Design a New Precision LCR Tweezers with Much Lower Cost 【Shannon Tweezers ST42】

[ceut]

For AliExpress, I have simulated a new order for delivering in France, it seems to be OK for me, even the price and the shipping cost (it was about 15€ lower when I bought it for my 2023 christmas gift  ).

I don't really understand what is happening on their side, but I know they never had answers to real problem (example: I was having a problem with my Paypal account, I have asked them many times and I hae never had a single resolution, and after 1 month my problem has been fixed without them - I don't know how)

[valcher]

@ceut
When I ordered tweezers in the store, a warning came out - “you can only purchase one item.” I don't need two or more, I buy only for myself. The price of the tweezers was the same as yours. Now, if I go to the store under my account, the price is 40% higher, if a wife, then the price is low.
Most likely the product is limited and there are some temporary restrictions on accounts.

[mawyatt]

WRT making milliohm impedance measurements with any instrument. Getting Reliable Repeatable measurement results is difficult even for Bench Lab Grade LCR Meters.

We must remember that with a milliohm resistor with a 10ma test current, the measured voltage is only 10uv!! Even with a 1 amp test current this is only 1mv!!!

Don't think it's quite fair to be asking Tweezers of any kind to delve into this very low impedance area and produce very accurate and repeatable results since they likely can't produce enough test current to create a respectable DUT voltage for the measurement.

Of course we may be all wet on this as we don't know exactly how the measurements are conducted on various LCR type Tweezers!!

Best,

[Sparrow]

Regarding the mentioned battery discharge issue, I investigated the behaviour of the instrument on a daily base and finally, I'm pretty sure it was my own fault...
When not in use, I kept the tweezers in the supplied box while it also contained the folded "quick reference chart". Since the "joystick" button projects from the body of the tweezers, as long as there's only the foam padding opposite to it with the lid of the box closed, everything's fine. But if the relatively stiff paper of the quick reference chart presses against the joystick, it could very well depress it and cause the discharge problem. Investigating the chart more closely, I found traces of a depression right where the joystick would be if the chart is slided towards this edge of the box, so I assume this was actually the case.

From now on, I make sure that the chart is not covering the joystick when I close the box. No further problems observed since... 

So is the issue that the button being pressed turns the tweezers on, or that it just draws significant current by virtue of being depressed?

If the former - should be able to be fixed with a different, more robust power up method, e.g. move left, right, left, right or something else.

If the latter, then does anyone have a problem when it's in the leather case - does the case push the button?

[KungFuJosh]

It's fine in the leather case, I leave it in there 99% of the time. The leather case has a cutout so it doesn't mess with the power button.

The power button design is fine as it is, it would be weird if it was different.

[dibro]

I have no problem at all with using the leather case, Use it all the time.
But you have to take care that nothing is pressing in the case where the button is located.

[Shannon]

With the help of @Sorama, we finally solved the problem of order failure, and we are very sorry for the impact it caused.

We guess the specific reason is that the AliExpress platform launched a discount coupon activity, but the discount coupon was invalid, and then the order was closed.
At the same time, the setting of ST42 is that the store discount is only allowed once, resulting in subsequent orders:
1. When using the discount coupon, it will be prompted that the discount coupon is invalid.
2. If the discount coupon is not used, the order will be automatically closed.
It looks like that a problem within AliExpress was triggered, but they did not pay enough attention to it.
In the end, it seems that there is no problem between the buyer and the seller, but the order cannot be completed.

We modify the store discount using times, for those auto cancelled buyer can finish the order on Aliexpress platform now.

Thanks a lot for Sorama and valcher help

We found a bug in AliExpress, it caused us losses, but it seems that we will not get compensation or gifts like Shannon Tweezers :'(

[shapirus]

So I've just watched a review on the Zoyi ZT-MD1 LCR tweezers, this one:



One noticeable feature that it has is continuity buzzer. I can easily see how it may be handy when poking around at a circuit board under inspection: you won't have to reach for the regular DMM to test continuity when everything can be done using just the tweezers.

I think it might be nice to have this function in the ST42 too. As far as I understand, it should be fairly easy to implement it in firmware. The beeper is rather weak, but it may still be okay. It could be implemented as a configurable option to enable it in auto mode (and R mode as well), and the logic would then be simple: if enabled, then beep if we're in the manual or auto-detected R mode and the measured resistance is lower than say 10 Ohms.

[Martin72]

I don't know whether a continuity test function makes sense with the mechanically very limited path of the measuring tips.

[shapirus]

I don't know whether a continuity test function makes sense with the mechanically very limited path of the measuring tips.

"...let's see if this SMD cap is shorted"

[dazz1]

Hi
Rob of Tautech sold me a set of Shannon ST42 smd tweezers.
Up to now I have got by with a cheap Chinese component tester, but they are hopeless for smd work.  I rarely use thru hole components these days and using multi-meter sized probes is harder than it should be.
I don't need ultra precise but the ST42 is more than accurate enough for my needs.  Actually quite impressive performance from such a small device. 
It has a good display and a lot of functionality packed into a very small space.

I designed and printed a 3D stand based on the Gridfinity storage system I have adopted.  It can now stay on the bench where it is easily accessed while being protected.
The stand holds the test board.  The case and spare parts stay in the case.  I am going to fit a USB-C dust plug.

[Sorama]

My tweezers arrived last week.

When using the ‘short’ function (or diode) there is no beep, which I find pretty annoying to put it friendly.

Is my hearing that bad?
It does beep when starting up, but even then I have to put the body into my ear…

How do yours beep?

Sam

[watchmaker]

Shannon helped me trouble shoot this to a dead end.  But I figure my hearing is so bad (chainsaws long before PPE was recognized) that I cannot hear thrushes and spring peepers it was an irrelevant function.  Monster audio cables are lost on me as are tube amps.

So, while the beeper is dead, it makes no matter to me.

Regards,

Dewey

[Sorama]

Tnx.

So the diode function should beep?
If not—> faulty tweezers ?

[ceut]

Here are some answers.

I have already asked @Shannon about some ideas here, including all beep functions:
https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5236254/#msg5236254

https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5345456/#msg5345456

He has replied here:
https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5345870/#msg5345870

And by PM, I copy you his answer:
">For Resistor mode:
  - continuity beep with low R value
you know, we need to set the beep mode when use DMM, and the low R value is not an accuracy, such as some DMM boudary is 30ohms.
But ST42 could detect 30mohm resistance, how to chose a nice value as the boundary makes most people feels nice and not complicated is hard to balance.

One design rule is makes life simple   add an independent beep mode for test may be acceptable"

[KungFuJosh]

Tnx.

So the diode function should beep?
If not—> faulty tweezers ?

The diode function does not currently beep, it displays the results on the screen.

[Sorama]

Tnx, that explains.

@ceut,
Tnx.

[dazz1]

Here are some answers.

I have already asked @Shannon about some ideas here, including all beep functions:
https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5236254/#msg5236254

https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5345456/#msg5345456

He has replied here:
https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5345870/#msg5345870

And by PM, I copy you his answer:
">For Resistor mode:
  - continuity beep with low R value
you know, we need to set the beep mode when use DMM, and the low R value is not an accuracy, such as some DMM boudary is 30ohms.
But ST42 could detect 30mohm resistance, how to chose a nice value as the boundary makes most people feels nice and not complicated is hard to balance.

One design rule is makes life simple   add an independent beep mode for test may be acceptable"

I haven't heard my tweezers beep, and I didn't know they could, so I haven't missed that as a feature.
So one option for setting beep threshold values is to allow for user selection of the threshold.  Perhaps in log steps. No Beep, 100mOhm, 1 Ohm, 10 Ohm.
Is there sufficient user demand for such a feature?  I would use a beep, but I don't need it.

[ceut]

I haven't heard my tweezers beep, and I didn't know they could, so I haven't missed that as a feature.
So one option for setting beep threshold values is to allow for user selection of the threshold.  Perhaps in log steps. No Beep, 100mOhm, 1 Ohm, 10 Ohm.
Is there sufficient user demand for such a feature?  I would use a beep, but I don't need it.

I always use the "auto hold" function which I find super useful and great     (I have also this on my DMM and use it a lot)
This function send a Beep when it has made a correct sample before freezing it on screen, with that I can read the value easily on the screen.

You can try this feature, and also you can adjust the beep level in the menu.

In other normal mode, the beep is not used (yet ?) .

[dazz1]

Hi
I found the beep setting so that is on.  Haven't found the auto-hold yet but it looks useful.

I have been thinking the top of my could-have list of features would be Bluetooth for connection to a phone app.
I got a smart watch today, and it won't even work unless it is setup to be linked to a phone. 
Adding Bluetooth would almost certainly require a design modification and a lot of new software, so probably not a viable option.
Definitely falls into the category of desirable, not essential.

[valcher]

Dear @Shannon, is it possible to add a Bluetooth module to the USB-C socket of the ST42 tweezers?

[ceut]

As I have received a "FNIRSI" HRM-10 Battery Internal Resistor tester and recalibrated it with a Keysight U1272A DMM (too much number on the HRM-10 tester, but after calibration it seems good at reading voltage values), I have made some strange tests after coming back at my little apartment

It seems that all Battery resistor tester are using a 1Khz signal check, so the strange idea I have had is testing ESR of capacitor with these tools   

Here are the results (some surprise too see), the master reference is of course the ST42 

Tools: Genuine YR1030 from Vapcell // HRM-10 // ST42 // DS4T252

You will see the signal output of each one with the great DS4T252, then the mesured values.
I use 2 capacitors: a brand new 1000uF/35V Nichicon from Mouser, and a dead 1000uF/25V coming from my Beringher MiniMon800 Audio Router.


Signal output of the ST42 is amazing Photos are taken with auto-hold enabled (as always on mine  )

Also after a little time, I saw that the 2 testers starts to charge the capacitor.

[Shannon]

Tnx.

So the diode function should beep?
If not—> faulty tweezers ?

Diode function without beep reminder.

If you enable the HOLD function, the beep will indicates that the value is locked.
And the beep will become shorter and shorter, and if the measurement is continuous, the result will usually be less noisy (because of the continuous measurement).

[Shannon]

I designed and printed a 3D stand based on the Gridfinity storage system I have adopted.  It can now stay on the bench where it is easily accessed while being protected.
The stand holds the test board.  The case and spare parts stay in the case.  I am going to fit a USB-C dust plug.

Very impressive design.

To thank you for your advice, please let me know if there is anything we can do to help you, or if you need any accessories, we can provide them to you.

Can you share this ST42 bracket with us? It would be best if you could put your personal logo on it.
I can 3D print a batch and provide it to those who need it.

[folays]

I ordered a ST42 I am interested in being able to somewhat qualify/gauge the "fried or not ?" status of some capacitors, in-circuit, without always needing to desolder them.
I and my friends & family often have some items or appliances which always seems to fry due to corners cut on the BoM.

Like, on multiple cheap electric heaters bought at the same manufacturer, a capacitor after some diode bridge rectifier, had been choose by the manufacturer at a rating of 275 V (our mains AC is 230V +/- 10%), of no-name or similar quality. I replaced those 275 V caps by 350/375 V+, and they work again...

The capacitor was used to power the very very small PCB handling the controls and the small monochrome LCD.
The appliance is powered on by a "soft" button, I think it maybe has some implications to forcibly always being powering some IC.

At the time on some forums, some people said that if we were "unlucky" to "power on" the heater at "the wrong time" of the AC sinusoidal (which happens 100 times per second...), the capacitor which is rated too low would suddenly charge (it's a cap!) at a high current, at high rectified DC.

Well anyway, it was just for the anecdocte ;
- A LNK304GN fried during storm & lightning
- a remote parking lot door that the building maintenance company says it doesn't work anymore due to being too old, which I suspect they have in fact fraudulently removed from the associated rolling codes
- a pool robot which card has taken some water, and may be salvaged
- an air conditionner PCB which sometimes shut off after some minutes
- a remotely controlled garage door where one of the two motors door aren't anymore powered (motors work), so it's the relay or whatever which I didn't yet identified

Some stuff to diagnose !