So if you look up the AP Instruments Model 102B Manual (I found one here: http://www.apinstruments.com/files/102Bman.pdf), Page 54 (PDF numbering) / 50 (document numbering) shows your typical FRA setup used. The VNA calculates the frequency response from the ratio of its inputs Channel A and Channel B. So the Source impedance and transformer phase / amplitude cancels out from the equation. No calibration required, just a good matching between Channel A and B (which one expects from a decent VNA).
Within limits of course, since one needs a minimum amplitude of source signal coupled through the transformer to get a useful signal above the noise floor.
QuoteHow did you calibrate?
Huh? You want me to explain the 102B's cal procedure?
@rx8pilot,
Thanks for sharing your approach to learning this stuff. You can look at all the various equipment user’s manuals, they don’t take much space to explain the interworking of stuff. The best single source I can recommend today is “Power Integrity”, Measuring, Optimizing, and Troubleshooting Power Related Parameters in Electronics Systems by Steven M. Sandler.
rx8pilot:
For building up some confidence in the cal and measurements procedures, I'd recommend to rebuild the HP35676A test set:
http://hparchive.com/Manuals/HP-35676-SCHEMATIC.pdf
No need for all the fancy metalwork, and don't worry about the unknown capacitor, it still works built on a piece of SMT protoboard using some MiniMelf resistors (some of the series connected to get near the original value).
Once calibrated using the full cal procedure (again, no need for a fancy cal standards set, a wire and a 50 Ohm resistor works, you'll get some ripple at the 200MHz end), then switching the 3577A to impedance display (choose "F4" as the input to display , it's written somewhere in the manual), you can get impedance sweeps of known components (start with resistors in the 10 Ohm to k Ohm range) and get familiar with the way it works. Measure some inductors and capacitors, read the imaginary part at some frequencies and do the math to verify your reading. Inductors are quite fancy regarding their impedance over frequency, many of them are inductors at rather low frequencies only.
There's also somewhere a manual on the net (for this or the HP35677 test set) that has a better description of how to measure impedance using the 3577A than the 3577A manual.
Edit: Found it, here it is: https://cb.wunderkis.de/wk-pub/Keysight%2035676A%20Data%20Sheet.pdf
Edit 2: Don't know what you mean by "skewed", the manual has some tips regarding the RBW setting: Reverse the sweep direction and watch if the graph shifts. If it does, your sweep speed is to fast for the chosen RBW.
Edit 3: "F4" is impedance for a 50 Ohm system and calibration, "F5" is for 75 Ohm
rx8pilot,
It is easy to make a mistake. I suggest that you check all the connections with a volt meter to confirm that the voltages are safe for your expensive test equipment. It is easy to vent the magic smoke.
Thanks DT
I know the question sounds fundamental - and it is. This is a topic that I am new to and I have very little confidence in the results I am getting. I have been trying to better understand the network analyzer (in a general sense, not model specific), inductor measurements and analysis, and frequency response analysis of SMPS control loops. One of the things I am trying to figure out is essentially a 'sanity check' to make sure the results I am getting are reasonably accurate.
Perhaps gathering the manuals for the AP VNA, Bode100, E5061-LF, etc would help me gain some confidence in how I am going about the process. Repeating some of the measurements in this thread should also help since I have the Jensen ISO-MAX VB-1BB that has been measured by a couple of people (comparison)
Does anyone know if the Bode 100 has AC coupled inputs? It did not look like it after scanning the brochure.
Perhaps gathering the manuals for the AP VNA, Bode100, E5061-LF, etc would help me gain some confidence in how I am going about the process. Repeating some of the measurements in this thread should also help since I have the Jensen ISO-MAX VB-1BB that has been measured by a couple of people (comparison)
I wonder why Dave was so impressed by this transformer.
It's a heck of a lot better than some DIY ones I've used.
I was wondering what is so special with the Omicron B-WIT100 from your teardown transformer, and I was able to duplicate the transfer characteristics using two stacked cores from Vacuumschmelze (VA), PN T60006-L2030-W514. The result are almost identical (all was measured on a Keysight E5061B-3L5 in now have on a test loan).
The big difference is the cost: My transformer is about 60 to 70€ including the box, the Omicron is about 500€ incl. VAT.
All the nittigritti is documented here (at the bottom):
https://electronicprojectsforfun.wordpress.com/injection-transformers/
All the nittigritti is documented here (at the bottom):
https://electronicprojectsforfun.wordpress.com/injection-transformers/
Do you want the STL for the holder ?
Do you want the STL for the holder ?
For sure, I don't have a 3D printer but I can CNC machine it from Delrin.
I will probably machine a case for it and give it a fun name: NVT-1
Nude Virgin Transformer - 1