditions to make them show numbers highly different from what you expect...

[KungFuJosh]

Ideally you'd do it both ways--with the ref warmed up and meter cold then vice versa.  But try it the first way first.  IDK what I'd do if I had to shut my power off nightly--I have multiple references and instruments that stay on for months on end.  I may have missed it if you said earlier, but what is your reference?

I attached a photo from the aliexpress listing for the ref I have. The stated values are (surprisingly) not the same as the piece of paper that came with mine. 😉

I have the ref warming up now, I'll turn on the meter soon and do the cold start test.

If I had solar I might leave stuff on, but my electric bills are already way too high as it is.

[robert.rozee]

I attached a photo from the aliexpress listing for the ref I have [...]

 

[nctnico]

I'm wondering how they measured the resistors on that board so accurately...  But they don't look like low tempco, low drift resistors anyway. Also, the AD584 isn't the best reference out there. There are so many better choices.

[KungFuJosh]

Make fun all you want, it's pretty damn good for $20. 

[Aldo22]

Make fun all you want, it's pretty damn good for $20. 

I ordered something similar for CHF 6.
Apparently it uses an AD584L which is supposed to be reasonably accurate (+- 5mV @ 10V).

According to the pictures in the comments, it's measured with a 34401A.


Let's see, I don't have it yet.
For this price you can give it a try.
It's just for fun, I only have an AN870.

[bdunham7]

I have the ref warming up now, I'll turn on the meter soon and do the cold start test.

The TC of that reference is probably not great, so keeping it at a constant temperature is more important than a long warmup.  It's still an experiment worth doing, as well as the inverse with a stabilized meter.  How good is the temperature stability of your lab/room/bench?

[KungFuJosh]

Make fun all you want, it's pretty damn good for $20. 

I ordered something similar for CHF 6.
Apparently it uses an AD584L which is supposed to be reasonably accurate (+- 5mV @ 10V).

According to the pictures in the comments, it's measured with a 34401A.

Let's see, I don't have it yet.
For this price you can give it a try.
It's just for fun, I only have an AN870.

I have a couple others similar to those (maybe the same one also?). They give the same printout with every one of them, no value changes. That's why I commented about the values for mine not being the same as the photo, as that's rare on aliexpress.

I don't remember who, but another member on here told me about the purple one I ordered. It's the best I've seen of these cheaper references.

[Aldo22]

I have a couple others similar to those (maybe the same one also?). They give the same printout with every one of them, no value changes. That's why I commented about the values for mine not being the same as the photo, as that's rare on aliexpress.

I don't remember who, but another member on here told me about the purple one I ordered. It's the best I've seen of these cheaper references.

I also have my doubts about these "individual" measurements.
But the AD584L is supposed to be a bit better than the "J" or "K" variants.
Should arrive next week.

[KungFuJosh]

I also have my doubts about these "individual" measurements.
But the AD584L is supposed to be a bit better than the "J" or "K" variants.
Should arrive next week.

Most of the ones that I bought was advertised as AD584L. 🤷

I also got a couple from Amazon and eBay.

[Aldo22]

Most of the ones that I bought was advertised as AD584L. 🤷

OK, but if it does what it promises, it's good enough for my purpose (+- 5mV @10V), even if it wasn't measured individually.
That's what I meant.

[KungFuJosh]

Most of the ones that I bought was advertised as AD584L. 🤷

OK, but if it does what it promises, it's good enough for my purpose (+- 5mV @10V), even if it wasn't measured individually.
That's what I meant.

Oh, I'm not arguing with you. I agree, they're generally good enough for my purposed too, but the purple one has been the best (living up to the claims etc).

Some people will obviously laugh at these references, but if they want to buy us $400 references, that would be fine with me too. 😉

The seller I got the purple ref from has these now instead: https://www.aliexpress.us/item/3256806626314478.html

I guess they ran out of the 584Ls. I have no idea if those are any good, but he also has some other interesting ref boards for L, C, R individually.