Products > Test Equipment
East Tester ET3502 LCR-Bridge
Martin72:
--- Quote from: mawyatt on August 12, 2024, 10:57:49 pm ---Since these fixtures are somewhat direct clones of the Tonghui TH26008A which is rated to 120MHz and states, "Applicable to: SMD devices, high frequency small capacitors and small inductances." are you implying that their TH26008A is garbage??
https://www.tonghui.com.cn/en/product_144.html
BTW what is "HF-tight"?
Honestly think Tonghui knows what they are doing and we've certainly got excellent results after modifying the clones but only to 8MHz tho :-+
Not too impressed (exposed blades in handle) with the Tonghui Kelvin Clips tho, but haven't seen any others that appear better.
Hope you get over your cold soon!!
Best
--- End quote ---
Thankyou, I hope tomorow it´s going better...
I didn't say that Tonghui's fixtures are garbage, but from an HF point of view everything is still far too "open".
I could imagine at least "sealing" the inside of the housing with HF sheet metal, perhaps even constructing a cover that can be placed on the fixture during the test.
But these are just thoughts for now.
mawyatt:
--- Quote from: Martin72 on August 13, 2024, 10:18:23 am ---
Thankyou, I hope tomorow it´s going better...
I didn't say that Tonghui's fixtures are garbage, but from an HF point of view everything is still far too "open".
I could imagine at least "sealing" the inside of the housing with HF sheet metal, perhaps even constructing a cover that can be placed on the fixture during the test.
But these are just thoughts for now.
--- End quote ---
The case and cover are sort of an RF enclosure. However, the cover must be well constructed, tight fit, and connected to the case for good RF shielding. Also applying to the BNC shell to case for a good RF connection. If you study the design the only RF exposure is with the two plunger tips, which has worked well with our experience.
You want the enclosure interior to provide space for the wire from the BNCs to the plungers, and also enough distance to each wire to have a small effective shunt parasitic capacitance. This becomes important for the movable plunger side as the wires move with the plunger the parasitic capacitance changes. If the space were smaller with wires closers to case/cover the parasitic capacitance would be higher and the capacitance change with plunger movement larger.
Note the need for a field shield between the H and L sides of the enclosure for High Z and/or Higher frequency work, you don't want the H and L wires "seeing" each other electrically. A simple "L" shaped aluminum bracket shield bolted to the case would work, or even a Cu or FR4 rectangular section soldered to the BNC ground washer assuming the washer is well connected to the case.
Suspect when you get the OEM Tonghui version at work, you'll see all the finer details they use. The clones obviously forgo many of these details to save cost, but one can recover the benefits with some additional tinkering and work :-+
Best,
mawyatt:
@ Martin,
Get some good pictures of the SH26008A (Tonghui TH26008A) if you can. As most quality OEMs they pay attention to detail, altho one could question the Guard Terminal on the REAR of the TH2830 LCR Meter ???
Best,
Martin72:
--- Quote from: egonotto on August 12, 2024, 05:33:09 pm ---Shouldn't VAC be around 0.2 mV or IAC around 100 mA?
--- End quote ---
Thanks again for this post. :-+
I simply asked ET how the VAC/IAC values come about and as always they responded promptly (which is really great).
They sent me a picture of a handwritten sketch, really cute. :D
But then you can also understand it, because in my calculations I neglected the output resistance (100 ohms).
So far so good, so understandable - but.... ;)
The engineer who drew this has made a small calculation error.
The nano value is one decimal place too low.
This has hardly any effect on the current display, but the voltage is displayed too high by a factor of 10.
So if this is the same engineer who is responsible for the software, then the same error will be found in the program.
I have therefore sent ET a picture with notes on the slip of paper.
Let's see what comes back.
Martin
mawyatt:
100 ohm source impedance is too high to evaluate low Z components like 10nH at LCR Meter frequencies. Look at the ratio between the DUT Z and the source impedance!!
This is why the TH2830 has a lower 3 ohm range (30 ohm source) and the IM3536 is lower with a 0.1 ohm range (10 ohm source)!!
Best,
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