LCR Tweezers test and analysis (HP-990, DT71, ST5S...)

[indman]

Disadvantages:
1. A little expensive
2. The structure design is the best LCR tweezers I have ever used, but there is still a gap between real tweezers
3. Although it is very accurate, it does not support self-calibration, which may be a disadvantage

Another disadvantages is that it does not have a test frequency of 100 kHz.
Tweezers of similar cost have such an option.

[2N3055]

I have LCR Pro1. It has self cal, diode mode that can light up LEDs, DC resistance mode...
Goes to 100kHz, has setable voltage levels from 0,2 to 1 V and is a proper impedance analyser.
Works well, and is quite accurate, form what I could verify..

As Tautech says, if I need to measure LCR, (SMD or not) it is first thing that I grab... It's just so convenient and easy...

If it breaks, I would get another one quickly.

[indman]

2N3055,can you make a video of how your tweezers work when measuring low impedances?
I am interested in the stability of the readings of this device. 2-wire measuring circuit for tweezers! Stability 4 digits after the decimal point is a random number generator!

[bateau020]

As I have the same tweezers (LCR pro1 plus), I can chime in. These tweezers are really stable when the device under test is not ambiguous. Sometimes you have to force it to C or L tests, but in general, the tool is very reliable, versatile and fast. I prefer it over my DE-5000 clone.
Attached is a video of the tweezers on a 1 ohm resistor. (in a zip, don't know how to quickly add a video outside of pushing it to youtube or the like)
As you can see, some noise, but not too bothersome.

[indman]

bateau020,there is no noise on your video, but a random number generator in the last 2 bits.
Can you measure the resistance with 10-20 milliohms with your tweezers?

[2N3055]

bateau020,there is no noise on your video, but a random number generator in the last 2 bits.
Can you measure the resistance with 10-20 milliohms with your tweezers?

Noise IS the random number generator, the original one...

You can measure miliohms, but it won't be as stable as dedicated miliohm meter  and kelvin clips.

You will never have stable milliohms on a tweezer with contact surface of fraction of millimetre square, and hand regulated pressure.
You need clips with bigger contact surface area and spring to achieve semi stable and repeatable pressure.

[indman]

You can measure miliohms, but it won't be as stable as dedicated miliohm meter  and kelvin clips.
You will never have stable milliohms on a tweezer with contact surface of fraction of millimetre square, and hand regulated pressure.
You need clips with bigger contact surface area and spring to achieve semi stable and repeatable pressure.

Do you have such devices that you listed? Did the manufacturer of this tweezers put these extra contacts in the kit with the device? Otherwise, what are these 2 additional unstable digits? Indicator? Marketing?

[2N3055]

You can measure miliohms, but it won't be as stable as dedicated miliohm meter  and kelvin clips.
You will never have stable milliohms on a tweezer with contact surface of fraction of millimetre square, and hand regulated pressure.
You need clips with bigger contact surface area and spring to achieve semi stable and repeatable pressure.

Do you have such devices that you listed? Did the manufacturer of this tweezers put these extra contacts in the kit with the device? Otherwise, what are these 2 additional unstable digits? Indicator? Marketing?

I will try to explain this gently, because I know sometimes it is hard to express yourself in foreign language.
Your tone fells sarcastic and not very nice  and I am not certain what do you want with all these questions.
I don't know if that is intentional or you just struggle to find proper words in foreign language.

I didn't make those tweezers and have no idea why manufacturers implemented so many decimals when they are not even necessary.
In datasheet they specify all technical specifications, and device certainly perform better than specified..
I personally would like if they would have less digits because it is not useful or accurate to displayed number..

But I got used to it, know how to read what I want and I don't care. It doesn't make it less good or useful, although I agree with you that it is silly.

As I said I didn't make those tweezers and have no connection to manufacturer whatsoever.  I speak from my own experience and I paid for it with my own money.

If I had a chance to buy better tweezers for half the money, I would buy it gladly....
If you know the better, cheaper, ones, please share with us... I'm interested.

Regards,

[bateau020]

In theory it is possible to equip these tweezers (and the LCR Reader, the ST5S, and probably others) with 4W kelvin probes. See the attached image.
But you cannot simply buy them. The makers of the "LCR-Reader" have an extension cable that extends one end of the tweezers, via a kelvin cable (LCR-PC). But it ends in a simple probe again. Therefore: same problem.
There is a big reason you will not see milliohm measurements for this type of instrument: it requires larger currents if you want more precision. So even if possible, you would eat batteries like crazy.

Just use a dedicated instrument. Even my DE-5000 clone with 4W kelvin clips is not what I use for milliohm measurements. I just pump large currents through it and measure it the hard way, with 2 multimeters. But you could also get a good bench MM.

[indman]

I personally would like if they would have less digits because it is not useful or accurate to displayed number..
But I got used to it, know how to read what I want and I don't care. It doesn't make it less good or useful, although I agree with you that it is silly.

I also agree with you and did not want to offend you as the owner of this device. But I am critical of when a manufacturer (seller) for marketing purposes
does stupid things that customers don't need.
I know of a few really serious tweezers that are worth the cost, like the HB-14 or the newer HB-15.
But I don't know if these tweezers are sold in your countries, since the author and manufacturer of these devices is from Russia.

[bateau020]

I know of a few really serious tweezers that are worth the cost, like the HB-14 or the newer HB-15.
But I don't know if these tweezers are sold in your countries, since the author and manufacturer of these devices is from Russia.

Never heard of them before. The only link I found is this: https://www.electronicspoint.com/forums/threads/smart-lcr-tweezers-lcr-pro1-russian-rlc-tweezers-hb-14.291164/page-4. But unfortunately that thread has some very contrasting information in it, and does not look very balanced. Will read up on them some more.

Added:
They are also known as NV-14 it seems.
And have been mentioned here before: https://www.eevblog.com/forum/testgear/tweezers-for-low-impedance-capacitors/
Manufacturer website: http://rlc-esr.ru/index.php/en-us/multimetr-pintset-nv15
But the manual only seems to exist in russian.

[indman]

bateau020, read all 5 pages of this topic. Don't pay too much attention to the messages from caps is a troll known by various names. He is trying to measure a very clean ESR to 6 decimal places on a dial gauge marked with a thick felt-tip pen. 

[Shannon]

I try to explain why do these tweezers cannot support milliohm resistance.

Because they said they cannot support in the datasheet.   

ST5S has an offset spec, For the resistance ≤ 25mΩ
LCR Pro1 has a similar spec, looks like the offset is ≤ 20mΩ

[2N3055]

I personally would like if they would have less digits because it is not useful or accurate to displayed number..
But I got used to it, know how to read what I want and I don't care. It doesn't make it less good or useful, although I agree with you that it is silly.

I also agree with you and did not want to offend you as the owner of this device. But I am critical of when a manufacturer (seller) for marketing purposes
does stupid things that customers don't need.
I know of a few really serious tweezers that are worth the cost, like the HB-14 or the newer HB-15.
But I don't know if these tweezers are sold in your countries, since the author and manufacturer of these devices is from Russia.

  No worry, no offence taken, I just like to be direct and also meant no offence.

I agree that many manufacturers choose marketing over truth, and hate it as much as you..

I know about HB14 and HB15 and would have bought them, but it's not simple importing from Russia ... They seem like good instruments.
If only we could organise sales here in EU, I believe they would sell well.

Best regards

[Electro Fan]

Maybe there is an opportunity for an EEV branded tweezer.

[2N3055]

I try to explain why do these tweezers cannot support milliohm resistance.

Because they said they cannot support in the datasheet.   

ST5S has an offset spec, For the resistance ≤ 25mΩ
LCR Pro1 has a similar spec, looks like the offset is ≤ 20mΩ

With LCR Pro1  you can calibrate it out, to few miliohms...
Problem is, as I said, that tiny pointed tweezer tips cannot have low enough contact resistance to have repeatable measurements...
As you vary pressure, resistance changes in front of your eyes.. It can measure it just fine.
For larger trough hole components, if you make contact with wider flat part of tweezers, you get better results.
Also you need to clean tips with alcohol occasionally, it's gold plated and it wont corrode but it will get dirty.. 

[tautech]

Maybe there is an opportunity for an EEV branded tweezer.

Only if Dave has changed his ideas about SMD tweezers.
When he reviewed the ST3 years back he didn't think much of them yet many of us have been using them for years.

[Shannon]

Maybe there is an opportunity for an EEV branded tweezer.

Only if Dave has changed his ideas about SMD tweezers.
When he reviewed the ST3 years back he didn't think much of them yet many of us have been using them for years.

haha
I watched Dave's ST3 video again, and he was so funny  "I love Canadians!"

In fact, My friends and I have discussed this topic, and we think that a more cost-effective tweezer with similar performance may be possible now

[Shannon]

I try to explain why do these tweezers cannot support milliohm resistance.

Because they said they cannot support in the datasheet.   

ST5S has an offset spec, For the resistance ≤ 25mΩ
LCR Pro1 has a similar spec, looks like the offset is ≤ 20mΩ

With LCR Pro1  you can calibrate it out, to few miliohms...
Problem is, as I said, that tiny pointed tweezer tips cannot have low enough contact resistance to have repeatable measurements...
As you vary pressure, resistance changes in front of your eyes.. It can measure it just fine.
For larger trough hole components, if you make contact with wider flat part of tweezers, you get better results.
Also you need to clean tips with alcohol occasionally, it's gold plated and it wont corrode but it will get dirty..

Yes, I agree with you. I've also thought about this issue.
Is it possible to make tweezers tip into a pen tip like structure? Each tweezer tip is composed of two metal tips. It's cool to think of. as attached.

Another problem is that for the LCR meter, the measurement of milliohm level is limited by the amplitude of the excitation signal, it is not easy to measure, as bateau020 said

Suppose the exciting current is 1mA, the resistance is 1mOhm, and the voltage amplitude is only 1uv

[Electro Fan]

Nice illustration Shannon 👍

[bateau020]

Nice quote from another thread running now:

If the circuit in question can't take an ampere, then we likely don't need to measure it in microohms or even milliohms.  Measuring uV or nV is a lab experiment, not a something you casually check with a DMM.  A 2 degree (K) temp difference between identical copper alloys will give you a microvolt, the same difference between a stainless steel probe and an ENIG PC trace is probably in the 10s of uV. 

This dedicated low ohm instrument uses up to a 1A test current.  Some use even more.

https://www.chromausa.com/pdf/16502-E.pdf

Now that voltage (from the Seebeck effect if I remember correctly) is DC or close to DC, so measuring in AC would allow mitigation. However, its noise adds to the noise in your input stages. Add that to the varying quality of the contact (which is the main problem I think), and the proximity of a heat source (hand), and you got a situation that is not favourable.

[Shannon]

Nice quote from another thread running now:

If the circuit in question can't take an ampere, then we likely don't need to measure it in microohms or even milliohms.  Measuring uV or nV is a lab experiment, not a something you casually check with a DMM.  A 2 degree (K) temp difference between identical copper alloys will give you a microvolt, the same difference between a stainless steel probe and an ENIG PC trace is probably in the 10s of uV. 

This dedicated low ohm instrument uses up to a 1A test current.  Some use even more.

https://www.chromausa.com/pdf/16502-E.pdf

Now that voltage (from the Seebeck effect if I remember correctly) is DC or close to DC, so measuring in AC would allow mitigation. However, its noise adds to the noise in your input stages. Add that to the varying quality of the contact (which is the main problem I think), and the proximity of a heat source (hand), and you got a situation that is not favourable.

Yep, You reminded me, it is possible to obtain higher signal-to-noise ratio base on using AC excitation signal to measure impedance,

Some high-precision Wheatstone bridges use AC excitation to avoid low-frequency noise.

But if power consumption and temperature rising of large current are acceptable, DC large current is a more easy choice.

[bateau020]

Some high-precision Wheatstone bridges use AC excitation to avoid low-frequency noise.

But if power consumption and temperature rising of large current are acceptable, DC large current is a more easy choice.

Depends on the use case.
If you want to find a short on circuit board, you will need to do it in DC or a low frequency. Otherwise you will measure the caps, plus the board layout will add inductance, so you will be mislead. Just keep the voltage low enough to no to fry components. Well, you could go fancy and test through pulsed excitation, but then you are in the area of the higher end tools.
If you have 1 component that you want to test, then AC could be better.

By the way, for testing on boards in the milli-ohm range it is best to avoid tweezers: contact surface and pressure have too much influence on the measurement, and are relatively hard to control with tweezers. Use pointy kelvin probes, and they are hard to find (the battery test kelvin probes are easy to find, but they are way too large). For those who want to see how it's done, look what Robrenz did. Deep respect for his skills.

[serg-el]

I already wrote earlier in another topic, and attached photographs. 
Kelvin probes with a short distance are easy enough to make from felt-tip pens and sewing needles. 
Shielded wires.  Closed relay contacts and tracks between contacts are clearly distinguished on the boards.
  Relay resistance is higher;)
And my tweezers are HB-1.  The first of the HB series.  We have already written about them above in the topic.  (NV-14, NV-15).

[fabriciofx]

Shannon,

Please, can youy let me know when you start sell it?

Best Regards.