EEVblog #1335 - Miniware $70 DT71 LCR Tweezer REVIEW

[EEVblog]

Review of the new $70 Miniware DT71 LCR Tweezers, is it any good?
https://s.click.aliexpress.com/e/_dT6koqT

TLDR; It's not very accurate, doesn't have much resolution, limited ranges, accuracy issues between Auto and Manual modes, can't be used while charging, lose the custom charge lead and you are screwed, tilt head detection has a bit of an alignment issue, LED testing is limited, and the secondary measurements basically don't work.
But for $70 it's very handy and nothing else can touch it, and the probe design is gorgeous.
Absolutely no match for the much more expensive SmartTweezers.
Maybe they can fix some stuff in firmware to improve it.

[dr.diesel]

No go if you ask me, especially with the asinine charging setup.

[langwadt]

that it doesn't do auto polarity for LEDs could be good thing if you have to check if a bunch of LEDs are mounted the right way

I guess having two different blink frequencies for the different polarity could work too

[EEVblog]

that it doesn't do auto polarity for LEDs could be good thing if you have to check if a bunch of LEDs are mounted the right way

True, if you can't get visual confirmation.
But if machine placed then they are either all going to be correct or all wrong!

[EEVblog]

No go if you ask me, especially with the asinine charging setup.

It's the Achilles heel

[thmjpr]

Bidirectional is good for LEDs, not having it is quite annoying. Software can easily compensate if you wanted to test a row of LEDs (just have a setting for uni/bi or pulsed as you say).

Seed $59 (+~$10 ship): https://www.seeedstudio.com/Mini-Digital-Tweezers-DT71-p-4696.html
Taobao $55: https://item.taobao.com/item.htm?id=626966187557
Global specialty LCR-58 $90 (no LED test): https://www.tequipment.net/Global-Specialties/LCR-58/LCR-Meters/
Smart tweezers $120 (no LED test): https://www.amazon.ca/Pince-épiler-LCR-Reader-Basic-Compteur/dp/B07C7S9DG6/

I would buy just the tweezer portion and make some adapter leads for my DMM and LCR meter. Someone could even make a better "head" unit for it, but thats probably wishful thinking.

Some photos show a curved set of tips, but it only comes with the one tip pair included.

[Skashkash]

I think that 3 pin TRS connector is working against them for measuring. They need to tie the battery gnd (probably) to one of the tines.

So no differential. And unless they have a charge pump in the head, driving a bi-polar signal for leds is going to be tricky.

[tautech]

Smart tweezers $120 (no LED test): https://www.amazon.ca/Pince-épiler-LCR-Reader-Basic-Compteur/dp/B07C7S9DG6/

No diode test ^ so a waste of tucker !
Had a set of ST3's for some years longer than Dave and wouldn't be without them.
BTW ST3 tips can be stretched to 50mm if needed.....far wider than a DT71.

When/if they die these are the ones to get: https://www.smarttweezers.com/st5s/

$274 here: https://smarttweezers.3dcartstores.com/

[2N3055]

It looks kinda fiddly.. Not impressed...

[EEVblog]

Global specialty LCR-58 $90 (no LED test): https://www.tequipment.net/Global-Specialties/LCR-58/LCR-Meters/

I already have one of those on order, only just discovered it while editing this video.

[BrianHG]

So no differential. And unless they have a charge pump in the head, driving a bi-polar signal for leds is going to be tricky.

Why?  If each pin goes to a different IO on the MCU, you just make 1 IO high and the other low, then swap.

[tszaboo]

So the TL:DR is that it has good mechanics, and probably OK electronics, that is utterly ruined by firmware. They seem to not understand what a measurement instrument is supposed to do. Like what frequency to measure a capacitor. Not to mention, with that huge errors, I dont think I would trust a single number that comes out of it.

[Skashkash]

So no differential. And unless they have a charge pump in the head, driving a bi-polar signal for leds is going to be tricky.

Why?  If each pin goes to a different IO on the MCU, you just make 1 IO high and the other low, then swap.

Yeah, was thinking about that, and a three pin connector is just way too restrictive.
So I took a closer look at the videos and it appears that they are in fact using a four pin TRRS connector. Much better.  So ignore my last post.  They certainly could drive both tips anyway they wanted.,   

[chickenHeadKnob]

Folks haven't been commenting on the left/right display hypersensitivity to motion. This one thing can make it unusable.
My Miniware TS100 exhibited the constant erratic switching  into sleep mode bug. Made it infuriating to use. Then I  fixed it when I downloaded the opensource firmware.

[Kosmic]

Global specialty LCR-58 $90 (no LED test): https://www.tequipment.net/Global-Specialties/LCR-58/LCR-Meters/

I already have one of those on order, only just discovered it while editing this video.

The Global specialty LCR-58 really look like the Mastech MS8911 (same buttons, same functionalities), but the later one is around 48$ 

Not to be confused with the MS8910 that look the same. The MS8911 is a full LCR meter with testing frequency from 100Hz to 10kHz with secondary parameters.

[rsjsouza]

So the TL:DR is that it has good mechanics, and probably OK electronics, that is utterly ruined by firmware. They seem to not understand what a measurement instrument is supposed to do. Like what frequency to measure a capacitor. Not to mention, with that huge errors, I dont think I would trust a single number that comes out of it.

+1 to that. I am not impressed. Besides, I got Keysight's shielded tweezer accessory to my Reed LCR and it covers this with advantages such as 100kHz frequency range and miliohms of resolution.

[Microcheap]

The Mastech MS8911: http://mastech-group.com/products.php?cate=104&PNo=78#_ doesn't have the same cool looking and feel and has, at least on paper, worse accuracy specs but it seems to work well, inclusive doing in-circuit measurement and it's cheaper.

The only problem is that I can't find where to buy it that will deliver to my country.

[Kosmic]

Looking at the waveform they use for measurement I doubt you will ever see any interesting secondary parameters (ESR, Q, D). They are clearly not measuring impedance here.

[EEVblog]

Absolutely no match for the much more expensive SmartTweezers.

How are they improving over the years? Last time I used them they are pretty buggy, like showing 0.9V instead of 1V test voltage, forgetting settings after charging, and some other weirdness going on.

I had to switch to LCR Research tweezers, and so far I've yet to find anything I don't like them while being cheaper and less buggy.

I don't have the latest design unit.
The LCR research one does look good, btu the top model is not cheaper. They over a lower end models though, and at $169 and comes with a NIST cal cert is pretty darn good value though.

[SilverSolder]

The UNI-T UT116A and UT116C also have the ability to rotate the head in relation to the tweezers - at ~$20 - $30 ? they seem worth a look as well.

[Kosmic]

The UNI-T UT116C also has the ability to rotate the head in relation to the tweezers - at ~$55 it seems worth a look as well.

It's a multimeter in a tweezer form factor though. Not a LCR meter.

[2N3055]

Absolutely no match for the much more expensive SmartTweezers.

How are they improving over the years? Last time I used them they are pretty buggy, like showing 0.9V instead of 1V test voltage, forgetting settings after charging, and some other weirdness going on.

I had to switch to LCR Research tweezers, and so far I've yet to find anything I don't like them while being cheaper and less buggy.

I don't have the latest design unit.
The LCR research one does look good, btu the top model is not cheaper. They over a lower end models though, and at $169 and comes with a NIST cal cert is pretty darn good value though.

1+ LCR research. I have them now for almost two years and they work well. I use it all the time.
But they are expensive.

With LCR tweezers, next development is not more features and gimmicky stuff like autorotation, but simple design, decent tweezer part and lower prices.
DT71 has good price, and if they went to copy classic design like everybody else and made it have necessary functions and mid range accuracy (no need for 01-0,2 %) it would be hit..

[KE5FX]

The Mastech MS8911: http://mastech-group.com/products.php?cate=104&PNo=78#_ doesn't have the same cool looking and feel and has, at least on paper, worse accuracy specs but it seems to work well, inclusive doing in-circuit measurement and it's cheaper.

The only problem is that I can't find where to buy it that will deliver to my country.

I just bought one of these.  A frustrating piece of gear.  It performs much better than rated; at 10 kHz in manual mode it can measure down to the 1-10 pF range, rather than 600 pF as the specs suggest, and it can measure inductors down to the 100 nH vicinity.  But its failure to remember its control settings is a real hassle if you intend to use it in manual mode, and who the heck wants to see dissipation factor as the secondary parameter for capacitance measurement, rather than ESR?

The prong tips are oddly-shaped and don't grip components well, it takes way too much force to close the tweezers, and they don't open wide enough to measure most through-hole parts despite the notched prongs suggesting that's what they had in mind.

It's OK for the price... but it wouldn't have taken much more development to justify a higher price, let's put it that way.

[SilverSolder]

The UNI-T UT116C also has the ability to rotate the head in relation to the tweezers - at ~$55 it seems worth a look as well.

It's a multimeter in a tweezer form factor though. Not a LCR meter.

You are right, it is missing the Inductance function.  But it looks like it will do everything else, including auto detecting the type of component (R, C, D) - auto detect is in the UT116A model only apparently.

Some users may be able to live with the fact that they have to dig out another meter to measure inductance, in return for paying very little for what looks like a handy little item with a rotatable head?

[Kleinstein]

With SMD parts it is sometimes difficult to tell if a part is an inductor or resistor. So it makes sense to have at least a crude way to measure inductance.

[SilverSolder]

With SMD parts it is sometimes difficult to tell if a part is an inductor or resistor. So it makes sense to have at least a crude way to measure inductance.

Agree, full LCR capability and ability to give ESR of capacitors makes a "real" LCR tweezer a great troubleshooting tool.  However, these devices are not yet totally convincing - tiny screens, deep single click menus, rechargeable, expensive - all factors that I dislike.

So I just ordered a $19 Uni-T UT116A tweezer because I think it will be "good enough for Australia" in 95% of my use cases, for very little money, with a large screen (that can be twisted relative to the tweezers!), using AAA batteries (not Duracell obviously! ), and usable-looking controls.   It obviously has limitations - and there is only one way to find out how much they matter! 

[thm_w]

UT116 does have a 3V diode test and 21V zener test mode, which is really nice (not bidirectional). Many DMMs do not have this ability.

I don't understand the UT116C though, it has higher resolution, but less features.. what? But its cheaper ($14): https://www.aliexpress.com/item/10000342672956.html

[SilverSolder]

UT116 does have a 3V diode test and 21V zener test mode, which is really nice (not bidirectional). Many DMMs do not have this ability.

The high voltage zener mode can probably light up most LEDs, even blue ones.

I noticed that the tweezers have a big + and - on them, so you can at least see what it is doing.  (And the head can be twisted in relation to the tweezer, so you can see the screen measuring either way...)

I don't understand the UT116C though, it has higher resolution, but less features.. what? But its cheaper ($14): https://www.aliexpress.com/item/10000342672956.html

Yes, LOL, why bother making two models that are this close, instead of one model with the features of both??

To my mind, detecting the component type is a primary benefit of these kinds of tweezers so I really don't understand why that was left out of 116C...   a plausible theory might be that the C model is intrinsically slower due to the higher resolution, which would make auto scan too painfully slow to use - perhaps a better chip was out of the question for BOM cost reasons - so that's how we ended where we are, with two separate models, trading off resolution for auto scan?

[Microcheap]

UT116 does have a 3V diode test and 21V zener test mode, which is really nice (not bidirectional). Many DMMs do not have this ability.

The high voltage zener mode can probably light up most LEDs, even blue ones.

It certainly can, I have a HoldPeak HP-4070C SMD tweezers that is very similar to the UT116, although you can't rotate its head and it doesn't have the +/- signs on the tweezers but I easily fixed that with a marker.

It can identify zener diodes up to 24V. When measuring battery voltage, the tweezers will apply a 10mA load so you have a better idea if the battery still good or not.

[BU508A]

I do like the idea with that 1kHz sine generator. It could be used as a signal tracer for repairing audio amplifiers.

[firewalker]

Someone should use Madires code on this device.

https://www.eevblog.com/forum/testgear/$20-lcr-esr-transistor-checker-project/

[TheNewLab]

Global specialty LCR-58 $90 (no LED test): https://www.tequipment.net/Global-Specialties/LCR-58/LCR-Meters/

I already have one of those on order, only just discovered it while editing this video.

The Global specialty LCR-58 really look like the Mastech MS8911 (same buttons, same functionalities), but the later one is around 48$ 

Not to be confused with the MS8910 that look the same. The MS8911 is a full LCR meter with testing frequency from 100Hz to 10kHz with secondary parameters.

Yes, I got the Mastech years ago. Paid around $35 then. It's fun, played with it and used it a little. Haven't seen the Video yet, but this was my first thought. No Lith-ion battery, Larger and "Mastech green", but i imagine its pretty similar. Similar issues on accuracy, and since I am left handed, trying to read the LCD screen is a nightmare. It is designed to be used in your right hand.  LOL

[Doctorandus_P]

So the battery life of this thing is ... 2 weeks?
I also find the user interface impossible to use with a single button for everything.

The tweezer part does look nice mechanically, but the very small display which turns upside down too easily, single button,

Several years ago I bought a Mastech MS8910 and I do not use it much, but it's still running on it's first CR2032.

The tweezers on this Mastech are a bit flimsy, and you have to flatten and bend them parallel to each other before the thing is usable, but then it works quite good. It also comes in a sturdy plastic box which prevents the tweezers points from getting damaged from moving about in a parts bin.

I do not really care for accuracy of tweezers like this. As long as it can reliably distinguish components upto E24 I'm happy.
Current price seems to be around EUR 20.

[SilverSolder]

So the battery life of this thing is ... 2 weeks?
I also find the user interface impossible to use with a single button for everything.

The tweezer part does look nice mechanically, but the very small display which turns upside down too easily, single button,

Several years ago I bought a Mastech MS8910 and I do not use it much, but it's still running on it's first CR2032.

The tweezers on this Mastech are a bit flimsy, and you have to flatten and bend them parallel to each other before the thing is usable, but then it works quite good. It also comes in a sturdy plastic box which prevents the tweezers points from getting damaged from moving about in a parts bin.

I do not really care for accuracy of tweezers like this. As long as it can reliably distinguish components upto E24 I'm happy.
Current price seems to be around EUR 20.

High accuracy is an awesome bonus feature, but the essentials are:
  1) Accessible pricing.  No more than $30 for an entry level model.
  2) Usably sharp/nice tweezers, mechanically
  3) Good sized screen visible from all angles.
  4) Twisting the head is essential if the tweezers are polarized and nice if not (right/left hand, or just convenience)
  5) Must have all the buttons that are needed, and no more (and no less!)

If all the basics are there, I might be persuaded to cough up a bit more for additional features like higher accuracy, WiFi connectivity to a PC (not bluetooth!), and so on.
 

[ober]

When measuring battery voltage, the tweezers will apply a 10mA load so you have a better idea if the battery still good or not.

Little known fact: If you swap the polarity, it does *not* apply the 10 mA load, so you can get a quick check for whether the load makes a difference.

I keep an HP-4070C ($17 shipped, or a HP-990C, which is yellow but otherwise identical, $15 shipped) around at every desk.  I think I use those more than any other multimeter.  Doesn't do L, as mentioned. 

I also have an MS-8911 handy (~ $50, harder to find but worth it), which can measure at 0.1 V (i.e., does not turn on silicon), so it is more useful in circuit, and measures ESR, but is pure LCR (no LED, battery, ... checks). 

Finally, a DE-5000 (~ $100) for when I value precision over convenience. 
(I also have one of the original Bob Parker ESR meters; those were the days.)

Oh, and a couple $7 transistor testers (both the 9 V naked ones, which I also use to build some special-purpose test rigs from, and the "LCR-TC1" cased version with Li-Ion battery, $13 shipped).

Not really useful once you have one of the HP-nnnC tweezers: MS-8910.

Looking forward to finding out how the DT71 will fit into this mix... 
But did the scope image really show a 30 V peak-peak waveform?

[ober]

Looking forward to finding out how the DT71 will fit into this mix... 

Oh.  That thing is fiddly.  It is nearly impossible to not press the touch button when wrestling with a device and trying to put the tweezers into the right place...  and before you know, you are putting 1 V rms from the signal generator into the device... or activate the calibration function...

Manual says: "Note: Maximum absolute input voltage: -5V ~ 50V; Input resistance: 1MΩ."

So if you want to measure those 12 V and happen to have your tweezer legs rotated wrong, the unit is toast?

[SilverSolder]

Looking forward to finding out how the DT71 will fit into this mix... 

Oh.  That thing is fiddly.  It is nearly impossible to not press the touch button when wrestling with a device and trying to put the tweezers into the right place...  and before you know, you are putting 1 V rms from the signal generator into the device... or activate the calibration function...

Manual says: "Note: Maximum absolute input voltage: -5V ~ 50V; Input resistance: 1MΩ."

So if you want to measure those 12 V and happen to have your tweezer legs rotated wrong, the unit is toast?

I generally dislike touch controls.   Just because I touch something doesn't mean I want to activate it! 

[globoy]

Just leaving this here as an FYI for some future internet searcher.  Some connection in the tweezer section of my DT71 broke.  The tweezer section is not meant to be taken apart as Dave showed during his disassembly video.  Mine was destroyed during disassembly but I did manage to back out the schematic in case anyone ever wants to do what I did and make a new base for the display module.

The tweezer section contains 2 50mAh 3.7V LiPo cells wired in parallel (although each has a 0-ohm resistor in series with it) and a simple charging circuit.  I couldn't identify the charger controller based on its markings but it has a very common pinout and I suspect it's some version of the TP4054.  It is configured for a maximum charge current of 50 mA using a 20 k-ohm resistor connected to its PROG input.

The tip of the display connector provides power and the base ring is ground.  The tip is connected to the battery output in the tweezers and to USB 5V in the charging adapter.  The display senses the voltage and uses that info to decide if it is a meter or if it is a USB peripheral.  A voltage near 5 volts switches it to USB mode.

The tweezer negative probe is simply ground while the positive probe is connected to the inner ring next to the ground ring.  In the tweezers, the ring next to the tip is used to feed USB 5V to the charge controller VIN.

Interestingly there are two RED LEDs, each with a 1 k-ohm series resistor attached to the charge controller's low going status output.  I guess this was required to uniformly light the lens given how they wrapped the connector with a flex circuit.

I ended up salvaging the batteries, connector, charge controller and the 0402-sized 20 k-ohm resistor and mounted them all on a proto board which went into a 3D printed enclosure.  No more tweezers for me but something that reminds me of the now ancient HP 970A DMM.

[rogerggbr]

Thanks for the info and breakdown/schematic, here is what I ended up with when the batteries failed and I couldn't find the correct size.....