EEVblog 1557 - Micsig SigOFIT Optical Fibre Probe + GaN Experiment
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- Опубликовано: 6 июл 2024
- Review of the new Micsig SigOFIT Optical Fibre oscilloscope probe, including a practical demonstation of the incredible CMRR range of opticallly isolated probing of a 300V GaN transistor driver circuit.
And a direct comparison with the HVP-70 high voltage differential probe to show you the incredible game changing difference optical fibre probes make.
www.micsig.com/SigOFIT/
CMRR Explained video: • EEVblog 1521 - Common ...
Forum: www.eevblog.com/forum/blog/ee...
Links:
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
www.infineon.com/dgdl/Infineo...
Demo board: www.digikey.com/en/products/d...
00:00 - Micsig SigOFIT Optical Fibre Probe vs Active FET
02:25 - High Voltage Differential Limitation and why you might need an Optical Fibre probe
03:25 - Galvanically isolated, and power-over-fibre
04:39 - Comparison with the Tek IsoVu & Lecroy DL-ISO
05:55 - The CMRR is AMAZING!
07:15 - A look at the SigOFIT probe
10:04 - An optical fibre probe is NOT a high voltage differential probe!
10:40 - Practical example using a 600V Gallium Nitride GaN circuit demo
11:39 - What is a Gallium Nitride (GaN) Transistor?
13:23 - GaN / HEMT, and Silicon Carbide SiC Transistors
14:21 - IGOT60R070D1 600V GaN datasheet & Half Bridge switching configuration
15:30 - This is IMPOSSIBLE with a regular probe!
19:07 - GaN EiceDRIVER chip
19:54 - The practical GaN test setup
23:10 - Remote MXO4 scope control to take measurements
24:36 - High side GaN power transistor measurement with the SigOFIT
26:26 - Here is where the CMRR MAGIC happens!
27:41 - Comparison with HVP-70 High Voltage Differential Probe
28:45 - Look how the High Voltage Differential Probe is just horrible here!
31:56 - Baseline High Voltage Differential probe ringing vs SigOFIT
32:21 - Noise measurement
36:27 - Conclusion
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Thank you so much for making this great review, Dave. Really appreciated!
Take it there are a lot being sold in Switzerland, to a certain large company that needs to get the best results out of the small signals they get on detectors, that ride on a large circulating current.
Dear @MicsigOscilloscope please finally allow us to unlock your SATO scope series.
Why cannot you use usual 4 channel oscilloscope connecting 1, 3 channels to the high drive points and 2 and 4 channels to common ground, then use math functions to get differentials between 1 and 2, the 3 and 4, then math again to measure differential between the so maths effectively ibainjng ideal waveform? Save tons of bucks!
Don't turn it on, take it apart!! :D
Hi Dave, at 27:50 of this video you seems to get mad because you accidentally pressed the Preset button and your settings were gone. Since you are using a Rohde&Schwarz oscilloscope, actually this would have not been a problem. Indeed, in an MXO4 you could have just pressed the "Undo" button in the Toolbar (available among the settings of the upper left corner ) to get your settings back. Since the Toolbar is customizable, I would suggest to have the Undo button among the favorite ones.
PMK makes another option for optically isolated probes. They were some of the original designers of the Tek IsoView before they went off to do their own things. Generic coupling, up to 1.5GHz bandwidth, battery powered with an 18650 cell, nifty offering.
I've never needed to be so well informed about such a usage case - but I really enjoyed learning through this example. Top effort Dave!
I was involved in helping design a fiber isolated probe for an industrial system and its crazy hard to get good linearity and long term stability, we tried many systems including PWM/Class-D style, biased LED analog, laser power level stuff, in the end we just isolated the entire data converter
granted it was for a 16 bit system and none of us specialized in this but still i have massive respect for the engineers who even went as far as fiber power
hmm how were you transferring the data? like digitally whats the linearity problem with it? analog sure it would be really problematic(that's how powerglove works iirc, or some other glove anyway).
you can now get optical 50 feet thunderbolt cables off the shelf, so stuff related to it has probably gone down a lot in cost.
Just found this video thanks to your livestream. I am finding so many channels I've been subscribed and set up alerts for that are not showing up when I browse. YT is so frustrating. My dad was an electronics technician and your channel truly helps me deal with his recent health incident that has him unable to do what he loved. Please keep the faith my friend. So many of us love what you do, even if it isn't reflected in the YT stats.
A similarly good option for these high common mode signals is the "CleverScope". It has similar CMRR in a traditional design. A small company, but the product is very impressive!
Fantastic review, this is the kind of videos we love the most. So much information I need to watch 3 times
Would be interesting to compare this setup with the Cleverscope CS548 (discussed in EEVBlog #1119). From my understanding it has 100dB CMRR at 50Mhz and 4 isolated channel with 200MHz bandwidth. They also have remote digitizes for multi-KV isolation. And the price is quite comparable.
At 25:48 you talk about what you call "ringing" on the rising edge of gate voltage. That's not due to the probe connection, but it is the Miller Plateau effect of the MOSFET. The change of direction of the gate voltage is due to the low (or missing) gate resistance between driver and gate; with higher resistance, that shape would change to a short flat line (then the term "plateau").
This happens because the gate voltage is pulled down by the GD capacitance initially charged to rail voltage and then suddenly connected to ground by the turning on of the MOSFET. Once discharged by the gate driver, the GD capacitance will appare in parallel to the GS capacitance, and the gate voltage will start to rise again.
The effect is visible even at turning off (with opposite polarity). The lower amplitude in this case shows the different source impedance of the driver in the two states on and off.
This is fascinating. Thanks for doing this demo!
Nice demo Dave.
Enjoyed the video Dave, thank you!
Awesome video. Love the enthusiasm!
What a doozy! Dave got so excited - now I wanna measure something myself. 👌
Great probe.
Great review! Stocked in USA at Saelig!
You could still measure the high side switch on the cheap by using battery powered portable oscilloscope. This was done for the decades. The only scenario when you'd need this probe is when you have few signals to observe and they are synchronous so timing is critical .
CMRR of battery scope is also very bad. A key element of these optical probes is the tips: they don't use off-the-shelf coax, and include "distributed common-mode chokes" along their length. It's not possible to achieve the same thing with battery scope + passive probe + clip-on choke.
I know this because I've tried it - battery-powered scope vs IsoVu with a common-mode signal with over 100 V/ns slew rate and there's just no comparison - battery scope gives you garbage, IsoVu gives you something intelligible.
Excellent video. 🤓👍
Don’t forget to deskew your probes! Optical probes have appreciable propagation delay.
The label is upside down for the Australian market, of course.
This is excellent. 😍
I hope you were using a bigclive approved explosion proof container.😂 Really enjoy the technical talks on the various subjects you've presented. Keep up the good work. Sean from Canada.
Dave approved.
good enough for 'straya!
@@EEVblog Going to catch the chunks, but still allow the audio and visual failure to operate, plus still allow the magic smoke out safely.
Very good
Not only physics and R&D, but also a more or less forgotten group, repair. And then the more advanced repairs on component level. Things like big HV SMPS, HV calibration gear, Capacitor banks chargers (Had to repair a 6kV one, blew up a Brymen BM869S DMM when the thing spit out >40kV where only 500V should be) or f.i. a laser RF, they are almost impossible to probe. I use a diff probe (On a R&S 300 MHz full options RTB2004 (best scope I ever used) all the time because while trouble shooting I do not only measure against ground. It is much faster to probe around with a diff probe while troubleshooting (Most times without schematics so a lot more probing) I will buy one, thanks for the demo
Are you done making new videos? Such a shame!
@@worroSfOretsevraH, I'm sorry, It just costs to much time and I hate editting.
Nearly a million subscribers 🤞
At current growth rate, it'll take another year or two.
It would be nice to see a signal taken from the low side of the bridge by a passive 10x probe for comparaison (especially since that is what I would do if I had the problem - just measure the side you can and then assume that they must all work the same).
And of course it would be a pleasure to see a teardown of the power transmittion optics and electronics of the thing (especially on the receiving side).
But other than that it is a great video!
The low side is just a regular probe measurement, no CMRR switching, nothing interesting there at all.
@@EEVblog It would just serve as a phase shifted reference to compare the more interesting signal to. It would show how a signal from a near perfect differential probe should look like assuming all the transistors and driver circuits are near identical. And the more similar the signals would look the better the differential probe must have been in order to produce the result.
It is a minor thing of course, the situation with the fancy probes is already clear as it is. I was just surprized to see the fourth channel of the scope unused :).
love the plastic containers
Mrs EEVblog OH&S approved.
Now I know how Hypex amplifiers get their efficiency, I was hairscratching when I read the datasheets. These are class A amps from 2x35w RMS in 2R, they are all modular, great for DIY. But with the lack of measurement tools, like yours, that is not gonna happen. Great video.
Hi Dave, you have another couple of subscribers. Me and the boyfriend LOVE your vids and the Ausie frankness of speech. Keep up the good work Dave.
Wayne & Nina (Pom bastards ) 😃😃😃🇦🇺🇦🇺
❤️❤️❤️❤️❤️❤️❤️❤️👍👍👍👍👍👍
If I recall the highest bandwidth scope Micsig have in their line atm is 500Mhz and that is still mainly CN market that ETO been released, for western market it peaks at 300Mhz if I recall with TO series-.
but think twice before you jump into bed with that company.
they will promise a lot, to create hype & goodwill, and then not deliver and instead hurry into hiding, like Micsig own rep on EEVblog did.
The way the threated their 1000C series buyers, was a joke with their running app-ecosystem that would get constant new apps and features etc and the nail in th coffein was the latest faulty OTA update that crumbled the bandwith filtering, that otherwise was one of the really good thing, until they broke it with one of their infamous OTA updates.
I have not heard this, link?
Very cool
I'd love to see how they send 'power' over the optic fiber?
Just dump a few watts into the laser diode and hope you get enough out the other end after conversion.
I've yet to get a real oscilloscope to experiment with...being a mechanic by trade I've used pocket or built in oscilloscopes to see starter current to judge compression, coil pack current to check them or trigger to watch crankshaft position, camshaft position sensors to catch intermittent or weird failures, etcetera. But I need a real one so I can dive headfirst down the rabbit hole and really level up my diagnostic abilities...I know the theory but have not been able to put it to use...and oh my...the ability to see what is actually happening on any data line...save me alot of time...instead of guessing if an ecm is getting or providing data etc...yes please...GaN is something I'm looking forward to for power supply...ive noticed chargers for example output less once at it working temperature...2 amps cold and 1.4 hot on a phone charger...I throw them away
@@bentboybbzwhere do you live?
@@EEVblog Lets see it then. Don't turn it... Tear it apart!
The changlle of the test is , the GaN Components has fast slew rate which rise time can up to 1ns,the traditional device can also have MHz switch speed, but the traditional differential probe can take a measure.
A teardown would be super cool, especially the probe head with the fiber-optic power.
Because you would need to convert the incoming powerful laser light to power the circuit, and then still have enough juice left to send another laser signal back, all with up to 1GHz of bandwidth? Some interesting power envelope calculations for sure.
interesting bit of gear ill never touch! :P
...for me, i wouldnt be happy with that box hanging out the front of a scope...it would be nice if it had a small pigtail on that end to take all stress off the scopes connector
Hi Dave, thanks for the demo, it's amazing what technology can do 🤔 if I don't eat, drink or pay anything for a year and a quarter, I could buy one 🤣
Nice day 🙂Tom
Saker in Spain makes one. It uses a battery instead of a high power laser to power the isolated head.
Interesting. 6084€ and you don't get ower over fibre which is nicer. But can be used with any scope. It stops at 220MHz though.
In the field I'm working at we have to measure signals up to 500MHz up to 800V that are earth reference.
Unfortunately that optical probes are the only ones that are suitable for that. I talked with a Tektronix representative and we decided not to buy that probes ... it's just too expensive; we would need 6 of them. 😢
Hi, you can send us your request. 😊
The signal over the fibre optic cable is definitely modulated. I believe it's frequency modulated, at least the Teledyne LeCroy one anyway.
The logo is the right way up.
It's so that when the case is open you can flex on your colleagues like with a macbook
Going to jump on the "take it apart" bandwagon. Are they using off the shelf optics? Assuming two fibers, one for power, one for signal, but idk they could be using a single fiber and muxing two wavelengths on it.
Wow! What I wouldn't give for one of those bad boys. I need to try and slip one onto a big purchase order - hopefully nobody will notice :)
Great video, I would love to see a comparision between SigOFIT, IsoVU and DL-ISO in the future, I would also like to se how they compare on the low side vs a passiv probe. I did a test 4 years ago on the isovu on both highside and lowside, and on the lowside the isoVu seemed to have faulty noticable lower voltage level after the rise time, it was a demo probe so it may have been damaged. Anyway it would be intresting to see.
no teardown?bakayaru!
When we gonna see an eevblog version? 😁
Hi Dave, what if using an Isolated Scope like the older Textronix THS720x Series ?
All 3 channels are fully Isolated against each other and against the Power of the Scope itself.
It would be interesting if you try to measure the same high side FET's gate with cheap portable battery-powered scope like Fnirsi DPOX-180H which you reviewed recently for comparison.
How do you send power using fiber optics? I'm only a few min into the video so not sure if this is covered, will find out though. Really want to know though!
Does anyone know what type of sensor maintains the distance between an EDM electrode and the workpiece to prevent short circuits? Great fan. Thanks
I wish you have tried the comparison at 10khz and 100khz , since these frequencies are more common for Si mosfets . Its intresting to see if HVP is sufficient
Do you use LISN when measuring conducted EMI?
PMK and Saker are other low(er) cost alternatives.
So where do i buy ready made modules like step ups and buck converters that use GaN?
Could this be used for surge test? 1.2/50 uS testing to see what your surge clamping actually does. That is 6kV across the differencial. Question from a young engineer so please let me know if there is a way better way.
Not 6kV, that too high for these class of probes.
Dave can you compare the CleverScope to this one ? Also to the SAKE isoVP? Additionally, the GaN board you chose is one particularly slow compared to other FETS available there. Maybe Gansystems or EPC high voltage gan ?
With GaN/SiC, it's not just the switching frequency that you need to worry about, but also the frequency content of the switching edges themselves. When you were using the "traditional" HV probe and you reduced the switching frequency of the converter, things only "looked nice" because of the time scale required to show a full switching cycle. if you had zoomed-in to the switching edges, it still would have looked horrible, with ugly ringing all over the place.
Hi. Any updates on the alkaline battery leakage test started three years ago?
GaN sounds familiar, and that fly-in at 38:11 makes me wonder if this is the same chemistry used in blue LEDs?
Dumb Question: Assuming you could find an USB Scope with isolated trigger, wouldn't it be easier to isolated the USB interface as well? Use two scopes, and let the isolated trigger sync the waveforms between channels?
I know it's not but I really want to call this an "Optocoupler on a stick"
Close enough
Just wondering if an old analog scopes with differential mode (or does any modern scope still do this in signal level?) can measure such high-side drive.
And who when will be that "take it apart! " part?
Modern digital scopes can do the same thing using math functions. Best case I think the results mirror those of the traditional HVDC probe.
Didn't Dr TSP do a video on this type of probe a few weeks ago
Oh boy. This one is going to be a “didn’t watch enough of the video before posting” test for some folks.
LOL, yeah, I just added time markers.
Rather than powering the head via a laser why not just put an couple of AA batteries in the head? Apart from the convenience isn’t this a rather pricey way to power it? Is there any other advantage?
How is power sent to the probe end over optical? Does the probe end have some sort of solar cell to convert light to electricity? Thx
Photodiode.
Couldn't you get pretty much the same result by measuring the high side gate drive wrt 0v, measuring the source voltage wrt 0v, and subtracting it from the first signal to get the gate drive wrt the source voltage?
I guess when switching at 1kHz you didnt see any ringing in your diff probe because you zoomed out 1000x from your 1MHz reference measurement. The switching frequency isnt actually important for the CMRR but the slope of your switching events. In this case a great CMRR at 1MHz wouldnt help much if it is bad at 10MHz or higher.. Great video though, thanks :)
"Power over optical fiber"? I don't know SQUAT. Just saying. Thank you for the 1st class SchOOLing.. Can't wait for these units to hit the used eBay market.. I expect them to have their cables wound up tighter than "speaker wire". Just like they do with the irreplaceable TEK & HP probes :O\ Sweet demo! p.s. COoL-GaN_Galium_Nitride is my new go-to geek speak. Yeah baby!
They could have just robbed you, but they insist to offer you a probe
Since I didn't quite get it and this is far outside my area of expertise, are there actually probe tips to this or are you supposed to design smx connectors onto your board to use these probes? I guess the use case is not so much for probing but testpoints? I doubt I will ever see one of these in the "wild", but nonetheless, very interesting piece of kit.
You can just solder on a short coax like I did. But it's not uncommon to design PCB's with dedicated test points in mind, especially where it's critical.
@@EEVblogThanks for the reply. I guess that makes sense, especially given how these go up to tens of kV. How would they go about designing the test points for the full 60kV though? Wouldn't that arc 2-3 cm in air? I don't think I've ever seen an MCX connector with such a rating and in the manual the 2000:1 tip still looks like it uses those.
*notices the stand*
So audiophiles are right to put their cables on standoffs?
My manager still don't get it why cmrr matters . He sees only $ .
22:18 It goes to 11!
You turned it on, and didn't take it apart? Are you feeling okay?
How can we send power over fiber i mean power with light how 🧐
take 2 ferrite rings, wind 10 turns + a 50 ohm resistor and that's it, the price is $ 1....and saving $3,000))
I’m not sure if it’s as easy as you said.
Getting a transformer to have a flat frequency response from near DC to 1 GHz does not sound trivial.
Ah yes the optical probes to measure the light frequency
How does it transmit power then?
Light in the other direction than the signal.
Just stick a handful of whatts into the laser diode and hope you get enough out the other end after conversion.
Dave, your 1kHz test is nonsense. Just increase the time resolution and see that the edge is as bad as with 1MHz. Rise time of the halfe bridge does not change with clock frequency!
Yeah, but the point is that you don't care about that edge nearly as much in terms of energy and gate drive losses because of the time/vs duty cycle then you do at 1MHz.
@@EEVblog say what? You dont care about the signal integrity of the gate driver? Cmon!
@@EEVblog Looks like you are too long out of the engineering business and too long into the show business. What could go wrong when a half bridge gate drive switches bad . . . If you don't see a problem, it's not there, isn't it?
@@JacquesMartini No why would you care at 1MHz, thats super slow switching speed.
There goes dave with his old man comments. Dave the label is not upside down. When your carrying it by the handle the label is correct.
Really schmick. I want to experiment with GaN stuff but when the cheapest one is more than 2x the cost of the most expensive equipment in my lab, I think I will just connect a scope to a battery and use a normal probe.
@@MonkeySci I have thought about that. I am thinking to get a good response would require custom filters and a lot of tweaking on a VNA, but it seems doable. Not as bad as making a DIY normal probe, right? No unobtanium lossy coax 😄
@EEVblog "Don't turn it on, take it apart!" What gives?
garloid
Why cannot you use usual 4 channel oscilloscope connecting 1, 3 channels to the high drive points and 2 and 4 channels to common ground, then use math functions to get differentials between 1 and 2, the 3 and 4, then math again to measure differential between the so maths effectively ibainjng ideal waveform? Save tons of bucks!
........did you say POWER over fibre?????? is this a mistake or am i going to be blown away if i watch 33 more minutes?
Yes, pump a few watts of light into the fibre and it comes out the other end.
I have a... strange question. You used the term: Totem pole. I was thinking what that meat in Australia, but then I realized those objects are part of the indigenous North American-North West culture.
And now I'm scratching my head, wondering about how Todem Pole output is a meaningful term. I think you mean Push-Pull, which may have been nicknamed Totem Pole at some point in history, but it has nothing to do with those objects at all.
Totem Pole is common industry term for this arrangement. Or Push-Pull, Half-bridge, take your pick.