Zoyi ZT-MD1 - new LCR Tweezers

[slavoy]

I don't see any detailed specs yet. Just this short info, and the price $48

https://thedmm.com/shop/zt-md1/

[TheDefpom]

They are supposed to be sending me one to review... so watch this space :-)

[Phil1977]

Wow, they feature adjustable accuracy. That's something I really miss even at high end test gear, to select between 0.5%, 2.5%, 10%, ... etc

[Aldo22]

Why do these devices only work from the μH range?

70% of my SMD inductors are in the nH range.

I can measure these with the NanoVNA, but it is a bit tedious.

Or am I interpreting this wrongly?

[Phil1977]

Just because 10cm of straight wire already have 0.1μH of inductivity.

To measure on this scale you need matched RF connections - so using a NanoVNA seems very legit, though not really comfortable.

The other reason is that only inductors over a certain "strength" behave ideal enough to be characterized buy a single μH-number. I´m no RF expert, but from my SMPS and denoising experience I think you need more than just the inductivity to characterize e.g. a ferrite bead that´s switched into the gate control of a power mosfet. You need the RF response including the Q-factors / absorption coefficients. But that´s out of the scope of a simple LCR-meter and it can again be solved by measuring with the VNA.

[watchmaker]

Here is a video "review":

[iet]

Watched the video. At 3 minutes, measuring a 1000 uF capacitor. Multimeter-785 uF, tweezers-551 uF. Too big a difference compared to the nominal value.

[indman]

iet, this 1000uF capacitor is faulty, this can be clearly seen by Rs=2.192 Ohm and D=0.7599.
For a working capacitor of such capacity, these parameters should be an order of magnitude smaller. Check out my photo below.
The ZT-703S multimeter showed a capacitance of 795 µF then 785 µF, which also shows that the capacitance is not in order. The fact that the multimeter showed a higher value is also understandable, since the principle of measuring capacitance in multimeters differs from the principle of measurement in bridge-type LCRs.

[iet]

It turns out that if you measure the capacity with a multimeter, the capacitor is slightly outside the 20% tolerance. If you measure with tweezers and without additional parameters, it is clear that the capacitor is faulty. Even taking into account the faulty capacitor and the different measurement principle, the difference of 234 uF is very large.

[indman]

Even taking into account the faulty capacitor and the different measurement principle, the difference of 234 uF is very large.

You are mistaken, on faulty capacitors of this type, the capacitance measured with a multimeter and a LCR bridge-type meter can differ by more than 1.5-2 times. If a faulty capacitor has a leak, the multimeter may, in some cases, show a capacitance that exceeds more big 20% tolerancethe rated capacitance. This fact is well known to experienced radio amateurs.

[tonyalbus]

Here my Hands-On video, it arrived this week.

Just like with the first types of the Scopemeter from Zoyi, its seems for now only available at AliExpress SNAKOL store.
that seems like their early release store. again no branding on the box, that on later models prob. will
ZT-MD1   https://go.tonyalbus.com/ZT-MD1

[indman]

tonyalbus,Thanks for the quite informative video!
This product still leaves many mysteries and questions. It is difficult, of course, to demand any high characteristics for such a low cost. Your video showed that the tweezers are quite fast in measurements and the RLC recognizes the main denominations with confidence.
But there are big doubts about the reliability of the secondary parameters Rs, D, Q. This difference is especially clearly visible in the test where you measure a capacitance of 4700 μF. The D parameter of the tweezers is shown as 1.5, but on your Rioshui 4090 it was determined to be 0.6? The difference is almost 3 times!!!
Have you checked the reliability of the tweezers readings at frequencies other than 1 kHz? And also with a different test signal level of 0.3V?

[tonyalbus]

@indman
4700 uF
MD1.    0.6V - 1KHz :  4100 uF / D:1.3627
MD1     0.6V - 100Hz: 4140 uF / D 0.1763
4090C    1V - 1KHz :  3755 uF / D 0.6181
4090C    1V -100Hz : 3943 uF / D 0.0923
On the 4090C changing the voltage did not matter, did not try on try on the MD1
The MD1 seems consistant with his (wrong?) value
I must add, i did not calibrate and used the 4090C for a while..

[indman]

tonyalbus, Thank you, but do you agree that such testimony raises questions? Could you measure a few more examples of high-capacity capacitors, for example 1500-3300 µF?

[tonyalbus]

@indman,
At this point, i am not that into D and Q values, so i am not sure what i it should read.
Myself i will not be using the product to much as i have the 4090C ready on the desk, and will be moving on the the next device in my queue
TheDevpom will be receiving one also, i understand, he usualy dives deeper into the details, especialy now reading your comments
so who knows maybe he will.
 

[indman]

Do I understand correctly that ZOYI sent you these tweezer for review?

[Phil1977]

Do you know the reference resistor these tweezers are using? Is it switchable at all?

As far as I know most serious LCR meters switch the resistor that´s in line with the internal AC source and that´s also used as the current shunt. For low resistance, high capacitance or low inductance you want low reference resistance and vice versa.

I could imagine these tweezers only use one value or a very limited set of values. Then it´s no surprise that large capacitors (and especially their ESR) can not precisely be measured.

Anyhow, these things seem much more versatile than the DMM-like tweezers.

[indman]

Anyhow, these things seem much more versatile than the DMM-like tweezers.

This is true, but if the secondary parameters Rs,D,Q cannot be trusted, then they become a useless addition and can mislead you, right?

[Phil1977]

Anyhow, these things seem much more versatile than the DMM-like tweezers.

This is true, but if the secondary parameters Rs,D,Q cannot be trusted, then they become a useless addition and can mislead you, right?

Hard to tell without trying this thing.

With conventional LCR-meters I always like to see the phase angle because it easily tells you how ideal a component is. A resistor with nearly zero degree, an inductor with 90°, a cap with -90° means you don't need to worry about anything parasitic.

This plausibility check alone would make the secondary display worth to watch. And if this plausibility check is not working, then I honestly would also not trust the main value.

[indman]

With conventional LCR-meters I always like to see the phase angle because it easily tells you how ideal a component is. A resistor with nearly zero degree, an inductor with 90°, a cap with -90° means you don't need to worry about anything parasitic.

D,Q also provide very useful and valuable information about the quality of the component.

[ZhuraYuk]

Seems to have identical specs to FNIRSI LCR-ST1. Similar design, just UI is different. I wonder if they share same board.
Would be great if tonyalbus did the teardown, that would be truly exclusive content.

[tonyalbus]

Seems to have identical specs to FNIRSI LCR-ST1. Similar design, just UI is different. I wonder if they share same board.
Would be great if tonyalbus did the teardown, that would be truly exclusive content.

FNIRSI sending me a LCR-ST1 too, its on its way, so can teardown both

[Feuerbard]

Seems to have identical specs to FNIRSI LCR-ST1. Similar design, just UI is different. I wonder if they share same board.
Would be great if tonyalbus did the teardown, that would be truly exclusive content.

board not the same but soc similar .

[indman]

Artery AT32F403ACGU7 - ARM Cortex-M4F. Freq. - 240MHz, FLASH-1024 Кb, SRAM - 96+128 Kb 
The price in China is approximately $2 per unit.

[TimMc]

FNIRSI sending me a LCR-ST1 too, its on its way, so can teardown both

Thank you for your demonstration and review! You inadvertently convinced me to get a DMMCheck Plus Rev 8.

Are they both using a 4-wire method for measuring resistance? Would this be necessary given the size of the tweezers?