Your DER/IET DE-5000, DE-6000, MS5308 has this strange behaviour?

[BravoV]

I believe Mastech MS5308 has the same chipset as DE-5000.

Calibrated before starting the measurements, results attached below, hope this helps.

[Carrington]

Thank you very much!

But, I think that such resistances are not the most appropriate to make this test. However, I don't know their typical parasites values.
To me seems more logical to use a smd one, without any aditional wire. Ie, just a SMD resistor.

Additionally, your LCR can't zero their Ls below 30 nH? 

"BravoV", please don't worry about. Definitely, seem that all this stuff don't matter to anyone.

Thanks for your time. 


DER DE-5000 to the trash!

[AlfBaz]

Just tried this on my DE-5000 and got reasonable results if that online wire inductance calculator is anything to go by.
Opened it up and it's a version 5

[Carrington]

@ AlfBaz: Thanks, but, what you've tried exactly? Only the wire?

[AlfBaz]

Didn't have 1ohm resistor on hand, closest was 1.2 5% carbon film.
Unmodified TL-21 and ran the cal procedure

At 100kHz:
- leads shorted ESR = 0.00ohm Ls = 0.000uH
- 10mm of .68 tinned solid copper wire ESR = 0.00ohm Ls = 4nH (should be 6nH)
- one lead right up against resistor the other 10mm away from resistor ESR = 1.19ohm, Ls = 0.031uH (31nH)
- both leads up against resistor ESR = 1.19ohm, Ls = 0.015uH (15nH)
- both leads on wire, right next to each other ESR = 0.00ohm, Ls = 7nH which seems to indicate inductance of the TL-21 alligator clips

[BravoV]

Carrington, my pleasure.

Additionally, your LCR can't zero their Ls below 30 nH? 

"BravoV", please don't worry about. Definitely, seem that all this stuff don't matter to anyone.

Its like permanent offset developed thru time  , and no, I'm not worry cause it seems like the offset is stable and constant, verified using my Fluke PM6306 benchtop LCR meter.

Most of the times I used this Mastech for quick and brief measurement only.

[The Electrician]

 My DE-5000 exhibits this same behavior.  At 100 kHz a 1 ohm resistor plus some lead length measures about 140 nH.  A 10 ohm resistor measures 152 nH.

Both resistors measure around 15 nH on the Wayne-Kerr.

[Carrington]

My DE-5000 exhibits this same behavior.  At 100 kHz a 1 ohm resistor plus some lead length measures about 140 nH.  A 10 ohm resistor measures 152 nH.

Both resistors measure around 15 nH on the Wayne-Kerr.

For the love of God! THANK YOU THANK YOU THANK YOU!

[Carrington]

Today I received a new response from DER (thanks). You can see it at attachments.
It is the answer to the first three messages of this post (more or less).
Honestly, I am very grateful for the effort they have made, but I think they have not understood me.
I know that my English is far from being close to be good enought, but it really is so bad?

[Carrington]

And now...
How do I explain all this to DER? 

[Carrington]

@ AlfBaz: Thanks.

- both leads on wire, right next to each other ESR = 0.00ohm, Ls = 7nH which seems to indicate inductance of the TL-21 alligator clips

Probably that is due to fixture errors.

See the page 23 on this document (Effect of Test Fixture Inductance): http://www.cliftonlaboratories.com/Documents/AADE%20Reveiw.pdf

[PedroDaGr8]

And now...
How do I explain all this to DER? 

It is a long shot but you can try enlisting the help of some of the native Chinese speakers on this board. They might be able to better translate what you want to say into Chinese, getting rid of the language gap between you and Der EE.

[D3f1ant]

It weird that it seems to read fine with a 2 ohm leaded 1/4w resistor but not with a soldered 1 ohm smt one. I'm sure it's  some kind of firmware bug at a range crossover point maybe. I've never experienced a 'problem' in real world usage, so the problem isnt bad enough that I'd toss it in the bin and buy a Keysight meter.  I expect and accept there maybe (will be) firmware problems with cheap gear.

[PedroDaGr8]

It weird that it seems to read fine with a 2 ohm leaded 1/4w resistor but not with a soldered 1 ohm smt one. I'm sure it's  some kind of firmware bug at a range crossover point maybe. I've never experienced a 'problem' in real world usage, so the problem isnt bad enough that I'd toss it in the bin and buy a Keysight meter.  I expect and accept there maybe (will be) firmware problems with cheap gear.

Considering the Keysight handhelds use the same ICs as the Der EE AND lack four write measurement, they aren't necessarily an upgrade. The bigger thing is that the IET labs model is the exact same as the DE-5000 and if this bug exists, it will exist in that one too.

[Wytnucls]

The Keysight meters don't use the Cyrustek ICs.

[Carrington]

It is a long shot but you can try enlisting the help of some of the native Chinese speakers on this board. They might be able to better translate what you want to say into Chinese, getting rid of the language gap between you and Der EE.

That's a good idea. I'll try. Any volunteer?

[Carrington]

It weird that it seems to read fine with a 2 ohm leaded 1/4w resistor but not with a soldered 1 ohm smt one.

Yes, very rogues! Why did not they use 1 ohm resistor? 

I'm sure it's  some kind of firmware bug at a range crossover point maybe.

Yes, maybe a wrong value on one interpolation table, or something like that.

The problem isnt bad enough that I'd toss it in the bin and buy a Keysight meter. 

That is relative.

I expect and accept there maybe (will be) firmware problems with cheap gear.

Yes, this is an "economic" instrument, and designed and made in China, but that should not be an excuse.


Maybe they never will recognize this fault, especially if only they can load a new firmware.
Also, if all the IET meters have this bug, what will be their reaction?

[Carrington]

The next test is irrefutable, see the following posts, and judge by yourself.

[Carrington]

Enhanced test fixture, both sides:

[Carrington]

Calibration test:

[Carrington]

Two resistors (connected in series), 0603 case, 1 ohm, 1%:

[Carrington]

And finally each resistor (independently):

[jpb]

I calibrated as shown in the first picture. Measured one section of the leg getting 50nH.
Measured from the ends of the resistor as shown.

Measured right by the resistor and the inductance goes up!

Assuming the true value is around 13 nH then the reactance part at 100kHz is only around 8 mohms so a 1 ohm series resistance swamps it I guess.

The rule of thumb that we used for bond-wires at microwave frequencies was 1 nH per mm.

[Carrington]

@ jpb:

Thanks.

That was my first thought, but we know nothing about its HW.
Let's assume that its HW is unable to discern, then the specifications given by DER are a false.
But what happens with IET, also lies? Remember that they are using the same hardware.

Honestly, I don't know what to believe.


In addiction, another thing that I thought when I read their last answer: How the hell DER can say that my DE-5000 has any problem from measurements made with another meter? It's absurd!

[KMSL]

DER DE-5000   CAL  with  TL-22 SMD tweezers. Manual Ls at 100kHz. Tip of tweezers joined  0nH  ESR 0 Ohm . SMD 1206 resistor 1R0   14nH  ESR 0,99 Ohm. With 1,3 cm wire Al  Ø 0,6mm   31 nH   ESR 0 Ohm.  And finally joined:  wire+Resistor 1R0  31 nH ESR 1 Ohm.  I think TL-22 are OK, but TL-21 are fake.