ฝัง
- เผยแพร่เมื่อ 13 ต.ค. 2023
- In this episode Shahriar takes a look at an inexpensive power sensor module with built-in battery and a tiny LCD screen. The instrument claims a large dynamic range of -60dBm to +30dBm!
A leaky internal battery prevents the unit form powering on initially. After analysis of the chemical leakage (using an Agilent Resolve Raman) as well as repair of the battery, the unit return to normal operation. A detailed teardown of the sensor is presented along with the theory of operation for the front-end RF circuits and sub-components. The unit is then measured against a R&S 3-Diode Path NRP power sensor. Although it does not perform nearly as well, it can be used within +/-2dBm accuracy. The unit is then measured against its highest claimed frequency of operation and input power.
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With this video showing the accuracy and limitations of this little device, it actually makes it more useful. For under $100 being within a few dB this is actually quite a good value once you understand its limitations!
Would be nice to see the return loss of this device. I wonder if at high power there are a lot of reflections, a this was partly the reason the device survived.
Good question, the front-end attenuator is rated at 18dB return loss, for 9kHz-6GHz, so probably not reflections saving it (assuming small reflections from the connector and transition).
I did wonder about reflections impacting the other power sensor, but if they do it's below the error of the cheap sensor anyway.
Once again, great video!
I was going to ask the same thing!
Very impressive DEVICE considering that $85 is a tiny FRACTION of the cost of ANY of the other instruments appearing in this video. The cables alone are probably double or triple that.
The crazy thing is that you can get a breakout board with an SMA connector for the AD8317 for just over $5. If you're willing to use external attenuators, a DMM, and the table from the datasheet to convert the voltage into dBm, you'll get that performance for around $5.
Given 1.7% price ratio with the R&S, I would say this device from China knocked it out of the park. I wonder if they have a chemical analyzer version?
At lower frequencies this is useful for a ham radio experimenter, esp. those working at low powers.
The thing that immediately stood out to me was the inappropriate use of countersunk screws to mount the PCB in non-countersunk holes. I have noticed a lot of manufactures take a shortcut and use the same for the outer case. Plus the poor quality of the screws themselves.
Dodgy mounting is probably what killed the battery, too: I didn’t even know Li-ion cells could leak 😂
When you're trying to fry a piece of equipment on purpose, it will be as rugged as a brick, but when you're accidentally overload a few thousand dollar probe just a little - it blows! Murphy's law at full power!
Thank you for continuing to make this kind of excellent content year after year.
Great video! Very interesting to see what you are upgrading to when purchasing high end equipment from reputable suppliers.
Great and very useful video, as most of us can't afford the expensive equipment. In this way we can see the direct comparison to the high end professional devices. I hope more of this comparison will come. Like popular budget VNA's, spectrum analyzers, oscilloscopes, counters, power meters and such. I am a absolute newbie in RF and am setting up a hobby/edu Lab at home. At work we have some high end equipment I can do some comparison.
Thanks for the excellent video. For $85, a tiny fraction of anything from R&S or Keysight, this little power sensor isn’t too bad for a hobby grade device. As long as the user is mindful of applying appropriate attenuation, the results are good enough for amateur use. It is particularly nice to be able to have useable results at low frequencies.
I found that the offset value works, similar to other instruments with an offset type adjustment, for compensating "global error" and also performs the math for me when I have an external tap, say for 40db, and I hook my transmitter (5W), it will read out the actual value of the rf power.. Thanks for the video, I enjoy your tear downs and in-depth look at the underlying circuitry and its characteristics. Thanks for taking the time to do this, as well as eliminating superfluous "chit chat", your videos certainly respect my time invested, and show your extensive preparations... Thank you...
It would not have survived in my hands :).
We'll see about that. Since I was so genuinely impressed by it so I snatched one at 68USD shipped (with all the savings and everything). I hope they used genuine parts in my copy as well and I don't care if the battery is dead or not since I have a couple in my drawer.
This video sparked the above 1 GHz RF fever in me even more than your regular SA repairs. And I don't know if I (or my bank account) should thank you or not...
If they amend their claims a little, then it sure isn't a terrible part for 85 dollars.
10 GHz might be a bit too far of a claim, 6-8 GHz is more honest. Some software updates to make it able to say that the signal is compressed would also be good. As well as amending the text such that it takes attenuation into consideration when displaying power in db and watts.
Also curious to if it wouldn't have been better for them to skip the attenuator and instead just had some protection circuitry. Since shipping along an external 30 db attenuator isn't particularly hard.
It's typical for this stuff to have specs beyond reality, if it sounds a little too impressive divide by two and you'll usually be close enough.
@@Broken_Yugo I wouldn't say "specs beyond reality", since most of these manufactures of cheap test equipment often just goes with whatever they can squeeze out of the components and label the product accordingly.
It technically can measure power at 10 GHz, it just doesn't do it particularly accurate compared to how it fairs at more reasonable frequencies. Similar for power.
It apparently "can" measure 30 dbm, I thought it would fail here honestly, but my expectation were that it would take a few seconds, perhaps a minute. Though I can also see ambient temperature play a meaningful role here.
I have thus far not seen many cheap pieces of electronics test gear that makes claims beyond reality, but rather specifications that are based more on technicalities. I will though say that the claims by the manufacturers aren't honest, since technicalities is not what a buyer expects...
In the end, the claims made are far from what we see in other fields where a 300 lumen flashlight is sold as 80 thousand lumen. Or a 200 foot pound impact driver being marketed as 3000 foot pounds.
But yes, we should still be skeptical and point out these sorts of factual errors in claims, else electronics test gear manufactures will also stumble down into absurd performance claims.
Thank you Shahriar i really enjoy seeing budget devices performance measured with some accuracy
The proper way to use a splitter with unknown devices at its output is to use at least 6 dB attenuators between DUT and the splitter. Then the splitter (HP11693) will work relieably.
Great compound analyzers !
I can't tell you how happy I am to see you return to featuring something I could afford. $50,000 pieces of test equipment are cool but it's not that useful of a watch for me since I will never be affording that stuff. An $85 part, however, is in the realm of the possible.
Thanks very much for this fantastic tear down and analysis. I think the main thing wrong with this device is the exaggeration of its specifications. Without the attenuator in, it seems pretty decent from say 10 MHz to 3000 MHz and from say -50 dBm to 0 dBm with with the attenuator switched out. You get more range with the attenuator switched in, as long as you respect the ratings and specifications of tge attenuator.
Wow, did not expect that tiny power measurement chip to survive dissipating 30dBm. Suspect it got particularly hot though.
Thanks for evaluating this, power meters are incredibly expensive for the amateurs, so it's really helpful to know the real performance of these.
You noted the drop off at 9GHz vs 8GHz but didn't adjust the frequency setting. I'm really interested to know how hard they tried to compensate this drop off, do you know if theres some agreement if the frequency is adjusted?
This video provides the home-gamer with practical guidelines to a cheap power sensor. Very helpful!
Hello, I’d just like to say I love your content. I use to love computer architecture and digital design but I started delving into RF a year ago. Your videos are so great. I’m still a student and just got a co op in the RF field. I see all the test gear you showcase in your videos and I’m so excited to be able to use them for my co op. Keep making videos !
Interesting :) Now I want to buy one just to have a challenge of writing a better firmware :P
excellent video, great the survival test ! -- very impressiv, would be cool to see with a thermal imaging camera
Interesting to see at 22:15 when you add 10 dB of attenuation to the sensor, the power reading of the R&S sensor also changes by 0.1 dB. This suggests the S11 is significantly changing, which is also not interesting for a power sensor.
They actually let you keep that Agilent thing? That is cool.
I have bought and repaired many of things you see also.
he designed that thinf
Hi Shahriar, I have just taken delivery of one of these units. Fortunately its battery isn't leaking and it came fully charged! I have done a few initial tests using a signal generator and comparing it with an HP 8482A sensor and it's looking pretty good from 50-550 MHz at in input level of -10 dBm and no attenuation, as expected from the data sheet for the AD8317. Currently I'm puzzled about the pSemi digital step attenuator. You indicated a part number of PE43601MLI but that is a 6-bit device with a maximum attenuation of 15.75 dB. user-rw7md5mp7d suggested that it might be a PE43713. I have checked that. It is a 7-bit device with a maximum attenuation of 31.75 dB, as required, but its data sheet doesn't seem to match parts of the data sheet that you show in your video. (The same is true for the data sheet for the PE43601MLI.) I wasn't too worried about this, but now I'm frustrated because I haven't figured out how to open the case of the unit to look at it. Can you tell me how to do that?
I think you must have a newer unit like I have, with a small, power supply PCB visible under the plate and the rest entombed in the aluminum casing? It doesn't look like they want people to have easy access to the heart of the unit. Congrats on the good battery!
Yes, my unit has the additional PCB in the corner of the battery compartment. Its only function seems to be to support the ON/OFF switch. Presumably that has been added in these newer units to allow isolation of the battery during long periods of inactivity. It was switched off when the unit was delivered. I have left it on during the last week of occasional use, and I see the available capacity going down slowly between uses. The board also serves as a termination point for the battery wires, which is also useful. Meanwhile, I have figured out how to get inside the compartment containing the main circuit boards. It's evident in the video from about 4 minutes 10 seconds in. It seems that you have to peel the label off the front panel to remove the 4 screws holding it onto the box. They seem to be in-line with the 4 mounting holes (tapped M3) on the bottom (back) of the box. I'm not going there at this stage. I don't trust myself to do a pretty job of removing and replacing the label.
@@lewwhitbourn5813 Thanks for the reply. I have mine going now that I've soldered a new battery in. I don't plan to dig any further into the unit, but best of luck to you should you try.
@@item6931 Thanks for letting me know. You had bad luck with the battery. I'm not going to dig any further either, but I would still like to know the part number of the pSemi attenuator. I hope someone else may be able to tell me. I have looked at the data sheets of all the following, and none matches Table 3 or Table 6 or any of the Figures of the data sheet in the review: PE43601, PE43701, PE43711/12/13. I'm really puzzled by this!
Still better than measuring with a wet finger. And where can you buy the TSP?
Little chips that can survive. Perhaps response and errors could be also improved with user calibration, if there are methods provided by manufacturer on how to calibrate these.
I’m not an expert on all flavors of the ESP32, but I know EEPROM can be emulated using the on-board flash memory; not sure if there is a limit on the size. Using flash is non-ideal due to the limited number of writes, but for a calibration table which seldom if ever changes, that’s OK. With savvy programming, it ought to be possible to improve accuracy a lot. The problem is that doing the extensive calibration would take time and raise the cost of the device.
Thanks for the video, that agilent resolve must be intégred to our smartphone as GPS, gyroscope, thermal camera, and many other sensors.
Just looking at the package of detector a can sense ad8317. Attenuator probably pe43713. Nice videos as always!
Not bad for the home experimenter!
Not auto-detecting the best attenuation seems a bit strange, it is something that shouldn't even take an afternoon of programming to implement, seeing as all the functionality in the code is already there.
I recently bought one of these. Battery was DOA (no voltage across the terminals and would not recharge) so they may have systemic battery issues. Am waiting for a new battery I ordered - hopefully it will res the unit.
Really interesting on many levels, thanks! Design choices, shortcomings, performance. I doubt the instrument will last very long, and doubt even more there would be much customer service for repairs if it did fail. Nonetheless, like a NanoVNA it does give a pathway to learning and making some basic measurements at a low cost. It would be interesting to see the board under a thermal camera at high powers. The datasheet maximums are probably for continuous operation.
Data sheet maximums are normally "never exceed" values.
Other than the battery, which isnt really needed, what part is going to wear out?
@@stargazer7644 I agree, but they are possibly calculated on the basis of continuous operation at the highest allowable ambient temperature in this case. 1 watt of RF power is being dissipated somewhere, most likely as heat. It's not the same as a DC overcurrent case, but I think the thermal stresses will damage the chip eventually. Unless of course it's wildly underspec'd or Shahriar got a particularly robust one!
Wow, you are so good.
Is the "Power" line on this little unit off by a factor of 1000? I think I saw microwatts when he described milliwatts, and as far as I remember this was consistent.
But I don't know anything about RF or power meters.
Probably the same issue as the dBm readout: It just shows the value _after_ the internal attenuator (which is used to reduce the signal level so it can be measured properly).
Which doesn't make a lot of sense because the device could just calculate the actual value from the measured value and attenuator setting.
You could become the Photonicinduction of RF if you make an entire series where you make things pop.
Really liking the dark-mode data sheets. Does FoxIt do that?
No, I do it manually to save your eyes. :)
The NPR40SN uses its 3 diodes to be able to measure average power of modulated signals. Just for CW they wouldn't be needed.
Thank you for another interesting video. Is the USB communication link implemented or is it just a charging port? (Hard to tell by examining the video) Some off board software could easily be developed to correct most of the display shortcomings and allow for better calibration making this sensor very useful for hobbyists. Regards, David
The USB is only for charging.
@@Thesignalpath FYI, I just got one of these and under Win 10 OS, it installs a serial port and the V5 win program will read the power data around 10/sec. Pretty easy. Not sure yet how set the freq vs reading table. Seems way off on mine, but for any given frequency once set its accurate.
Funny coincidence... ATM, I'm designing a budget power sensor with fast ( target is
What would you need to measure rf power for ?? Broadcasting? Or wifi antenna testing? I had a power meter for optics but rarely used it over the optical time delay reflectometer.. but the radio stations and police ban radios used a few microwave antennas on top of a building i maintained. It had a double locked door to it because a custodian got killed smoking a cig by the satellite dish when they broadcasted.. i was up there once with a guy who configured the thing and stuck a hotdog on a stick by it then broadcast a test signal which completely cooked the hotdog and even blew the end open like when they cook in the microwave too long.. lol. Those cables are way bigger than the input on that tester..
what is the input VSWR ?
Thanks again
I'm guessing that the USB connection is for charging only ?
And not for external control or readout ?
Yes, charging only.
The unit I have uses the usb for a serial adapter. You have to load the driver, I asked the ebay seller for the link to the software, he sent it, and I have my USB connected to the computer running the software... My unit also has the manual on/off power switch..
Can you disclose the type number of the here used P-Semi and ADI parts? I'd like to study the data sheets.
PE43601MLI for the attenuator? AD8317 for the log amp. The second one can be seen on the PDF.
@@jaro6985 I am probably dumb - cannot find a PDF
@@ghlscitel6714 The PDF in his video that he is looking at the schematic. PE43602 you can search and the third link in google has a datasheet, micro semiconductor.
Attenuation of -10dB isn't that an amplification? This is a neat thing and if they had placed a temperature sensor close to the RF section and made the software open source, it would be a really nice thing that could be improved by the community.
I wonder if this is actually a design by a student or an individual, which was then copied wholesale by another business. The performance stats certainly have the feel of a Chinese business that ripped off a commercial design and then inflated the performance stats. Something in the style of that Atmel based component tester with LCD panel, or any number of small oscilloscopes.
How ideal of a load would this be? Is there any risk of a badly constructed power meter damaging the device under test by reflecting too much power or is that unlikely.
Put an external 10 dB attenuator between them if you're concerned about that.
that's a cool device the thing to determine chemical
Emeğinize sağlık efendim. Türkçe altyazılı da yayın yapabilir misiniz. Teşekkürler.Sağlıklı günler dilerim.
Not so bad, after all. It is perhaps unfair to compare the $85 power meter tot he R&S, since the R&S is free (i.e.$85 less, aka $0.00) At least that is all the information I could find on the internet. 😁
Was hoping to see that thing blow up
Just buy one and you can see it blow up first person! :)
This device would be kick-ass for the hobbyists, only if the software was written in a bit higher quality hid all the shortcomings of the hardware. No reason manual attenuator setting when the designers already know the linear range of the hardware and could have programmed this device to set it automatically.
Does the agilent device detect synthetic drugs?
Of course.
The tracking error of the splitter is not accounted for. I guess for this willy nilly power sensor it does not really matter. But for actual comparison between high performance power sensors it will.
The tracking error or losses of the splitter are not relevant here. We are doing a symmetric comparison between its two ports. A resistive splitter like this one has exceptionally well matched outputs.
@@Thesignalpath 0.25 dB (which is the spec for that splitter in the frequency range of interest) is not insignificant when comparing power standards with one another. As i said i agree that for your experiment it is good enough.
Yes, there is an uncertainty of 0.25dB, you are right. The VSWR of the cheap power meter also changes with the attenuation and that causes a shift.
I wonder how this device measures the frequency of the input signal.Thanks for the great video.
It doesn’t. It can’t.
Very interesting video. I think the criticism of the insertion loss of the attenuator and the calibration challenges that would add aren't entirely fair. Guestimating visually, it looks to me as though a bilinear fit to the graph shown in the video would provide +/- 0.2 dB residual errors from DC to 6 GHz and over a range of operating temperatures so wide it would be fatal to people in the same room. Of course those errors are added to all the other sources of errors in the device, but that one aspect of the design, at least, looks like a non-issue to me.
Other people have commented on the return loss. It looked to me as though the power being reported by the R&S sensor jumped a bit every time the attenuator in the demo device was adjusted.
This device can be relied at best +/- 2dB for any individual measurement.
Klingon blood flows in its veins....cheers.
3:57 that would be called a tricorder 🙂
But the industrial design of this is very bad, maybe the industrial designer was a toy designer before
For the price it is not even that bad. But I do not get why the manufacturer needs to lie about the numbers. They probably rely on the customers not having the equipment to verify them
Then why not 20 ghz? I suspect the equipment they tested it with was dodgy! The manufacturer may be completely honest but a bit unqualified.
I like that it does not correct the displayed result for attenuation.
The cellulose is just the cotton of the swab itself.
Yes that is what he said.
It sounded like he said that microcrystalline cellulose is used in cosmetics and thats whats in the swab, its just regular cellulose that happened to have a spectral match with the microcrystalline cellulose in the library based on the Raman they are the same@@-vermin-
-9001 dBm to + 9001 dBFS / dBi + dBV
So many 1/10th bells.