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

[snorlax212]

I like that case. @Shannon!! 😉

Yes, much more safety, I will try to design a 3D printer version, that's not a big deal in theory, except suspected of "copy" 

Hi. It would be great to see a cover like this on sale. Also, spare-tips-only option disappeared from aliexpress product page. Is there any chance to see them again on sale? (both curved and plain)

[watchmaker]

Got mine today.  Thank you Shannon, these are great!  Much more convenient than test leads to deal with and changing DMM settings.  One more approach that makes the work area cleaner and safer.

I did figure out the UI pretty quickly, which for me is unusual.  So I think you cracked it. 

I really like the autohold; great for those of us with short term memory issues.

I have to take everyone else's word for the tech performance; but if they are happy I am happy.

I would not sell them without a case (hard or leather).  That would be asking for issues one year out.

Maybe ensure that they are balanced to not hit on the tips when dropped.  Not willing to drop mine to check.

[shapirus]

Received mine today, finally, with the collectible curved tips previously owned by Shannon himself! :)
Thanks, Shannon.

Now I finally have a proper tool to verify and hand-pick my smd parts before soldering (and much more than that).

Noticed a couple of minor issues right away:

R_dc mode seems to be less precise than the AC mode, but this is probably fine. What does not look right, however, is that it shows ~25 mOhm when the tips are shorted even after performing the "short" calibration, whereas the AC resistance measurement shows proper values very close to zero in this case. Not sure if it's expected or not.

SoC percentage calculation algorithm during charging looks a bit weird. When I plugged in the cable, it went from 20% to 40% in under a minute, then within a few min to 70%, then, after yet longer period, to 80%, and now it seems to be sitting there. Unless something is wrong with the battery in my specimen, it must be the SoC vs voltage values table (or formula) that's somewhat off at lower values.

...and within those few minutes while I was writing this post, it went from 80% to 90%. Really hope it's simply charging this fast, and the battery is actually fine.

Also, before I plugged in the USB cable to charge it, I checked the battery voltage in the menu, and it was showing about 3.71 V. For a Li-ion battery, this doesn't really sound like 20% SoC -- it's rather the nominal voltage, far from the near-discharged state.

[shapirus]

btw, I think that current listing's price may scare off potential buyers: in Aliexpress search, on the search results page, they will only see the very high base price and may simply ignore the listing without even knowing that there's a discount for much of this price, which brings the total back to the normal level. That's up to the seller, of course, but as for a frequent Aliexpress customer, that would be my train of thought.

[ceut]

Received mine today, finally, with the collectible curved tips previously owned by Shannon himself!
Thanks, Shannon.

Now I finally have a proper tool to verify and hand-pick my smd parts before soldering (and much more than that).

Noticed a couple of minor issues right away:

R_dc mode seems to be less precise than the AC mode, but this is probably fine. What does not look right, however, is that it shows ~25 mOhm when the tips are shorted even after performing the "short" calibration, whereas the AC resistance measurement shows proper values very close to zero in this case. Not sure if it's expected or not.

SoC percentage calculation algorithm during charging looks a bit weird. When I plugged in the cable, it went from 20% to 40% in under a minute, then within a few min to 70%, then, after yet longer period, to 80%, and now it seems to be sitting there. Unless something is wrong with the battery in my specimen, it must be the SoC vs voltage values table (or formula) that's somewhat off at lower values.

...and within those few minutes while I was writing this post, it went from 80% to 90%. Really hope it's simply charging this fast, and the battery is actually fine.

Also, before I plugged in the USB cable to charge it, I checked the battery voltage in the menu, and it was showing about 3.71 V. For a Li-ion battery, this doesn't really sound like 20% SoC -- it's rather the nominal voltage, far from the near-discharged state.

I have also found some strange things I have sent to Shannon by PM, with some ideas for improvement .
I use a (great) UM34 from RD-Tech to check every single USB Powered items I have 

=>The charging IC seems to get about 215mA when charging (with screen).
Then at 100% it slows down to 133mA to finally stops at 72mA (it may be the current to power the oled screen and IC/Screen controllers - don't know)

But, I have let it plugged because I wasn't there to unplugged it.
And after some times, battery falls down to 90% with 72mA of power drawn: I stop here because I have not understand why.

About 90min to have the 100% after unboxing it with 20% of charge (because at 100% it keeps charging a long time at 133mA ), and before the fall down .

Here are the photos I have made, you can also see the time-code.

***
For Rdc: I have sent him a PM for that: he told me that this mode has no calibration for now, so we must remove the value at hand.
That's why I haven't show this mode on my Youtube review.



Edit: I forget to upload the one with 133mA

[snorlax212]

Can someone explain me please. I measure two points on pcb (atx psu). Multimeters show ~520mV in diode mode as it should be (there is no short circuit, pn transition is present), open if probes reversed. When I measure same place with tweezers it shows short (0.04V which is 40mV) in both ways. Why is that? Tweezers measure voltage drop right with single/off-circuit diode/transistor/w/e. I have other pcbs with same behavior with tweezers.

[tautech]

Can someone explain me please. I measure two points on pcb (atx psu). Multimeters show ~520mV in diode mode as it should be (there is no short circuit, pn transition is present), open if probes reversed. When I measure same place with tweezers it shows short (0.04V which is 40mV) in both ways. Why is that? Tweezers measure voltage drop right with single/off-circuit diode/transistor/w/e. I have other pcbs with same behavior with tweezers.

Tweezers in Diode mode that show polarity test with forward and reverse bias waveforms therefore in-circuit tests can show another conductive path as a Short.

This is normal behaviour for tweezers and these are the occasions when a diode needs be removed/isolated for an accurate result.

[snorlax212]

Can someone explain me please. I measure two points on pcb (atx psu). Multimeters show ~520mV in diode mode as it should be (there is no short circuit, pn transition is present), open if probes reversed. When I measure same place with tweezers it shows short (0.04V which is 40mV) in both ways. Why is that? Tweezers measure voltage drop right with single/off-circuit diode/transistor/w/e. I have other pcbs with same behavior with tweezers.

Tweezers in Diode mode that show polarity test with forward and reverse bias waveforms therefore in-circuit tests can show another conductive path as a Short.

This is normal behaviour for tweezers and these are the occasions when a diode needs be removed/isolated for an accurate result.

Yea, sounds legit. I also found this comment by Shannon which could be my case:

Review video is now public

Many thanks for your video, it's the first Shannon Tweezers ST42 review video, it's awesome 

There is a problem when you did the onboard diode bridge detection.
The root cause is ST42 need to detect the direction of the diodes, so the excitation current is always changing in a period,
If the diode is in parallel with a large capacitor, ST42 can not charge the capacitors to a relatively higher voltage in a short time,
and then ST42 found the voltage between two tips is quite low, so ST42 thinks it's shorted

We will try to use a larger current and longer detection period to make it better for this case.

[tautech]

FYI, my 15+yr old ST3 tweezers behave the same for in-circuit diode tests.
On occasion I get out the DMM to confirm/reject tweezers readings but the only way to be sure of the false Short reading is to isolate the diode.
The simplest methods of isolation are desoldering (improves rework skill) or cutting a trace and later adding a solder bridge (the razor/scalpel blade technique).

In-circuit tests are always just a guide as wrong readings are common, eg. a resistor often measures less than its marked value and if/when it measures more you need investigate why.

Despite all this, smart tweezers are still my preferred component test device, SMD and/or TH.

[ceut]

Can someone explain me please. I measure two points on pcb (atx psu). Multimeters show ~520mV in diode mode as it should be (there is no short circuit, pn transition is present), open if probes reversed. When I measure same place with tweezers it shows short (0.04V which is 40mV) in both ways. Why is that? Tweezers measure voltage drop right with single/off-circuit diode/transistor/w/e. I have other pcbs with same behavior with tweezers.

I also have this behaviour.
Explanation has been done from @tautech 

When it is happening to me on some board, I simply switch to LED mode, which works in this situation as it is a simple DC test like DMM (but we have to take into account the diode polarity).

[DaneLaw]

Love the headline in this thread.
 "at much lower cost" in regards the price the last few months and there is clearly massive stock at each bundle, but then again, they could ask 60.000 smackeronies, their product, their price.!
Working & manipulating the price is a tactic that some vendors use.

But has OP given any explanation on why they are trying to give "new buyers" the impression that the products price-norm is +600USD  (incl. VAT)
for a moment I recall there was an AliExpress coupon, that indicated, a massive discount, and the price would be halved to around 300US - if you hurried.

@Shannon is it a speculative tactic this price manipulation or ?   https://aliexpress.com/item/1005004239869204.html?
Asking since' a few users / possible buyers have been highlighted over the weeks, but no response even though you clearly are reading & thanking later posts.. 

[shapirus]

Here's how it looks for me, and I guess it's how it is supposed to be, with that coupon, (but even this is a strange approach, if you ask me):

[thm_w]

Probably a mistake, but, you can use current aliexpress coupons for another $8 or $20 off, shown in this sellers listing: https://www.aliexpress.com/item/1005006266374282.html

[KungFuJosh]

but even this is a strange approach, if you ask me

Maybe they're low on stock or something. 🤷

[ceut]

Here is the answer I have had from @Shannon about the price increase 1 month ago:

Question from me:
"Another question after checking your topic, and the last messages from users (one of them would like to buy it) : it seems your tweezers has increased very much in its price 
Is it aliexpress that has done that ?"

Answer from @Shannon from 10 january:
the default price is 35% off , which is the early bird price, and you know three years later, the early bird price is still there
And I set the price to 30% off, one reason is Aliexpress would punish sellers who can’t provide logistics information within 48 hours, oh my god "

[Shannon]

The Spring Festival holiday has just ended, and this price seems to be confusing for more people, and as you mentioned, this high coupon may introduce the trouble of customs.

Now it has returned to the price before the adjustment. hope you like it 

[Shannon]

Thank you for your design, which gave me the courage to "copy" it again

The picture is a sample of my latest ST42 cover, obtained through 3D printing,
but I still feel it is not elegant enough, the surface is not smooth enough, and the color is not really black.

But if you need it, I can 3D print it and send it to you, provided that you may have to pay the postage yourself.
Recently, some manufacturers have discounts, and the cost of 3D printing is close to 1 US dollar.

Also, if you guys have any good suggestions please let me know to make this cover more beautiful, maybe add some Chinese restaurant sayings
For example
"Is it not delightful to have friends coming from distant quarters?"
"Man with hole in pocket feel cocky all day"

BTW, I haven't figured out how to make it compatible with curved tweezer tips. In my mind, it looks more fancy.

[KungFuJosh]

maybe add some Chinese restaurant sayings
For example

I got this one recently. 😉

[ceut]

Thank you for your design, which gave me the courage to "copy" it again

The picture is a sample of my latest ST42 cover, obtained through 3D printing,
but I still feel it is not elegant enough, the surface is not smooth enough, and the color is not really black.

But if you need it, I can 3D print it and send it to you, provided that you may have to pay the postage yourself.
Recently, some manufacturers have discounts, and the cost of 3D printing is close to 1 US dollar.

Also, if you guys have any good suggestions please let me know to make this cover more beautiful, maybe add some Chinese restaurant sayings
For example
"Is it not delightful to have friends coming from distant quarters?"
"Man with hole in pocket feel cocky all day"

BTW, I haven't figured out how to make it compatible with curved tweezer tips. In my mind, it looks more fancy.

Mine is here    https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg5282746/#msg5282746
I'm interested in this type of cover too 
I think you could slim a little the tip of the case, something like the .jpg mod I have done quickly 

Also, any news for new fimware ?

Thanks 

[ceut]

[ Diode Mode Bug ]
for @Shannon to check

I have checked the diode mode with my DSO, and the test signal seems to be buggy 

Could some of you check the signal too ?
That would explain some inconstancy in the diode result.

[shapirus]

Same thing here.




Zoomed out:

[Veteran68]

[ Diode Mode Bug ]
for @Shannon to check

I have checked the diode mode with my DSO, and the test signal seems to be buggy 

Could some of you check the signal too ?
That would explain some inconstancy in the diode result.

Same.

[ceut]

I have sent a PM to Shannon for this strange behaviour.

Also, I give you the list of all proposal I have made by PM to Shannon for firmware improvement:
(but I don't know if these ideas will be implanted    )
1) Shannon told me that the Hardware is 100kHz compatible, so hope to have this.
2) Rdc: add a "quick" Delta/REL function with Joystick Up or Down
           (as these button doesn't do anything on Rdc mode).
3) Rdc: in general calibration menu, add Open and Short calibration.
4) Diode mode:
   - Short beep to tell good diode value (Voltage between 0.45V and 0.8V)
   - Double short beep for schottky (Voltage between 0.1V and 0.45V)
   - Continuous beep for dead diode (when shorted)
5) Change icon in Auto-Mode, as we don't really know when we are in AutoLCR mode or not.
    (the Inverted "A" is showed breafly at the beginning, and then replaced by the mesured value)
    I have attached moded photo of screen with my simple idea for that:
    Inverted letter in AutoLCR mode, compared to normal letter in manual mode).
6) Shutdown on battery-charging at 100% if it is possible, to save Oled display.
7) Modify Diode test signal (From Shannon: "change the voltage first and then enable the output")

List of "bugs" (?) :
a) Strange behaviour of Battery charging
b) Diode test signal

Thanks 

[Shannon]

[ Diode Mode Bug ]
for @Shannon to check

I have checked the diode mode with my DSO, and the test signal seems to be buggy 

Could some of you check the signal too ?
That would explain some inconstancy in the diode result.

Hi ceut,

Do you want to confirm whether the waveforms of positive and negative pulses are reasonable?

Maybe the answer can be found in the historical replies, but it is indeed too long ago and it is not convenient to find. Let us discuss it again.

The diode mode supports forward diode or reverse diode identification, so forward and reverse excitation need to be provided in sequence.
The advantage is that it can identify the reverse direction of the diode more intelligently.
The disadvantage is that when a large capacitor is connected in parallel in the DUT, a short will occur, short or other mode will appear.

So the diode mode does not support the measurement of diodes connected in parallel with large capacitance.
If you want to confirm that the direction of the diode which is parallel with a large cap, as mentioned by tautech,
we can use LED mode, it is a unidirectional excitation voltage, which can slowly fill the large capacitor until the diode can conduct.

As for the positive pulse, there is a small negative pulse immediately next to it.
When switching, the enable is turned on first and then the voltage is adjusted.
It's not a bug, but is not as elegant as we want, we will modify it to change the voltage first and then enable the output

[ceut]

Hi ceut,

Do you want to confirm whether the waveforms of positive and negative pulses are reasonable?

Maybe the answer can be found in the historical replies, but it is indeed too long ago and it is not convenient to find. Let us discuss it again.

The diode mode supports forward diode or reverse diode identification, so forward and reverse excitation need to be provided in sequence.
The advantage is that it can identify the reverse direction of the diode more intelligently.
The disadvantage is that when a large capacitor is connected in parallel in the DUT, a short will occur, short or other mode will appear.

So the diode mode does not support the measurement of diodes connected in parallel with large capacitance.
If you want to confirm that the direction of the diode which is parallel with a large cap, as mentioned by tautech,
we can use LED mode, it is a unidirectional excitation voltage, which can slowly fill the large capacitor until the diode can conduct.

As for the positive pulse, there is a small negative pulse immediately next to it.
When switching, the enable is turned on first and then the voltage is adjusted.
It's not a bug, but is not as elegant as we want, we will modify it to change the voltage first and then enable the output

Hello Shannon 
Yes, I totally understand how it works previously, even before I bought mine 

The 2 stranges things I wanted to point out were:
1) the negative voltage spike previous to the positive voltage test.
2) the positive value bigger than the negative one.

=>You have explained why, and found a solution for getting around it, thank you 

Now we have to wait for firmware