Smart SMD tester MS8911.

[mawyatt]

Accurately measuring 1 mill-ohm is difficult indeed!! How good is the repeatability??

With a 10ma source current the DUT voltage is only 10uV, and why the Bench type LCR meters utilize much higher currents (some > 0.1a rms). Maybe a good zero ohm calibration can remove effects as the DUT current must be limited to something practical with a small battery powered handheld tweezer. Recall that some of low cost battery powered Milliohm meters source up to 0.2a DUT test current, but they also use a large 18650 battery. 

BTW the GS8632 isn't that impressive an op-amp with 3.5mV offset and 2.4uV/C drift, the INA826 isn't that outstanding either, however one must consider the product cost target!!

Anyway, curious as how well these tweezers perform with low milli-ohm impedances. Maybe they have some clever design tricks that make this repeatable and accurate, detailed testing against known good references should show the performance.

We are temped just to "see"

Best, 

[Frex]

Hello,

The FNIRSI LCR-ST1 seem effectively a great device, at least on the paper..
Many of us want to know how it really perform.

I initially would buy the Shannon ST42, but the fate decided not.
I was unable to buy it on Aliexpress despite many others orders before
and for very obscure reasons (many time spend and lost with their support).
Shannon itself had tried to help me, but without luck...(thanks to him anyway).

So, I finally ordered today the LCR-ST1 for about 30€.
It is less accurate than the ST42 but that would be fine for my usage (I hope).

I will gave my impressions and do some test as soon it will be in my hands
at the end of month.
Regards.

Frex

[iet]

BTW the GS8632 isn't that impressive an op-amp with 3.5mV offset and 2.4uV/C drift, the INA826 isn't that outstanding either, however one must consider the product cost target!!

I didn't write an impressive op-amp. Yes, zero drift is when less than 1 μV, it just happened somehow mechanically after looking at many datasheets. But still, it is not so easy to find a replacement for it, given all the characteristics and low price. It is necessary to consider everything together with other elements of the circuit.
Regarding repeatability. Naturally, it should be. But this must be tested by yourself.
On the Chinese forum there is a measurement with Fnirsi tweezers of inductance 0.47 uH-0.5 uH.
While the tweezers arrive, preparations are underway for in-circuit measurements. In-circuit measurement of the coil of inductance 0.8 uH.

[iet]

Hello,

The FNIRSI LCR-ST1 seem effectively a great device, at least on the paper..
Many of us want to know how it really perform.

Hello,
The first photos posted give hope.
The basic things are pretty good and you can see the good quality of the tweezers.
The tips of the tweezers. This is a very important detail that affects the reliability of the measurements as a whole. The tips should not be very thin and sharp, this is not very good in practice. They should be of a certain thickness and retain rigidity, and with notches this is generally excellent.
I specifically made a screenshot from a Chinese forum, may these guys forgive me.

[miniant]

It is interesting that on the official Fnirsi website you cannot find anything about the LCR ST1.
Is there a user manual somewhere? Where can the firmware be downloaded from and what is the loading procedure?

[iet]

It is interesting that on the official Fnirsi website you cannot find anything about the LCR ST1.

Let's wait until everything appears on the official website.
New videos.
https://www.bilibili.com/video/BV1eS42197aL/?spm_id_from=333.788.recommend_more_video.-1

[S2084]

I don't have expensive measuring devices... I passed a current of 1 ampere through a current shunt rated at 1 milliohm...and I measured the voltage drop on the current shunt ... Here's the result

[iet]

Here's the result

Repeated measurement showed a result of 900 uOhms. This is good.
 Another correct solution in the tweezers, which is necessary in practice - simultaneous display of three parameters C, D, ESR when measuring capacitors. In other tweezers they are separated C + D, C + ESR. That is, we save time on one switching, which is much more convenient. On the display we really have all the information about the capacitor at the same time, because cases are different.

[indman]

Repeated measurement showed a result of 900 uOhms. This is good.
 

What the hell are the units of microohms,milliohms on these tweezers if the manufacturer himself has indicated a starting range of 10 milliohms and even with a huge error? This is the same as trying to measure the same resistance on MASTECH 8911 tweezers.

P.S Тигра,завязывай с хуйней!

[S2084]

The stated capacitance of my scope is 15pF, 1Mohm

[iet]

These tweezers from FNIRSI work beautifully. Once again I was additionally convinced that it was not in vain that I ordered them.

[iet]

Preparation of in-circuit measurements continues. For this test, a solid polymer capacitor with a capacitance of 33 uF and a voltage of 50 V was selected. Manufacturer Nichicon, CV series. In the documentation, we find the maximum esr of 36 mOhms at a frequency of 100 kHz. The tweezers measure at a frequency of 10 kHz.
https://eu.mouser.com/catalog/specsheets/e-cv.pdf

[iet]

I continue to prepare for testing the FNIRSI tweezers.
There are some difficulties in measuring capacitors in the picoFarad range.
In the initial state, the tweezers should have zeros. When moving the probes in one direction or another, an error occurs. Therefore, measurements of such capacitors should be carried out at a fixed distance between the probes.
The second problem. SMD capacitors. They are small in size, which will introduce a certain error.
Therefore, it is best to use capacitors with leads soldered into the test board at a distance that corresponds to the distance between the tweezers probes.
If the tweezers are working correctly, the measured value of the capacitance of a 1 pF capacitor should be equal to twice the value when connected in parallel.
Measuring the capacitance of a 1 pF capacitor and in parallel 2x1 pF.

[S2084]

a short review of fnirsi lcr-st1 (in the context of my tasks)

https://youtu.be/rcQORKE9kPs

[iet]

Cool video of in-circuit measurements.
Measurements at this level are only possible with rigid probes. A very smart solution from FNIRSI.
The only remark. It is clear that it is convenient to shoot video in automatic mode at a frequency of 1 kHz. But it would be interesting to see the results of measuring the esr of solid capacitors at a frequency of 10 kHz.

[iet]

New firmware LCR-ST1-V1.4 has been released.
https://www.mediafire.com/file/qccivnk8wa31cyz/LCR-ST1-V1.4-20240803.bin/file

[iet]

Tweezers FNIRSI LCR-ST1. First impressions are very pleasant. Optimal dimensions, beautiful, durable body. Therefore, it fits comfortably in the hand.
I inspected the tips, calibrated the tweezers.
First, measurement in the picofarad range.