EEVblog #1335 - Miniware $70 DT71 LCR Tweezer REVIEW

[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.....