LCR Tweezer Fnirsi ST1 vs. Zoyi MD1

[mawyatt]

I apologize - I did not mean to be misleading! I actually earned my PhD 24 years ago, but in the humanities; I teach / serve as a Dean at Campbell University in central North Carolina. The university has a relatively new (~10 years old) School of Engineering, and I am finally getting a chance to fulfill a long-standing desire to sit in on a circuits class. Despite my professional focus on the humanities, I have been tinkering with designing / building circuits for 40+ years, and while I have generally succeeded in building something that works, I have always been painfully aware of how much I am "guessing" at design choices or at values to use (e.g., for a simple RC filter to quiet the bounce on a mechanical switch). Or as I often say, I have worked by trial and lots of error. Thus far, the class has been extremely enjoyable and has already filled in quite a few of the gaping holes in my knowledge. And this forum is adding to my knowledge as well!

That must be fun to sit in on an area you are interesting in learning about

Electronics is fascinating, has been for us for almost 7 decades

If you are interesting in better understanding of things try approaching from a fundamentals standpoint. Learn the basics in detail, then proceed with the application of such.

It lots of fun to sketch out a simple circuit on the back of an envelope, write a few equations, note some bias voltages/currents and waveforms. Then build on a protoboard and have it work 1st time without resorting to Google or LTspice, just pen, paper and trusty old HP calculator

It's also fun being around young minds, you can spot the potential stars. When an Adjunct creating and teaching 1st advanced graduate classes in RFIC design we spotted those students and hired them (inside advantage) 

Best

[awakephd]

That must be fun to sit in on an area you are interesting in learning about

It has been very fun! With the professor's permission, I have been doing all of the work - homework, labs, quizzes, exams - it has been a great reminder to be on the student side of things. As dean, I oversee a graduate/professional program, and nearly all of our students are working significant hours, many with full-time jobs, families, and life responsibilities. I am planning to recommend to my faculty that they look for a class that they would sit in on, just to remember what it is like to be a student while juggling a full-time job.

If you are interesting in better understanding of things try approaching from a fundamentals standpoint. Learn the basics in detail, then proceed with the application of such.

Indeed! The course I am taking has proven to be "just right" in terms of what I already knew vs. what I need to learn. I have long been conversant with things such as Ohm's Law and the principles of how BJT and MOSFETs work. The class I am taking is more or less a "part two" class on circuits - the first class having introduced students to the things I have painfully learned (mostly) over many years. I was a bit concerned that my math skills would be too rusty; once upon a time I loved maths up through Calculus, but it has been many, many years since I have worked out a significant integral or derivative. So far, however, I am finding that what I have needed mathematically has come back quickly, and it has renewed my enjoyment of math. One thing that has been particularly interesting to observe is that often I know the practical implications / applications that the students know only in theory (and I may only now be learning the theory). For example, I've blown up more than my fair share of MOSFETs along the way, so when we discussed h-bridges and the problem of shoot-through, I could have testified!

[DaneLaw]

In regards to the zero/relative-feature on Fnirsi ST1.
On lower values fx 10mOhm from traces' it seems to relative that value on top, every time you hit it, a power cycle will remove that offset.
Lookslike its adding the value.?
https://i.imgur.com/i7YdCIs.mp4

While on bigger values fx 100mOhm it does seem to null it.
Tried to zero it on 100mOhm res (before the video starts), and the corresponding reading does cycles down around 0mΩ
https://i.imgur.com/X6kHfFM.mp4

[elantric]

New one

https://www.banggood.com/ru/LCR-1S-Smart-Tweezers-LCR-Tester-100kHz-CNC-Metal-Case-High-Accuracy-Portable-1_47-inch-Color-Display-Intelligent-Auto-Range-Function-p-2022417.html?akmClientCountry=MD&cur_warehouse=CN&ID=6329370&rmmds=search (Attachment Link)

QPLink LCR TWEEZERS
https://www.eevblog.com/forum/testgear/qplink-lcr-1s-smart-tweezer-(100hz-120hz-1khz-10khz-100khz)-50$/

[tigrr]

QPLink LCR TWEEZERS

QPLCR User Manual - PDF, 1.58 Mb https://mega.nz/file/I5UABC6C#jVBlZjjKRdjQ-qyR2wumsVWKOKlYn0bU0DAoV51bvQk

[Paul T]

I now have both devices.  This past week I received a FNIRSI LCR-ST1 (v1.5 F/W).

I definitely like the ZOYI ZT-MD1 (v1.8 F/W) better. 

Here's 10 reasons why.

(1) The FNIRSI wheel operation (pushing) has a flaky response, like a worn-out switch.  Almost have to use my fingernail to push it.  Maybe it should be set higher.
(2) The refresh rate is similar, but the ZOYI settles in to a stable value a little better, especially on resistance.
(3) Resistance < 0.5 ohms is way more accurate on ZOYI.  Seems that the ZOYI is closer to a true 4-wire setup.  The ST1's REL feature is not very helpful.
(4) Inductance < 50uH is consistently low on the FNIRSI.  Same 10kHz frequency.  Can't REL it out.
(5) Schottky diodes measure 0.50 on the FNIRSI, could be confused for a silicon diode.
(6) The FNIRSI tips are more easily misaligned when squeezing.
(7) Bigger lithium cell on ZOYI.  Battery life is fine, but why is it half?
(8 ) The FNIRSI charges at 340 mA, which is C = 1.36, battery life might be affected?
(9) The price is about 25% more from FNIRSI.
(10) The ZOYI is easier to read the screen due to font and size, less busy.

On the other hand, the FNIRSI LCR-ST1 has some things going for it:
(1) More comprehensive data logs.
(2) The gold plating on the tips was more durable for me (doesn't flake off at the tip).
(3) The FNIRSI and the carry case look a little nicer and more colorful. 
(4) The screen protector is very clear and undamaged.  You can rip off the pull tab and leave it on.  The ZOYI screen protector is like thin food wrap.
(5) Only the ST1 has internal blade serrations, preventing radial lead components from rotating 90 degrees when squeezing onto the outside.

As a result, both sitting in front of me, I would definitely reach for the more accurate and easier-to-navigate ZOYI ZT-MD1 for most tests. 

Maybe I would be more likely to show off the FNIRSI to a friend.  That's about it.

[Propretor]

Even with firmware 1.6 in diode test mode, the reading on the screen must be divided by 1.41 to find out the true value of the diode voltage!

[Paul T]

Even with firmware 1.6 in diode test mode, the reading on the screen must be divided by 1.41 to find out the true value of the diode voltage!

Please provide a real case that leads you to this conclusion 

[Propretor]

Please provide a real case that leads you to this conclusion 

You can take any diode or Schottky diode, determine the voltage drop with a quality DC instrument, and then make similar measurements with the FNIRSI LCR-ST1. Divide the value that the FNIRSI LCR-ST1 shows by 1.41 and you get a value that is very close to the real value measured by a normal instrument. The explanation for this effect is very simple - the FNIRSI LCR-ST1 has no DC operation mode, and the developers forgot to divide the reading by 1.41 (SQR2). The actual, effective or RMS value of a harmonic signal is 1.41 (SQR2) times smaller than its amplitude. It's simple
The difference will only be due to the accuracy of the measurement and the different amount of current flowing.

[Paul T]

Please provide a real case that leads you to this conclusion 

You can take any diode or Schottky diode, determine the voltage drop with a quality DC instrument, and then make similar measurements with the FNIRSI LCR-ST1. Divide the value that the FNIRSI LCR-ST1 shows by 1.41 and you get a value that is very close to the real value measured by a normal instrument. The explanation for this effect is very simple - the FNIRSI LCR-ST1 has no DC operation mode, and the developers forgot to divide the reading by 1.41 (SQR2). The actual, effective or RMS value of a harmonic signal is 1.41 (SQR2) times smaller than its amplitude. It's simple
The difference will only be due to the accuracy of the measurement and the different amount of current flowing.

Thank your for the theory on this.  Since I have not encountered this error, could you show a real case?  Personally I have noticed the diode function lacks accuracy, but all the readings were lower not higher.

[jackobo]

Lads, in the end of the day, which one to get to have some play Fnirsi or Zoyi? )) the price nowadays +- virtually the same.

[Paul T]

I still feel the same as my detailed post several posts above.

[DaneLaw]

I also lean on MD1 it's a tad more stable but the tips is also not as pointy as ST1.

Some things that ST1 got that the MD1 doesn't are selective secondary parameters.
On the ST1, you can push in the toggle switch with a long push, and jump between the secondary values on a given reading, Q, Z, X, D (from +20s https://tinyurl.com/mty2ye5k )
The back is also magnetic on the ST1.. Easy to hang on anything metal (there is a small metal sticker-sheet incl. to hang it at any given place of choice).

Got 3 of these budget LCR Kelvin AC tweezers.
*QP-LINK 1S, *Zoyi MD1 and *Fnirsi ST1 "side by side" to give an idea of the size.

QP 1S is quite a bit more expensive, and it shows in the alu build & design. It's more than double, at $48 delivered (incl. 25% EUVAT/DK), but it also got more features... like a 0.1 V test mode, which can be quite useful for keeping semiconductor junctions off, avoiding latch-up, or damaging fragile ICs, while also reducing core saturation in small inductors and preventing inaccurate or false readings in nonlinear or sensitive components, like ceramic capacitors or high-impedance parts.

It’s also worth noting that the QP LCR 1S has a 100 kHz measurement mode that, alongside 0.1V, can help highlight parasitic effects & frequency-dependent characteristics, which could be useful in real-world high-speed or analog designs.. QP-1S also got a 120 Hz mode, which neither MD1 nor ST1 has.
That can be handy for checking parts used in full-wave rectified 60 Hz power supplies, like electrolytic capacitors and other power components, since it reflects real-world conditions like AC ripple & line frequency, it can help you get more accurate readings of capacitance and ESR..Especially in power, audio, and low-frequency magnetic circuits.

QP-LCR LINK1S will also will do/measure DC voltage which I personally find handy to have in a small LCR tweezer, up to around a max of 16V* (if I recall correctly*) and it support higher tolerances like 10.000 count across the full range and it got an accelerometer that will flip the display according to your orientation, or you can user-select in the menu, but it could be that QP LCR 1S is out of production here in 2025, as very few listings last time I checked and prices were significant higher, so perhaps down to "old stock".

Zoyi MD1 got the biggest gap of the three tweezers (highlighted below)

[jackobo]

dont need them two Fnirsi and Zoyi MD1 or even 3 including QP. Just ordered ZT-DQ02. In addition to it having a hard choice between Fnirsi and MD1 tweezers, to play with. Should I better flip the coin?

[DaneLaw]

dont need them two Fnirsi and Zoyi MD1 or even 3 including QP. Just ordered ZT-DQ02. In addition to it having a hard choice between Fnirsi and MD1 tweezers, to play with. Should I better flip the coin?

A tad conflicting, as in if you don't need an LCR tweezer, then don't get it.
Wait for your Zoyi DQ02 and be familiar with that, and see if it will saturate your needs.