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.