Products > Test Equipment
LCR Tweezer Fnirsi ST1 vs. Zoyi MD1
awakephd:
--- Quote from: Paul T on September 29, 2024, 06:55:07 pm ---@DCFluX 100 Hz would be best when above 1uF, looks like yours is set to 1kHz. Please recheck at 100 and see if you get the same improvement. :popcorn:
Here's some easy-to-remember rules of thumb. Once you get the general measurement at 1kHz, switch to the best frequency for better accuracy if needed.
For capacitors
10kHz for pF
1kHz for nF
100Hz for μF
For inductors
10kHz for μH
1kHz for mH
100 Hz for H
I don't know of any meters that adjust the frequency for you automatically. Most good meters work the same as these tweezers. If you get a full-sized LCR bridge, you'll also need to learn whether series or parallel method should be used for your device or circuit.
Meters with 100kHz can be more accurate at low pF or nH measurements.
--- End quote ---
Paul, thank you for this. I had not really understood the significance of the 100 - 1K - 10K settings on my recently acquired Zoyi MD1 ... and meanwhile I was getting some readings on various 10μF capacitors that seemed way too low. Checked again with the frequency at 100, and now getting readings much closer to the Keysight in the university lab. It seems so obvious, now that you have pointed it out, that readings for inductors and capacitors are frequency-dependent, but I sure missed that at first.
Just to be sure I'm not missing something else ... I'm guessing that readings for a resistor should not care about the frequency. Right? Or have I missed something else ... ?
Paul T:
It’s true, a pure resistor shouldn’t matter. However real resistors have inductance and capacitance. Especially wire wound. I use 1k for all resistors because the owners manual for my ztmd1 recommends best accuracy overall.
mawyatt:
Yes resistors are also frequency dependent and measurements should take this into account. They are also test level dependent as self heating can cause measurement issues (think TC).
Vishay and Caddock Resistors are the usual types folks look too for precision and stability. For capacitors the C0G/NP0 ceramic types are good choices, also Polystyrene and Mica but these are more difficult to find.
Getting highly repeatable results is difficult as everything from the usual ambient temperature and RH needs to be considered, but also the test signal level and type, DC Bias, test fixture, instrument measurement method, electrical environment & proximity and so on, influences results.
One also needs a thorough understanding of how the measurement instrument operates and computes the displayed parameters if expecting highly repeatable and accurate results.
As an example, a recent brief discussion concerning very high "Q" components and why the effective series loss element (Rs) was inconsistent in measurements, even displaying negative values!! These measurements were conducted on Lab Grade Bench LCR Meters. An analysis of the measurement method and parameter computation reveals an impedance magnitude and phase result from which the loss element Rs is computed. A high "Q" component will have an impedance phase approaching +-90 degrees from which the computation of element loss Rs is extremely sensitive to small angle variations, and can even produce the wrong sign!!
BTW we just received the MD1 and quite impressed considered the cost :-+
Anyway, these type measurements are well beyond what tweezers are intended for, but good for a user to understand.
@ awakephd Note you are working on your PhD, congrats :clap: What's your research area and university?
Best
DaneLaw:
--- Quote from: TheDefpom on September 25, 2024, 08:17:12 am ---I just recorded a review for the FNIRSI and found that I could not zero them, the manual states it can be done, but in my case is doesn't actually zero, but goes down to NEGATIVE mOhm's, from power up it does -38mOhm when shorted, if I put a 100mOhm resistor on it I get about 67mOhm... trying to zero gets WORSE, down to negative 66 or so, and then negative 102mOhm or so ! if I then put the 100mOhm on it, I get about 2mOhm !
Tried all different things, no good.
It's on V1.3, tried to install V1.5... firmware doesn't take, I get the disk on the computer, and have boot loader 0% on screen, but copying the firmware .bin over results in no change at all, nothing happens, again tried doing it different ways, no good, probably because I am on a Mac rather than a PC.
UPDATE tried on a PC and got firmware updated, didn't fix the zeroing issue though, that is no different.
--- End quote ---
Im not sure about the purpose of the "zeroing" that the manual explains..
On my unit (FW1.5) it almost looked like its adding a +10mOhm offset everytime...
so from reading around 3mOhm. and hold it together and push 5 times, it went up in the +50mOhm.
though one thing Im not fund of on the ST1 is the 1x screw fitting.. you need to clean the contact-surfaces and then screw it down, with more torque than you usually would do with a fingerscrew to get consistent reading, but in general the MD1 seems to perform better with low mOhm readings-.
awakephd:
--- Quote from: mawyatt on October 08, 2024, 01:47:02 pm ---@ awakephd Note you are working on your PhD, congrats :clap: What's your research area and university?
--- End quote ---
I apologize - I did not mean to be misleading! I actually earned my PhD 24 years ago, but in the humanities; I teach / serve as a Dean at Campbell University in central North Carolina. The university has a relatively new (~10 years old) School of Engineering, and I am finally getting a chance to fulfill a long-standing desire to sit in on a circuits class. Despite my professional focus on the humanities, I have been tinkering with designing / building circuits for 40+ years, and while I have generally succeeded in building something that works, I have always been painfully aware of how much I am "guessing" at design choices or at values to use (e.g., for a simple RC filter to quiet the bounce on a mechanical switch). Or as I often say, I have worked by trial and lots of error. :) Thus far, the class has been extremely enjoyable and has already filled in quite a few of the gaping holes in my knowledge. And this forum is adding to my knowledge as well!
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