Products > Test Equipment

East Tester ET3502 LCR-Bridge

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mawyatt:

--- Quote from: Martin72 on August 12, 2024, 05:12:57 pm ---I took a few more pictures.
It doesn't look too bad.

--- End quote ---

Martin,

That's the kind of SMD Fixture that can cause issues!

It has no internal shield partition between the H and L sections. This will cause errors with small Cap measurements (high Z) as the internal fields change with plunger location on the moving end. This will be aggravated by the ET35 since its H and L sections are reversed which means the moving plunger end is the "hot" H end whereas the normal LCR Meter orientation has the moving plunger on the "cold" L side.

Also we found this type with the two end screws on the cover use a thinner aluminum case/cover and powder coat paint the entire case and cover without any masking. This may cause less than ideal shielding between the cover and case which makes contact thru just the 2 end screws.

The other (better) type SMD Fixture we have has 4 screws to hold the cover and uses threaded inserts in the cover.

The cover you have looks like it might be sturdy enough tho, might want to ream the holes in the cover to remove the paint coating and get good contact with the 2 screws to case.

The case looks as if it's only relying on the BNC washers to puncture the paint coating to tie to the cover, this may require removing the BNCs and cleaning away the paint coating around the BNC holes for better contact.

Also check the Plunger outer cases, these form a somewhat coaxial conductor with the plunger, you want these to be firmly connected to the cover which must make a good connection the case to get back to the BNCs.

Remember to check the brass threaded rods that make contact with the plungers, ours arrived loose and it took awhile before we discovered this "surprise"!!!

Anyway, looks like you might have some reworking ahead to get this SMD Fixture up to standards for precision LCR measurements with the ET35!!! After getting things in order our modified SMD fixture has good repeatability even up to 8MHz, so these can be "coached" with a little effort into a good fixture for precision measurements.

Keep us posted on your progress.

BTW are you sure you have a cold, or just "skipping work" to have time to play around with this stuff ;)

Best,

Martin72:

--- Quote ---BTW are you sure you have a cold, or just "skipping work" to have time to play around with this stuff ;)

--- End quote ---

Unfortunately not, but if at all possible tomorrow I want to go to work - just to measure the ST2830... ;)

Martin72:

--- Quote from: mawyatt on August 12, 2024, 08:44:13 pm ---This doesn't seem correct. The DUT Voltage and Current imply ~90nH not ~10nH.

Wonder if the fixture is causing problems??

Best,

--- End quote ---

After egonotto noticed this, I looked into it again.
I'm still not entirely convinced that the values are wrong, I'll hopefully take the same choke with the fixture to work tomorrow and connect it to the ST2830.
Then record the values at the maximum possible frequency of 100kHz and measure them at home on the ET35.
I also measured a capacitor earlier, like you did on your TH2830 a page earlier.
However, 10pF, because I didn't have a 4.7pF.
The result itself is plausible, but you can't derive it from the monitor voltage/current.
I'll measure that tomorrow too, if I'm fit enough.
And it's supposed to get really warm tomorrow of all days... :P

Martin72:

--- Quote from: mawyatt on August 12, 2024, 08:37:57 pm ---That's the kind of SMD Fixture that can cause issues!

--- End quote ---

The only question is how large these can be with a (current) maximum frequency of 300 kHz.
That's almost audio... ;)
From an HF point of view, this fixation is simply garbage.
And not only this fixation, others too.
They are all not "HF-tight" ....
I already have ideas on how to change this, I will also order the ST fixture for our test field as announced - and "of course" take it apart for optical inspection.... 8)

mawyatt:
Got a Wurth RF 0603 Chip 10nH Inductor & Pulse Electronics with Standard SMD fixture and measured with IM3536 at 300KHz and 100KHz. Readings are in nH (Vdut mv/ Idut ma).

DUT Device                     100KHz                         300KHz                        1MHz

Wurth 10nH                     11.86                            11.83                          11.79
Pulse Electronics 10nH      10.34                            10.38                          10.37

With TH2830   

Wurth                              11.878
Pulse                               10.574

This is with our mentioned modified Standard SMD Fixture, swapped and use on both the IM3536 and TH2830.

Note how small the Pulse 10nH is compared to the Wurth 0603 10nH!!

Think your fixture is causing the issues you are experiencing. Just tried 8MHz and getting 11.83nH with Wurth, so the fixture is holding up well to 8MHz.

BTW Tonghui specs thier SMD fixture to 120MHz :-+

Wouldn't rely too much for low Z work tho, and why we developed the Special Split Kelvin Fixture :-+


Edit: Went back and reran with Wurth (Pulse is too small and difficult to handle) and added a couple images.

2nd Edit Removed Vdut and Idut readings, see post 137 below.

Best,                                           

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