Aneng SZ20 25,000 count, 1uV, 10nA, 20A

[Paul T]

Has anyone ever noticed that the ZT-225 is actually incorrectly labeled? 
It is not a 25000 counts but a 25499 counts meter. 
This is of course not a big plus, but it just means that the 2.5V of an AD584L voltage reference is displayed with 5 digits, even if the measurement is slightly above 2.5V.
The AN870 strictly stops at 19999 and does not display e.g. 2.0000V.

I noticed the same thing with the ANENG SZ20 while compiling resistance range data.  It's not limited by segments available in the screen display. 

I have a few meters which promise fewer counts than the capacitance range actually reports.

[Paul T]

@Aldo22,

What is your findings with accuracy when the meter ranges to the next level of counts?  I noticed at the upper level of precision on resistance there is a shift in the actual value, beyond the precision.  Perhaps the high precision result at the upper end of the range is less trustworthy than the lower count result along the next range. It may also depend on the value of physical resistors if they are using any external ladder.

In theory, you change the range and the extra digit gets rounded, but that seldom seems to be the case.

[Aldo22]

@Aldo22,

What is your findings with accuracy when the meter ranges to the next level of counts?  I noticed at the upper level of precision on resistance there is a shift in the actual value, beyond the precision.  Perhaps the high precision result at the upper end of the range is less trustworthy than the lower count result along the next range. It may also depend on the value of physical resistors if they are using any external ladder.

In theory, you change the range and the extra digit gets rounded, but that seldom seems to be the case.

I'm not quite sure if I understand you correctly.
Is that what you mean?
2.5488V
Increase source by 1mV =
2.550V

That looks right to me.

What I sometimes wonder about is the difference between the VDC setting and the VDC AC+DC setting.
There are some deviations in the mV range here.
Well, VDC AC+DC has a different accuracy: ±(0.5%+3).
I think it is within the tolerance limits.

[Paul T]

The range misalignment is likely more pronounced on functions which carry a larger tolerance percentage.

[mwb1100]

Has anyone ever noticed that the ZT-225 is actually incorrectly labeled? 
It is not a 25000 counts but a 25499 counts meter. 

It's not uncommon for meters to go a bit above their specified count.

It's also not uncommon for them to switch ranges right when they reach the specified count.

[Aldo22]

It's not uncommon for meters to go a bit above their specified count.

It's also not uncommon for them to switch ranges right when they reach the specified count.

Yes, I think you can identify this by whether a DMM is labeled with x999 counts or x000 counts. Is that correct?
Examples from my DMMs:

AN8008: 9999 counts. No tolerance.
AN870: 19999 counts. No tolerance.
ZT-225: 25000 counts. Up to 25499
UT123: 4000 counts. Up to 4099.

[Aldo22]

The range misalignment is likely more pronounced on functions which carry a larger tolerance percentage.

I don't really see a problem here.



Sure, it could round up to 2.546k, but the specification is ±(0.2%+3) for resistance.
So plus or minus 3 at the last digit is allowed.

[Paul T]

Thanks Aldo22!  Hold onto your unit, it's really good.  Not sure if you got a gem, or if the ZOYI is better than the ANENG.  Yours works better than mine in AC+DC volts and also keeping accuracy when range switching.

[Aldo22]

Yours works better than mine in AC+DC volts

AC measurement can be quite tricky due to the limited bandwidth.
With a square wave it quickly becomes inaccurate, probably due to the slew rate?

An oscilloscope is better suited for this.

[Paul T]

I should have said DCV is more consistent on your device when measuring in the AC+DC setting, as we noted earlier in the thread.

[Aldo22]

Not sure if you got a gem, or if the ZOYI is better than the ANENG. 

I suppose you have the same HW version?

[Paul T]

I have not unscrewed my aneng yet.  Just got it a couple months ago.

Darren Walker has the same version as you it appears.  His review is from a year ago.

https://youtu.be/W9UhA54JboA?si=QM6MkHwrGrzkodXS&t=1029

[Paul T]

With additional testing, it seems the manual range transition has negligible offset.

Voltage was perfect across 0.025, 0.25, 2.5, 25 VDC

Resistance was as follows (decade resistor board)
250.08 to 0.2503k
2.4936k to 02.493k
24.965k to 024.97k
249.28k to 0.2483m

[Aldo22]

2.4936k to 02.593k

Hmm, but these two values are probably out of specification of ±(0.2%+3).
Are you sure this measurement is correct?

[Paul T]

I had a lot of texts coming in when I was typing this in!    It’s a typo.

[Aldo22]

I had a lot of texts coming in when I was typing this in!    It’s a typo.

Then it looks good! 
Do the resistors have 1% accuracy?

[Paul T]

Yes it is the 8 decade resistance board from AliExpress with 1% resistors.

[Cosmic_Starlight]

i really dont have much idea of what am doing, much less have any sort of trustworthy reference values (closest is the 1% resistors on the gm328)

anyways i tried to repeat aldo's test somewhat haphazardly by putting in series 2 1k resistors, 2 240 ohms and two 47 ohms resistors and the difference between switching ranges seemed to be negligible

EDIT** holy moly the image resolution was huge for some reason sorry anyone that had to see that

also i tried comparing measurements between the ac volts, dc volts and the ac+dc option

a brand new AA alkaline battery on dcv reads
1.6238v

on ac+dc it reads
1.6246-1.6247

tried ac from mains and it seemed ac+dc read about 0.1-0.2v higher but mains is too unstable to know for sure

also tried ac volts from a phone generating a 1khz sine wave audio signal from rca jacks and
on acv it reads 0.1612v

on ac+dc it reads
0.1613v

i guess it makes sense ac+dc gives slightly different values since thats what the manual specifies

so idk if am good or not, coincidentally i have the exact same revision as aldo's

225.v1.0.2022809.

i wouldnt be surprised is there isnt any other revision