Smart SMD tester MS8911.

[iet]

I bought smart SMD tester MS8911.
Nowadays there is a lot of work with small components on boards.
Positive impressions.
Easy control of functions.
A good set of basic and additional parameters.
Acceptable accuracy and resolution.
Does not require calibration.
High stability of display readings.
Versatile, durable probes.
Negative impressions.
Small distance between probes.
No backlight.
Adapted for in-circuit measurements. Measuring voltage 0.1 and 0.5 V.
Three frequencies 0,1,1,10 kHz.
Question for those who use similar testers: Is there a need for a lower measuring voltage for in-circuit measurements?

[Martin72]

Hi,

Is there a need for a lower measuring voltage for in-circuit measurements?

In in-circuit measurements, the low voltage is used to prevent other components from being addressed, i.e. to make them conductive that could falsify the measurement.
Sometimes this works, but usually not.

[iet]

The question arose when I saw a small Esr70 measuring device. It has a measuring voltage of 0.04 V.
https://www.peakelec.co.uk/downloads/esr70-datasheet-en.pdf
One more question for tweezer users. In Esr measurement mode, there is a Q symbol on the display. What does it mean and how to interpret it?

[iet]

Hi,

Is there a need for a lower measuring voltage for in-circuit measurements?

In in-circuit measurements, the low voltage is used to prevent other components from being addressed, i.e. to make them conductive that could falsify the measurement.
Sometimes this works, but usually not.

Hi,
Yes. After some in-circuit measurements, the influence of the measuring voltage on the value of the capacitance and Esr of the tantalum capacitor was recorded. There was a diode in its circuit. Depending on the measuring voltage of 0.1 V or 0.5 V, a small difference in the value of the capacitance and a significant difference were noticeable in the meaning of Esr.

[iet]

Unfortunately, I did not receive a response from the users of this tweezers regarding the secondary parameter Q on the display when measuring Esr of capacitors.
Now it is clear that the display shows additional information about the losses in capacitor-Q.
Q represents the efficiency of the capacitor and represents the ratio of energy stored in the capacitor to the energy dissipated as thermal losses due to the equivalent series resistance (ESR). Q is directly related to ESR because lower ESR means higher Q since it’s inversely proportional.
Two capacitors with the same capacitance and voltage values.
They have the same Esr, but the Q quality value is different.

[iet]

After half a year of using the tweezers, there are no complaints about the work. Everything is according to the specifications. The only inconvenience is that with intensive use, the battery is discharged. One of the solutions to this problem is here. Anyone interested can try it.
https://www.hkepc.com/forum/viewthread.php?fid=146&tid=2724545&extra=page%3D1
It’s especially cool to see how it quite easily copes with resistance like 10 mOhms, that is, at the limit of its capabilities without preliminary calibration.

[iet]

This also applies to the measurement of small SMD inductances.

[Martin72]

As a rule, you cannot trust the last digit of a digital display.

[indman]

It’s especially cool to see how it quite easily copes with resistance like 10 mOhms, that is, at the limit of its capabilities without preliminary calibration.

Since the tweezers do not have a full 4-wire measurement circuit, the readings of your instrument when measuring small resistances will depend on the force of pressing on the pins of the part. Besides, as Martin72 correctly noted, the last digit in this device is displayed with an uncertainty which is specified in the manual.

[iet]

As a rule, you cannot trust the last digit of a digital display.

Well, if the last number is constantly dancing, then yes. But if it is absolutely motionless, then I think it’s possible.
Today a 10 mOhm resistor and 1% accuracy arrived, so I repeated the measurement using the pressing force of the tweezer plates themselves.

[Martin72]

Well, if the last number is constantly dancing, then yes. But if it is absolutely motionless, then I think it’s possible.

You know what "digits" means ?

[iet]

Looks like a very good tweezers. I will make an order for comparison with my MS8911.
Fnirsi used all modern technologies. Beautiful color display, case, battery.
Parameters are also without unnecessary fantasies -1 pF, 1 uH, 10 mOhms.
I liked the tips with notches. A very correct solution for holding smd components.

[iet]

In general, 10 mOhms by modern standards is an insufficient limit. The manufacturer deliberately stops at a minimum of 10 mOhms, thus cutting off everything that is measured below. It's a bit sad, but what can you do?

[AVGresponding]

In general, 10 mOhms by modern standards is an insufficient limit. The manufacturer deliberately stops at a minimum of 10 mOhms, thus cutting off everything that is measured below. It's a bit sad, but what can you do?

Resistances this low are difficult to measure accurately with 2-wire systems, and low current

[iet]

Well, if it correctly measured a 10 mOhms 1% resistor, then I have no complaints about the tweezers. It is clear that I would like a few more digits after the decimal point, but this is a different class of devices. What do we need tweezers for? This is a quick check of components on the board. This is the identification of components without marking. This is a search for faulty components, mainly various types of capacitors. It copes with these things perfectly.
Here is a low-impedance capacitor that has been repeatedly tested by various devices, according to the documentation, the maximum esr is 12 mOhms.
The basic accuracy of 0.1% for tweezers is a very nice thing. But most electronic components do not fit even into the accuracy of 1%, with rare exceptions. Therefore, the basic accuracy of 0.5-1% is fully justified. This is also related to the price. The higher the measurement frequency and accuracy, the more expensive the device.

[iet]

I checked the tweezers on capacitors. I measured the capacitance of two capacitors.
2210 nF 1% and 2.2 pF. The 2.2 pF capacitor is soldered to the board with leads, the distance between which exactly corresponds to the distance between the tweezers tips, to minimize measurement errors.

[iet]

I have already measured the minimum inductance, but here is the measurement of the large inductance of the transformer.

[iet]

The new tweezer from Fnirsi LCR-ST1 are being actively discussed on a Chinese forum. Some criticize, others praise. They post photos of comparative tests.
http://www.crystalradio.cn/thread-2149620-1-1.html

[Martin72]

Some criticize, others praise.

Forums are the same all over the world.

[S2084]

I have only positive impressions! and there really is a four-wire measurement circuit...

[iet]

I have only positive impressions! and there really is a four-wire measurement circuit...

Hi
Super interesting information regarding the four-wire measurement circuit. The display shows 900 uOhms. Wow. A huge surprise. And what is the minimum resistance it can measure? This is all very intriguing.
250 mA battery. How long does the battery last for continuous operation of the tweezers?
And more questions. Have you measured the minimum capacitance and inductance? What can it really do? Are there any problems when working in automatic mode? Because there is quite contradictory information from the Chinese forum.
Thanks.

[S2084]

Hi! If you are interested in any specific measurements, visit my telegram group.... I very rarely visit this forum.

[Martin72]

I very rarely visit this forum.

Time to change that.
If you want to know more, visit me somewhere other than here, I don't think it's that great in terms of forum content.

[S2084]

I very rarely visit this forum.

Time to change that.
If you want to know more, visit me somewhere other than here, I don't think it's that great in terms of forum content.

With your permission, I will reserve the right to decide on this matter for myself.

[iet]

Hi! If you are interested in any specific measurements,

Hi
Basically, you gave me the information that I was missing. And measuring a 1 mOhms resistor is very cool.Thanks.
Your photos show part of the board with some operational amplifiers like GS8632, INA826. GS8632 is a precision operational amplifier with virtually zero drift and low power supply, which has a positive effect on measurements in the very low-resistance range, which we see when measuring a 1 mOhms resistor. INA826 is a cost-effective instrumentation amplifier that offers extremely low power consumption. Everything is well thought out.

[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.

[iet]

Is there a user manual somewhere?

The manual appeared on the FNIRSI website.
https://www.fnirsi.com/pages/download_manuals?srsltid=AfmBOorKBDr-mx29KBeJvINbB8NMEgN6rGgbdDJ7lP5H4GzJL9g6_q-w

[miniant]

Thank you
I ordered a piece and I'm waiting for it to be delivered.

[iet]

I spent a little time studying the measurement in the picofarad range. Everything is very simple. We set 0.0 pF on the display by pressing the Power on/off button. High stability of zero readings, no drift for 3 hours. Measurement in this range is carried out in the normal mode. The only condition is that the distance between the tips must be maintained during measurement.

[miniant]

It's very good, but how does it behave when measuring inductances of a few tens of nH or smaller ?

[iet]

It's very good, but how does it behave when measuring inductances of a few tens of nH or smaller ?

Behaves perfectly on nH.

[iet]

This smd inductance has already been measured by MS8911.

[iet]

The series connection of two 1pF capacitors has already been measured by the MS8911.

[iet]

And now a little about something else. Let's look at the maximum values ​​of two measured parameters - L, C. A very interesting thing turns out.
Maximum inductance. The ST1 tweezers have 10 H.
I measured the primary winding of the transformer.
The MS8911 tweezers have 60 H.
Repeated the measurement of the large inductance of the transformer, made by the MS8911.
The inductance results for the two tweezers almost coincide.

[iet]

Maximum capacitance value that tweezers can measure is 22 mF.
Measurement with a multimeter with a limit value of 100 mF.
33 mF.
55 mF.

[iet]

Inductance 0.1 uH was measured with two tweezers with the same result.
Now let's check the secondary parameter Rs when measuring inductance with tweezers LCR ST1. More accurate tweezers LCR Pro1 Plus.

[iet]

Resistors.
Minimum value - 0.1 mOhms.
First, it is necessary to perform a good zeroing of the readings with the tweezers probes closed. The upper part of the button from the old equipment was chosen as a device. The tips fit very tightly inside and provide a very reliable high-quality contact.
In this position, the tweezers were tested for 1 hour to understand what kind of drift it had. Within half an hour, the drift was 0.2 mOhms. At the end of the tests, it increased to 0.3 mOhms.
After a short break due to battery charging, I continued to study the drift of the tweezers in the milliohm range.
In the closed probe mode, the tweezers worked for 4 hours until the battery was completely discharged. Working for 3 hours with a green glow of the battery charge indicator, the drift did not change.And the most interesting thing is that with a red glow of the battery charge indicator, this drift remained at the same level until the battery was completely discharged.
In addition to studying the drift of the tweezers, my device for the zeroing mode of readings has proven its high reliability.
Resistor 1%.

[iet]

I have good news. My tweezers have new tips. The problem with good tips has always been. They are all of different design, have their own coating of different metals. But whatever the design features, they must be thin enough at the tips. The area of ​​contact with the component is very small, so over time the coating wears off. This leads to deterioration of contact and introduces some error in measurement. This is most noticeable in the mOhms and pF range. My tips are made of polished brass plates 1 mm thick. Excellent contact and rigidity. Easy to process. The contact area has increased slightly. Durable, wear-resistant. Always maintain high quality contact.
I conducted an experiment on the drift of tweezers with short-circuited probes. I repeated the experiment on a 5 mOhms 1% resistor. The clamping force was fixed. Over the course of 1 hour, the drift was +/- 0.2 mOhms.

[MiniCheck]

I have good news. My tweezers have new tips.

Where did you get these tips from?

[iet]

Where did you get these tips from?

I made them myself. I had to work a little with different tools.

[iet]

On the FNIRSI website firmware V1.5.
https://www.fnirsi.com/pages/download-firmware

[iet]

Resistors 1,1.5,2 mOhms 1%.

[iet]

In the FNIRSI LCR-ST1 thread on the Chinese forum there is very interesting information about the changes that were made to different firmware versions V2,3,4,5.
LCR-ST1-V1.5-20240827
1. Repair the logic of automatic shutdown setting
2. Add the function of identifying the direction of diode

LCR-ST1-V1.4-20240803
1. Repair the abnormal progress of resistance measurement in some intervals

LCR-ST1-V1.3-20240725
1. Repair some problems of diodes

LCR-ST1-V1.2-20240714
1. Add the function of measuring on and off under diode
2. Add Z and X secondary parameters
3. Add data saving
http://www.crystalradio.cn/thread-2149620-4-2.html

[iet]

After measuring the resistors, I measured the esr of a polymer capacitor from Panasonic SP-Cap, GY 820 uF, 2v. ESR<3 mOhms.
https://api.pim.na.industrial.panasonic.com/file_stream/main/fileversion/8713

[iet]

I made another pair of tips from polished brass. The thickness is the same as the original probes - 1.5 mm. They fully correspond to the dimensions and profile of the original probes. In addition, bolts were used to attach the tips. This completely eliminated the slightest displacement of the tips. They are practically eternal, there is nothing to wear out there.

[DaneLaw]

I made another pair of tips from polished brass. The thickness is the same as the original probes - 1.5 mm. They fully correspond to the dimensions and profile of the original probes. In addition, bolts were used to attach the tips. This completely eliminated the slightest displacement of the tips. They are practically eternal, there is nothing to wear out there.

What's your take on the curved tweezers.?
One of the benefits of the Fnirsi variant ST1 is that it also comes with curved/hooked tweezers.

The Zoyi MD1 also comes with an extra spare set for an added cost of +0.15cent, but it looks identical to the main.

[iet]

What's your take on the curved tweezers.?

It's great that FNIRSI gives them away. Sometimes it's necessary. Although the main work is straight tips.
I must say that the original tips will be used in the same way as the brass ones. They have notches and this has its practical application. It turns out that I will be working with three pairs of tips.

[DaneLaw]

What's your take on the curved tweezers.?

It's great that FNIRSI gives them away. Sometimes it's necessary. Although the main work is straight tips.
I must say that the original tips will be used in the same way as the brass ones. They have notches and this has its practical application. It turns out that I will be working with three pairs of tips.

They aint free as per se, but an incl. addon on the ST1bundle that comes with the ST1-form-fitted casing.
Its around 2 to 3€ difference for the added angle tweezertips & bag.
You went for the bag-bundle or just the tool.?

Nowadays, it only looks like its the bag-bundle that is on offer, though 3 weeks back when I purchased one, you could select-
Only the Zoyi MD1 has arrived, which has impressed me sofar (with the price in mind)

[MiniCheck]

With this capacitor, RNS1C470MDS1 (47 uF, 16V), I get the following approximate readings with the Fnirsi LCR-ST1:

@100 Hz, 580 mOhms, 51 uF
@1 KHz, 73 mOhms, 50 uF
@10 KHz, 17 mOhms, 52 uF (the ESR reading does jump a bit)

The datasheet shows the ESR as 42 mOhms.

Here's the interesting thing: the Fnirsi LCR-P1 shows a sold 50 mOhms for the ESR and 55 uF for the capacitance.

The capacitor is brand new and both measuring devices have the latest firmware.

[4thDoctorWhoFan]

The datasheet shows the ESR as 42 mOhms.

At what frequency?

Here's the interesting thing: the Finirsi LCR-P1 shows a sold 50 mOhms for the ESR and 55 uF for the capacitance.

Again, at what frequency?

The ESR will vary considerably depending on the frequency.

[MiniCheck]

The 42 mOhms is at 100 KHz, 20 degrees C.

I don't know what frequency the Fnirsi LCR-P1 uses.

The data sheet is here for the capacitor: https://www.nichicon.co.jp/english/series_items/catalog_pdf/e-rns.pdf

[indman]

The capacitor is brand new and both measuring devices have the latest firmware.

It's hard to call these toys measuring devices.  Do you have more serious instruments to evaluate the quality of the capacitor
RNS1C470MDS1?

[Paul T]

The Zoyi MD1 also comes with an extra spare set for an added cost of +0.15cent, but it looks identical to the main.

I can confirm this.  Wishing for a serrated set which can hold onto loose piece SMD's.

[MiniCheck]

It's hard to call these toys measuring devices.  Do you have more serious instruments to evaluate the quality of the capacitor
RNS1C470MDS1?

  

No, I'm afraid not. I think they're ok for my needs.

[iet]

You went for the bag-bundle or just the tool.?

I ordered bag-bundle.
In-circuit measurement of resistors with new brass probes.

[iet]

This is what I wrote about. The gold coating of the tips has worn off after 9 months of intensive use in the areas of greatest contact.

[iet]

Measuring 0.1% resistors.ST1.
100R 0.1%     R:100.0             
100k 0.1%     R:100.0   
1M 0.1%        R:1.00   
On the Chinese forum, which has already been linked, there is a topic about a simple LCR meter. The design of a conventional meter gradually acquired the shape of tweezers. In my opinion, this is the first attempt to simultaneously display the maximum number of parameters of the measured component on the display. 6 parameters, plus frequency and range. The accuracy was quite good, especially surprised by the large-sized probes, even more rigid than my tweezers. The developer's idea is clear - to convert a desktop LCR meter into the shape of tweezers. A very interesting and promising thing, which can be considered a new qualitative stage in the design of LCR tweezers.
http://www.crystalradio.cn/thread-2150171-11-1.html

[iet]

I made a more advanced device for zeroing. At the same time, it can be used as a stand for tweezers.

[iet]

I measured the maximum resistance that I had -50 MOhm. Although in the technical specifications it is 10 MOhm. The value is displayed by the secondary parameter Rs. By the way, the Chinese tweezers in the photo have 100 MOhm.

[MiniCheck]

I made a more advanced device for zeroing. At the same time, it can be used as a stand for tweezers.

Is that something you have to do before using them?

[iet]

Is that something you have to do before using them?

Short Circuit Zeroing: First, select the test frequency that you want to zero. Insert a short-circuit piece into the test socket,
whether using SMD test tweezers or clamps. Short-press to enter zeroing mode. The instrument will automatically
measure and execute the corresponding short circuit zeroing after identification.
This is written in the manual. You decide for yourself whether to do zeroing or not. For example, you shorted the probes 1-3 times and you have N milliohms on the display. You decide whether this error will affect the measurement results or not. If not, then there is no need to zero. If you measure low-resistance resistances and picofarads, then you must zero. In addition, I have the corresponding components soldered onto the test boards and I immediately check the zeroing result.

[iet]

To finally solve the problem of the tips, I made another pair from copper plates 1 mm thick. Everything works fine.

[iet]

Measured 8 resistors connected in series, 10 MOhm. There is nothing to check the result with. MS8911 and a multimeter - 60 MOhm.

[iet]

After carrying out all the necessary things in the milliohms range, I measured the resistance of two 1 mOhms resistors connected in parallel.

[indman]

After carrying out all the necessary things in the milliohms range, I measured the resistance of two 1 mOhms resistors connected in parallel.

[4thDoctorWhoFan]

After carrying out all the necessary things in the milliohms range, I measured the resistance of two 1 mOhms resistors connected in parallel.

Perhaps I am missing something but why do you keep posting about the Fnirsi LCR-ST1 when this thread is titled about the MS8911?
I mean, there is a dedicated Fnirst LCR-ST1 thread.

[mawyatt]

Also, how much current do these tweezers utilize thru the DUT for low Z measurements?

Best,

[iet]

Also, how much current do these tweezers utilize thru the DUT for low Z measurements?

Best,

A very interesting thing. And the most interesting thing is that this information is not available for any tweezers.
https://upload.sunsky-online.com/res/guide/TBD06051996Manual.pdf
https://mastech-group.com/resources/QSG+%E8%AA%AA%E6%98%8E%E6%9B%B8/GLO_%E8%AA%AA%E6%98%8E%E6%9B%B8/GLO%E8%AA%AA%E6%98%8E%E6%9B%B8_%20%20MS8911.pdf
https://www.lcrresearch.com/_files/ugd/97c2bb_73362b7481694861a96b1bed0670c66b.pdf

[mawyatt]

This can be measured relatively easy with a small DUT resistor, say 1 Ω. Attach a DSO across the DUT and observe the measurement waveform from the tweezer, or if a DSO isn't available use a DMM. Keep the frequency low for the DMM since they usually don't respond well at higher frequencies.

Another option if one has a DSO with 50 Ω input impedance, is use the DSO 50 Ω input Z as the DUT and simply measure such with tweezers.

Maybe some folks with these tweezers can perform this simple test and report th results, we would IF we had any tweezers, unfortunately we don't!!

Best,

[iet]

This can be measured relatively easy with a small DUT resistor, say 1 Ω.

There are different ways to check.
I got the result that interested me. To do this, I had to put my hands on it and work a little. These capabilities are embedded in these tweezers, you just have to try to implement them. Such measurements are not an end in themselves, but a way to check real parameters.
A lot of talk about the diode function.
Actually, we must not forget that the tweezers are a bridge LCR meter. The D function is additional. But it is not made like in multimeters. That is, it is not finished. FNIRSI should either finish it or remove it altogether. And instead of a diode, make a measurement of the DCR resistance. This is done in the MS8911.
And if possible, then do it like in the LCR Pro1 Plus.
In a short period of time, an analysis of the serviceability of the semiconductor junctions of the diodes and transistors is carried out for breakage, partial or complete breakdown.
After the analysis, we see the result on the display.

[iet]

In this case, ST1 indicates low resistance, which corresponds to the short state.
For the correct interpretation of the short state, it is desirable that the tweezers could indicate 10 mOhms, or even better 1 mOhms. Then it will fully display the real situation.
Here is good information.
https://www.fluke.com/en/learn/blog/digital-multimeters/how-to-test-diodes#:~:text=A%20bad%20(opened)%20diode%20does,0.4%20V)%20in%20both%20directions.

[iet]

Faulty transistor.

[iet]

In-circuit measurement of diodes.

[iet]

There was such an opportunity and I bought a used Atlas DCA55. I checked the diodes on the board again, which were checked with two tweezers.

[iet]

Diode bridge. Faulty diodes of the diode bridge.

[iet]

Some conclusions can be made. Faulty diodes and transistors can be identified with ST1 tweezers. Both those soldered from the board and those in-circuit. I would like to have the ability to measure lower resistance in this mode, as is done in Pro1 Plus in Continuity mode. The continuity measurement can be used to test fuses, connectors, switches and other components.
I measured the resistance of 0.5 mOhm again with LCR Pro1 Plus tweezers.

[iet]

New firmware V1.6.
LCR-ST1-V1.6-20241121
1.Fix the problem of invalid reset

LCR-ST1-V1.5-20240827
1. Repair the logic of automatic shutdown setting
2. Add the function of identifying the direction of diode

LCR-ST1-V1.4-20240803
1. Repair the abnormal progress of resistance measurement in some intervals

LCR-ST1-V1.3-20240725
1. Repair some problems of diodes

LCR-ST1-V1.2-20240714
1. Add the function of measuring on and off under diode
2. Add Z and X secondary parameters
3. Add data saving
https://www.fnirsi.com/pages/support-and-downloads

[iet]

Video about ST1 tweezers with new firmware V1.6 and charts comparing measurements with other devices.

[iet]

There were many discussions on the forum about problems with calibration and stability of measurements in the milliohm range of the Fnirsi ST1. It seems that this was solved in the ANENG GN702 tweezers. They entered it into the calibration menu and this can be seen in the video when measuring a 2.3 mOhms resistor. It is clearly visible that the numbers do not move for several seconds, while the resistor value is accurately measured. There is also an option to rotate the screen in the menu. If this is so, then a certain progress in measurements in this range has been achieved. Can anyone confirm or deny this?
https://www.ebay.com/itm/286214675405

[DaneLaw]

There were many discussions on the forum about problems with calibration and stability of measurements in the milliohm range of the Fnirsi ST1. It seems that this was solved in the ANENG GN702 tweezers. They entered it into the calibration menu and this can be seen in the video when measuring a 2.3 mOhms resistor. It is clearly visible that the numbers do not move for several seconds, while the resistor value is accurately measured. There is also an option to rotate the screen in the menu. If this is so, then a certain progress in measurements in this range has been achieved. Can anyone confirm or deny this?
https://www.ebay.com/itm/286214675405

Confirm what?
I doubt it went over your head (as we even talked about it #61/#63/#65) that there is another cheap LCR tweezer, and there are differences between them, even though the specs are very similar.
https://www.eevblog.com/forum/testgear/lcr-tweezer-fnirsi-st-1-versus-zoyi-md-1/msg5646681/#msg5646681

To sum up, ZOYI is usually the OEM (original equipment manufacturer) behind most of the products sold under the Aneng brand.
Essentially, ZOYI design & manufactures the products, and Aneng later gets the clearance to rebrand & label ZOYI-products under the Aneng-name for certain markets.
Very common practice in China that things get rebranded for other markets.

[iet]

Confirm what?

My question was addressed to those who already have ANENG GN702 tweezers and they can confirm what is shown in the video - stability in the milliohm range. The video shows a measurement of a 2.3 mOhms resistor.
Regarding rebranding. Thanks for the information.
Unfortunately, I missed some things. Now I have carefully reviewed your message. I have a question for you. Do ZOYI MD1 and ANENG GN702 have the same menu or are there differences?

[DaneLaw]

Confirm what?

My question was addressed to those who already have ANENG GN702 tweezers and they can confirm what is shown in the video - stability in the milliohm range. The video shows a measurement of a 2.3 mOhms resistor.
Regarding rebranding. Thanks for the information.
Unfortunately, I missed some things. Now I have carefully reviewed your message. I have a question for you. Do ZOYI MD1 and ANENG GN702 have the same menu or are there differences?

Its usually the exact same product, as it tends to be when Aneng rebadges Zoyi (Zotek) products.  https://zotektools.com/products/
Their specsheet is also close to identical, just with a tad worse tolerances on the GN702 than what ZOYI put on their MD-1.

[DaneLaw]

I haven't updated my Zoyi  MD-1 for a while and I'm certainly not on the latest, which seems to be fw 1.8 or maybe 1.9?
Just checked.. my unit is on FW1.7 so an older fw but even there, and when you are in the menu (calibrate) where you can see your resistance value... it seems to be pretty stable way down in the low single digits mΩ by just shorting the tips with some force.

Another indication that it's the same product, is the firmware.. the Aneng GN702 in the video shows firmware 1.8, and that is also the firmware posted on the Zoyi -MD-1 int-download page.

Seems pretty stable down in the decimal (0.x) mΩ values.
An example by shorting the tips. (old fw 1.7)

[iet]

Its usually the exact same product, as it tends to be when Aneng rebadges Zoyi (Zotek) products.  https://zotektools.com/products/
Their specsheet is also close to identical, just with a tad worse tolerances on the GN702 than what ZOYI put on their MD-1.

All tweezers that have recently entered the market have very similar specifications and everything is more or less clear. Here I am more interested in some things about calibration in R, C mode.
 Your tweezers at the stability point show 0.4 mOhms for about 10 sec. This is good. Is it possible to get a value of 0.0 mOhms? If so, how many seconds does this value last?

[DaneLaw]

There are mainly 3 new models.. atleast i the budget category.. sub 50$

Zoyi MD1, Fnirsi ST1 & QPLINK S1.

MD1 and ST1.. are very similar while QPLINK S1 do differ quite a lot, with more digits (tolerances) alongside more voltage & frequency ranges, and it's able to measure live voltage up around 16v (if I recall correct) and the build is quite a step up' but also more than double the cost at 47$ (incl. EU25%VAT and shipping) than the likes of Zoyi & Fnirsi.

These 3.

Yes. the MD1. will do 0.0 mOhm by shorting the tips..

how steady you gonna land 0.0mOhm is difficult to quantify from a brief test, by just holding it with your fingers.
Here is an example, but its an older FW1.7 not FW1.8 or newer.

[iet]

Please explain a few more points.
Is the calibration of the tweezers in the C,R mode carried out with shorted and open probes?
Is the calibration value remembered by the tweezers?
What you show in the video, is it before or after calibration?
What does the tweezers show with shorted probes before and after calibration, when you hold the tweezers in the normal, working position.
What is the minimum resistance shown by the tweezers in the continuity mode?
What voltage drop does the tweezers show when checking Schottky diodes of the 1N5817-19 type at a measuring voltage of 0.6 V?

[iet]

Recently, the contact of the tips of the MS8911 tweezers has become poor, in fact, metal surfaces are in contact. This affects the measurements. I made new tips from a polished brass plate. Now everything is fine.

[DaneLaw]

Please explain a few more points.
Is the calibration of the tweezers in the C,R mode carried out with shorted and open probes?
Is the calibration value remembered by the tweezers?
What you show in the video, is it before or after calibration?
What does the tweezers show with shorted probes before and after calibration, when you hold the tweezers in the normal, working position.
What is the minimum resistance shown by the tweezers in the continuity mode?
What voltage drop does the tweezers show when checking Schottky diodes of the 1N5817-19 type at a measuring voltage of 0.6 V?

All the calibration aspects, I haven't looked into..its still vanilla.
I recall I updated the fw, at one time shortly after I got it.
In continuity 0.6v = 0.4 Ohm and 0.3v its 0.7 to 0.8 Ohm..
As highlighted in the other ST1 vs MD1 compare thread, the refresh & response rates vary drastically depending on what frequency you have it in..
in 10K instant display readings while 100Hz it takes around ½ sec before you get the reading and 1K are in between.. the beeping is instant.
1N5819 0.6v = 0.38/0.39v and 0.3v = 0.22v.  [MD1 FW1.7 1K] while Fnirsi ST-1 FW1.5 and same 1N5819 0.6v = 0.50/0.51v and 0.3v = 0.29v.

Havent checked the QPLINK LCR 1S (V1.1.0).. which do has some more features & more counts. seems to be a 10.000 count in most of the modes.
it will also do 120Hz & 100k Hz, alongside a 0.1v test mode, while in Diode-mode it also displays R and Z values..

[iet]

All the calibration aspects, I haven't looked into..its still vanilla.

Yes, there is little information about the calibration. Although it can be assumed that it is somewhat similar to ST1.
Your video has +0.4 mOhms. And the video with ANENG GN702 shows an accurate measurement of a 2.3 mOhms resistor for 3 seconds. Either they specially selected a well-tuned copy or it is not an exact copy. Maybe someone will clarify the situation over time.
In general, I think that instability in the milliohm range can be improved. Perhaps, after all, you can try other op-amps or R, C elements. At the same time, everyone understands that this tweezers circuit corresponds to a price of $ 25-30.
Now regarding the measurement of diodes. In the video with the ANENG GN702 tweezers, there is a measurement of a diode at a voltage of 0.6 V. The voltage drop is 0.3 V. I asked you to measure the voltage drop on the Schottky diodes. According to the datasheet, they have +/- 0.2 V.
So something doesn't add up here. Either some changes were made to ANENG, or this is a diode with a voltage drop of 0.1 V.
I have already written about this mode before. The ST1 tweezers have a sine signal, but it should be DC like the Pro1 Plus. Therefore, it does not measure the voltage drop of the diodes quite correctly. It is necessary to make this mode like multimeters, with a fixed DC voltage. Otherwise, switching the measuring voltage will mislead the user even more.
Most likely, nothing more will happen in these versions of the tweezers. But there is a multimeter for this.
Continuity mode. 0.5 Ohms can be reduced to at least 0.1 like in multimeters. And even better, to 10 mOhms.
You have QPLINK 1S tweezers. You said that it is a little better. I looked at it closely, but there is some mistrust.
The main thing is that the information I am interested in is missing. The video shows normal measurements. There are no measurements in the milliohm, picofarad and nanohenry ranges. There are no measurements at a frequency of 100 kHz. The developer needed to show why he needed a frequency of 100 kHz. And voltage measurement is an additional option, like D in ST1.
It is better to make the measuring voltage 0.1, 0.6, 1 V.
Perhaps you can clarify the situation, it would be very interesting and useful.
Thanks for the information.

[iet]

It is not known when the necessary changes will be made to the operation of the ST1 tweezers, so I made myself a table of voltage drops on diodes. I made measurements with two tweezers, ST1 and Pro1 Plus.

[iet]

This is how I solved the problem with checking diodes for myself. I shortened the table a bit. What are the advantages?
Quick check.
Convenient when checking SMD diodes.
Possibility to sort by Vf.
No need to use a multimeter.
During the initial check, you don't need to waste time searching for datasheets.

[iet]

The ST1 manual has an addition in the diode mode concerning continuity. The previous manual does not have this.
Continuity: In diode mode, a resistance measurement of less than 50 Ohm triggers continuity.
In fact, it works like this, but. The ST1 tweezers overestimate the resistance value by 10 Ohm. It measures 40 Ohm as 50 Ohm. That is, it actually beeps at a resistance of 40 Ohm. I checked it with a multimeter. Everything is fine there, the sound signal is triggered at a resistance of 50 Ohm. FNIRSI engineers need to correct this. And at the same time stabilize the lower limit for resistance.

[iet]

Managed to significantly improve stability in the milliohms range.
Disassembled the tweezers. Washed the board from flux. Used brass bolts. Now in the working position, within a second, the readings are set to 0.0 mOhms. Zeroing is no longer necessary. Drift is only 0.1 mOhms. This is the maximum that can be achieved in this tweezers.

[DaneLaw]

Managed to significantly improve stability in the milliohms range.
Disassembled the tweezers. Washed the board from flux. Used brass bolts. Now in the working position, within a second, the readings are set to 0.0 mOhms. Zeroing is no longer necessary. Drift is only 0.1 mOhms. This is the maximum that can be achieved in this tweezers.

If you wanna give other users an indication of milliohm "stability" then still pictures leave some to be desired, when trying to relate to possible gains (differences).
Instead maybe record a small video that shows what stability you are experiencing around 0.0mOhm, as  I exampled above on the MD1, as getting the Fnirsi ST1 to show 0.0mOhm, I reckon any ST1 would do that out of the box, at least for a brief moment, but it fluctuates a lot not least under pressure, as that single connection point seemed flawed, fingescrews or not..

My ST1 unit.. will gladly show 0.0mOhm but it's far from stabilized around those minute milliohm-values and also less than what I experienced on MD1 (GN702) but also worth noting MD1/GN702 got a lot wider tips than the original incl. on ST1 [straight / bend tipcombo], and likely from changing those to a wider custom version, as you seem to have done' I would estimate to make the biggest impact on Fnirsi ST1 and miliohm stability.

[iet]

My ST1 unit.. will gladly show 0.0mOhm but it's far from stabilized around those minute milliohm-values and also less than what I experienced on MD1 (GN702) but also worth noting MD1/GN702 got a lot wider tips than the original incl. on ST1 [straight / bend tipcombo], and likely from changing those to a wider custom version, as you seem to have done' I would estimate to make the biggest impact on Fnirsi ST1 and miliohm stability.

Let's try to understand some things regarding calibration and zeroing. The Pro1 Plus tweezers store the calibration result in memory. The ST1 tweezers have a general calibration in resistance mode, which is stored in memory. But it does not have this calibration before precise measurements, that is, calibration with closed and open probes with memorization. That is why zeroing was invented. This is good, but the zeroing result is used for a one-time measurement, the next measurement will require a new zeroing. All this turns into an unnecessary routine and a waste of time. That is why I first came up with a device for zeroing and used it for some time. Naturally, I wanted to do zeroing in the normal, working position of the hand and by closing the tips. That is why I made other tips that are more resistant to abrasion and have a slightly larger contact area. In addition, I completely accidentally found two brass bolts, which, oddly enough, further improved the quality and stability of measurements. Thus, I managed to eliminate the need for constant zeroing. The photo clearly shows the difference in results with shorted brass tips when using original and brass bolts.

[DaneLaw]

Managed to significantly improve stability in the milliohms range.

I Try again...

A brief video. would go a long way, to show that "improved stability" you mentioned you have obtained, as "stills" do jack in that regard.

[iet]

A brief video. would go a long way, to show that "improved stability" you mentioned you have obtained, as "stills" do jack in that regard.

It's not time to shoot a video yet. Not all things have been used to stabilize zero. Now we can prepare for some experiments with the tweezers circuit. The next step may be to replace the op-amp and related components. Maybe you've already tried something? If so, please share the information.
Yes, and how is the calibration of your MD1 tweezers? Any interesting information?
What can you say about the calibration of the QPLINK 1S? Does it have a calibration with closed and open probes before measuring?

[iet]

There is another very cool calibration method - automatic. This was done by the engineers of the MASTECH MS8911 tweezers. It does not have a calibration mode. All measurements are carried out quickly and accurately in automatic mode, according to the specification. No unnecessary movements and time wasted. The only condition is good contact of the tips with each other, as well as with the measured component. If the engineers of the FNIRSI ST1 tweezers managed to do this, it would be just great.