https://community.element14.com/technologies/test-and-measurement/The electronic test and measurement group is intended to prove information on electronic test and measurement equipment, including thermal imaging technology, and also answer any questions you may have.en-USTelligent Community 12https://community.element14.com/technologies/test-and-measurement/b/blog/posts/nordic-power-profiler-kit-iiSun, 11 Oct 2026 12:14:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:4e9e957e-5a8c-45b5-b3ee-8b8698a08232kk99Introduction I have decided to try one of the devices used for power profiling and power optimization of embedded devices. Among the devices available at a similar price point, I have narrowed my choice down to two options: the Nordic Power Profiler Kit II and the STLINK-V3PWR. The table below provides a brief comparison of these two devices: Aspects Nordic Power Profiler Kit II STLINK-V3PWR Measurement type source measure or ampere meter source measure Measurement range 200 nA - 1 A 100 nA - 550 mA Measurement accuracy 20 % (avg. current) 2 % Voltage output range 0.8 V - 5 V, up to 1 A 1.6 V - 3.6 V, up to 550 mA Measurement bandwidth not specified 50 kHz Sampling rate 100 kS/s 100 kS/s Power input 2xUSB, one is power only USB Debug probe no yes Extra features 8 channels logic analyzer bridges USB to SPI/I2C/CAN/GPIO Price at 2026 at Farnell £87.564 inc VAT £143.844 inc VAT Since I already own debugging probes such as the STM32 ST-LINK and J-Link EDU Mini, and the PPK2 offers additional features, including an ammeter and a logic analyzer, as well as a wider voltage range, I decided to purchase the Nordic Power Profiler Kit II, despite its lower measurement accuracy. I ordered it from Mouser, and the device arrived very quickly without any issues. The box contained: one Nordic Power Profiler Kit II device four dupont cables for power connections ten dupont cables for the logic analyzer Here is a photo of the complete set: Setup The setup is simple: you only need to connect the device to a computer using a USB cable. In this configuration, the device can deliver up to 500 mA. To supply up to 1 A, a second USB cable must be connected. The PPK2 is managed through the nRF Connect for Desktop framework by running the Power Profiler app. nRF Connect for Desktop is available for Windows, macOS, and Linux. For Linux, it is distributed as an AppImage, so no additional dependencies need to be installed. However, on Linux, one additional step is required: installing the udev rules provided by Nordic Semiconductor, available here: https://github.com/NordicSemiconductor/nrf-udev . These rules can be installed using the nrf-udev_1.0.1-all.deb package or by adding them manually. Without these rules, the device will not be detected by the Power Profiler app, and the following error will be displayed: Measurement The Power Profiler app is intuitive and easy to use, allowing you to get started quickly. For my first test, I decided to evaluate the SMU mode using the following precision resistors: - 15 ohm 0.1 % - 150 ohm 0.1 % - 1.1 kohm 0.1 % - 10 kohm 0.1 % - 1 Mohm 0.1 % As a first step, I measured these resistors ( R_mes ) using the four-wire measurement method with an HP 3468A multimeter. The measurement results are presented below: {gallery}Resistors measurement 15 ohm 0.1 % 150 ohm 0.1 % 1.1 kohm 0.1 % 10 kohm 0.1 % 1 Mohm 0.1 % Using this information, I measured the voltage drop (V_r) across each resistor during the Power Profiler Kit II measurements with the HP 3468A. I then calculated the current (I_r) based on these voltage measurements and used it as a reference to determine the absolute error ( δ% ). I decided to use the 1-3 V range to keep the HP 3468A's input resistance at approximately 10^10 ohm, minimizing its impact on the measurement circuit. Using the Power Profiler Kit II, I measured the average current (I_avg) over a 10-second interval. A photo of the measurement setup is shown below: The tables below present the measurement results for each resistor: R_nom [ohm] R_mes [ohm] V_set [V] V_r [V] I_avg [mA] I_r [mA] δ [%] 15 14,997 1 0,95487 62,48 63,67 -1,87 15 14,997 1,5 1,45175 94,58 96,80 -2,30 15 14,997 2 1,94983 126,53 130,01 -2,68 15 14,997 2,5 2,4353 157,6 162,39 -2,95 15 14,997 3 2,9212 189,66 194,79 -2,63 R_nom [ohm] R_mes [ohm] V_set [V] V_r [V] I_avg [mA] I_r [mA] δ [%] 150 149,973 1 0,9646 6,42 6,43 -0,18 150 149,973 1,5 1,46401 9,52 9,76 -2,48 150 149,973 2 1,9447 12,59 12,97 -2,91 150 149,973 2,5 2,45162 15,87 16,35 -2,92 150 149,973 3 2,93926 19,12 19,60 -2,44 R_nom [ohm] R_mes [ohm] V_set [V] V_r [V] I_avg [mA] I_r [mA] δ [%] 1100 1099,82 1 0,96535 0,95422 0,88 8,71 1100 1099,82 1,5 1,44416 1,38 1,31 5,10 1100 1099,82 2 1,94401 1,82 1,77 2,97 1100 1099,82 2,5 2,43255 2,26 2,21 2,18 1100 1099,82 3 2,93672 2,73 2,67 2,24 R_nom [ohm] R_mes [ohm] V_set [V] V_r [V] I_avg [uA] I_r [uA] δ [%] 10000 10005,1 1 0,90225 90,38 90,18 0,22 10000 10005,1 1,5 1,44571 143,36 144,50 -0,79 10000 10005,1 2 1,94507 192,56 194,41 -0,95 10000 10005,1 2,5 2,4332 241,41 243,20 -0,73 10000 10005,1 3 2,91996 291,01 291,85 -0,29 R_nom [ohm] R_mes [ohm] V_set [V] V_r [V] I_avg [uA[ I_r [uA] δ [%] 1000000 1000890 1 0,95756 0,89 0,96 -6,97 1000000 1000890 1,5 1,46158 1,44 1,46 -1,39 1000000 1000890 2 1,96516 1,98 1,96 0,84 1000000 1000890 2,5 2,45742 2,49 2,46 1,42 1000000 1000890 3 2,94845 3 2,95 1,84 Summary Based on these measurements, the accuracy appears to be quite good, especially considering the specifications provided by the manufacturer. However, one factor may have influenced the results: the PPK2 measures the average current over a 10-second interval, whereas I used a single voltage reading from the HP 3468A to calculate the current rather than the average voltage over the same 10-second interval. I may revisit these measurements once I have built the HP-IL interface. The largest error, however, appears to occur near the range-switching threshold. Nevertheless, it remains within the manufacturer's specified limits. The Power Profiler app also provides an advanced menu that allows the gain to be adjusted for certain ranges, which may help reduce this error. Overall, it is a very capable device that allows you to estimate power consumption and profile current usage. The built-in logic analyzer is also useful when correlating GPIO signals with power consumption.nordic ppk2nordicpower_analysissmupower profilinghttps://community.element14.com/technologies/test-and-measurement/b/blog/posts/researchers-observe-altermagnetism-in-layered-materialFri, 09 Oct 2026 08:00:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a0d5b71d-5222-4a9c-9557-879d25c3275aCatwellThe lab has molecular beam epitaxy (MBE), angle-resolved photoemission spectroscopy (ARPES), and time-resolved ARPES systems. (Image Credit: UCF ) Researchers are looking for new techniques to achieve faster computing. To do this, they are focusing on spin rather than the electrical charge of electrons. Physicists at the University of Central Florida (UCF) have recently experimentally observed altermagnetism in a layered material. This revealed spin-split electronic states that occur regardless of the material having no net magnetization. The Co 1 / 4 TaSe 3 material is made of cobalt atoms intercalated between tantalum diselenide layers. This crystal has a hexagonal structure, and the cobalt doubles the in-plane unit cell. Magnetic susceptibility measurements revealed the material is antiferromagnetically ordered below a Néel temperature of 178 K. With this Type-A antiferromagnetic configuration, the cobalt moments match ferromagnetically within a layer but have opposing orientations in adjacent layers. This generates zero net magnetization. Single crystals were grown by the team using chemical vapor transport. To produce a precursor, cobalt, tantalum, and selenium powders were sealed in an evacuated silica ampoule and heated at 1,742°F for five days. Afterward, the material was pulverized and annealed for another five days. They then combined that powder with iodine before being sealed under vacuum and heated It at 1,724°F for two weeks. This process produced flat, plate-like single crystals. Angle-resolved photoemission spectroscopy (ARPES) was used by the team to examine the electronic structure. They cleaved the crystals at 7 K under an ultrahigh vacuum. This exposed a fresh surface for measurements. ARPES used 55-eV photons to map the electrons’ energy and momentum. Various photon energy measurements allowed the team to probe different positions along the material’s out-of-plane momentum direction. Measurements showed a six-fold (g-wave) spin-splitting pattern. Splitting became more evident along a specific direction in the material’s momentum space. It went away along symmetry-protected directions where the electronic states were still spin-degenerate. Momentum-distribution curve analysis discovered two peaks separated by 0.09 Å -1 , close to the instrument’s resolution of 0.08 Å -1 . The team used spin-resolved ARPES at the Advanced Light Source to examine the bands’ spin character. Across the electronic band, the spin polarization changed from -13% to +13%, which means the dominant spin character reversed as the team moved through momentum space. This revealed that the splitting was associated with the altermagnetic spin texture predicted by density functional theory calculations. Temperature-dependent ARPES proved that the electronic structure was connected to magnetic ordering. 7 K and 200 K measurements revealed that the Fermi surface and valence-band structure changed as the material was heated through the 178-K Néel temperature. This includes band shifts and changes in spectral weight. The team’s observations establish Co 1 / 4 TaSe 3 as a platform for studying altermagnetic materials and their spin-dependent electronic properties. Since the material has antiferromagnetic order with spin-split electronic bands and zero net magnetization, it could be used for studying altermagnetism in spintronic technologies. Have a story tip? Message me here at element14.spintronicsucfarpeson_campusAltermagnetismUniversity of Central Floridauniversityhttps://community.element14.com/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237974Sun, 30 Aug 2026 15:17:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:d30d3b27-af43-44e9-a103-12677c8aeff6shabazIt's some off-the-shelf watering system they installed, just happens to not provide good alerts when the water is low. There is an enclosure and solar panel, so an option is to open up the box and stick it there if there's space (I have not thought the installation through! will leave that to them to figure out : ) The design is a bit ad hoc.. maybe a PCB antenna would have been better all round.https://community.element14.com/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237966Sat, 29 Aug 2026 21:35:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:cfb0ae95-e92c-4f98-b026-e23364916589beacon_dave[quote userid="123345" url="~/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237961"]Incidentally, I was also wondering how to make it more permanent, because I won't be around when this board is installed in an enclosure, it is for a friend to fit in their garden watering "system". They would not know how to re-snap that connector in, if it worked loose. [/quote] Is this some sort of 'extreme watering/gardening' thing we should know about ? Perhaps a couple of holes through the PCB and a thin cable tie or loop of tinned copper wire through them and around the back of the connector ? Could do similar with the cable instead of the Polydoh/UV glue..https://community.element14.com/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237965Sat, 29 Aug 2026 19:56:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:302840c2-a291-4a81-be59-8f1ca64a575dshabazNot a bad idea, since that won't drip inside the connector : )https://community.element14.com/technologies/test-and-measurement/b/blog/posts/bomSat, 29 Aug 2026 19:54:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:e455c7cc-57df-44df-a3f2-a3ccf90e9ed0shortcBOM don't workhttps://community.element14.com/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237964Sat, 29 Aug 2026 19:00:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:6b943746-ce67-409e-975c-0a25de9f4490obonesI'm more of a glue gun kind of guy, but I guess there are reasons not to use that in such a situation .https://community.element14.com/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237962Sat, 29 Aug 2026 18:18:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:a68359e1-44a2-48b1-9ba0-16e6a6d12638beacon_dave[quote userid="17018" url="~/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237919"](and with your tongue in the right angle)[/quote] That's slightly ambiguous - do you have a photo ?https://community.element14.com/technologies/test-and-measurement/f/forum/50334/rf-connectors-assortment/237961Sat, 29 Aug 2026 15:36:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:075b38d5-8e29-41ec-bbe9-5d7f369d3339shabazI gave that a shot!! You're absolutely right, the trick is to hold and look at the coax, and make sure it is parallel to the board. For the snapping-in, I still didn't trust myself, so I ended up finding a short length (about 50mm) of acrylic rod, and pushed with that (it was easy to see that the rod was vertical) although I guess there is a risk it could slide off while pushing. Might place a few-$ order for a 3D-printed tool with any next PCB order. Incidentally, I was also wondering how to make it more permanent, because I won't be around when this board is installed in an enclosure, it is for a friend to fit in their garden watering "system". They would not know how to re-snap that connector in, if it worked loose. The experiment for now (I'm not very happy with it) was to add some strain relief to the coax. I used a small blob of black polydoh, and pressed in the coax to form a cradle to support the wire. Polydoh isn't adhesive, the cradle would slide around, so then I placed a few drops of UV glue on top, and cured that. I might go back and put some other glue onto the connector itself, but I'm unsure since it might seep inside it. Maybe it's already fine. I also still need to add a coating to the board, since it will be outdoors.https://community.element14.com/technologies/test-and-measurement/b/blog/posts/before-i-trust-the-numbers---comparing-three-usb-testers-tenma-72-13540-fnirsi-fb58-keweisi-kws-10va-before-characterizing-the-fnirsi-dps-150Mon, 24 Aug 2026 13:34:00 GMT93d5dcb4-84c2-446f-b2cb-99731719e767:96c6af49-1e1f-43c2-b2e3-da26d250fa91gam3t3chComparing Three USB Testers Before Characterizing the FNIRSI DPS-150 Why I Did This Test I recently added a FNIRSI FNB58 USB tester to the bench with the intention of using it during my characterization of the FNIRSI DPS-150. Before I started trusting the FNB58 numbers, however, I wanted to answer a more basic question: how does it compare with the USB testers I already own, and what effect does each tester have on the circuit it is measuring? That turned what could have been a quick comparison into a useful little measurement exercise. Alongside the FNB58 I tested a Tenma 72-13540 and a low-cost KEWEISI USB tester. Rather than simply plugging each one into a charger and comparing the numbers on their displays, I built a small USB breakout fixture so I could measure the voltage at defined points before and after the tester. The goal here is not to perform a traceable calibration or declare that one inexpensive bench instrument represents absolute truth. The goal is to characterize the measurement chain well enough that I know what each tester is telling me before I use one of them in the DPS-150 project. Figure 1. The characterization bench with the HM310T supply, Multicomp MP730026, and Rev A USB breakout fixture. Building a Fixture So I Could Measure the Same Thing Twice The white Rev A fixture became more important to this experiment than I originally expected. It gives me two clearly defined measurement locations: SOURCE IN and TEST OUTPUT. The source side tells me what voltage is arriving at the USB path, while the output side lets me see what remains after the inline tester and its connectors. Electrically, the SOURCE IN and TEST OUTPUT banana pairs are separate. SOURCE IN feeds the fixed USB-A female connector, while TEST OUTPUT is connected to the flexible USB-A male lead. Inserting the USB tester or device between those two USB connections completes the measurement path. This matters because it is very easy to put one meter on the source side, read another meter downstream, see a difference, and accidentally call that difference an accuracy error. In reality, part of the difference may simply be voltage drop through cables, connectors, PCB traces, shunts, or the tester itself. Fixture point Purpose SOURCE IN Monitor the voltage arriving from the bench supply. USB tester position Insert one USB tester at a time without changing the rest of the setup. TEST OUTPUT Measure the downstream voltage when the tester/output arrangement allows it. No-load baseline Verify that the fixture itself is not introducing a meaningful fixed error before testing meters. With no USB tester or external load installed, I measured approximately 4.989 to 4.990 V at the source and approximately 4.991 V at the test output during the baseline checks. That was close enough for the purpose of this comparison to treat the fixture as effectively transparent at no load. First, I Needed a Working Voltage Reference For the comparison I used my Multicomp Pro MP730026 as the working DC voltage reference. That does not mean I am claiming the Multicomp is a calibrated laboratory standard. It means I wanted one meter, one set of leads, and one measurement method to remain consistent throughout the experiment. Before comparing the USB testers, I checked the Multicomp against the HM310T bench supply at several voltage settings. This was useful because it showed that the disagreement between the HM310T display and the Multicomp was fairly consistent through the most important part of the range. Figure 2. The Multicomp directly monitoring the HM310T during the 5 V reference check. Figure 3. Selecting the appropriate Multicomp range restored the extra displayed digit at the 5 V test point. HM310T setting Multicomp reading Observed difference 1.000 V 0.991 V -9 mV 2.500 V 2.491 V -9 mV 5.000 V 4.990 V -10 mV 10.00 V 9.98 V -20 mV displayed; the Multicomp changed range and lost one display digit. The 1 V, 2.5 V, and 5 V measurements are especially interesting because the difference stays around 9 to 10 mV. At 10 V the Multicomp changed range and the display lost a digit, so I do not want to over-interpret the apparent 20 mV difference there. Figure 4. Reference comparison at the 1 V setting. Figure 5. Reference comparison at the 2.5 V setting. Figure 6. The 10 V point, where the Multicomp changed range and displayed less resolution. The Three USB Testers Although all three devices can be called USB testers, this experiment reinforced that they are not really aimed at the same job. Tester How I see its role What stood out during this test KEWEISI Low-cost quick-check meter Simple and fast. Useful for confirming that USB power exists, but its current display was too coarse for the small LED load. Tenma 72-13540 Everyday service/troubleshooting tester Bright, readable LCD and by far the lowest observed self-consumption of the three. FNIRSI FNB58 USB characterization/analyzer Much finer displayed resolution, low-current measurement, accumulated measurements, protocol tools, cable functions, and PC/software capability. The FNB58 also goes well beyond the voltage/current comparison performed here. Its feature set includes USB fast-charge protocol detection and triggering, PD monitoring, D+/D- measurements, cable resistance functions, E-Marker support, accumulated capacity and energy, waveform functions, and PC software support. Those features deserve their own deeper review later. For this test I deliberately kept the question narrow: can I understand and trust its basic voltage and current behavior well enough to use it in the next project? Resolution is not the same thing as accuracy A display reading 4.97064 V is showing much more resolution than a display reading 4.97 V or 5.02 V, but extra digits alone do not prove that every digit is absolutely accurate. This comparison is about observed agreement and useful measurement resolution, not traceable calibration. No-Load Test: The Meter Is Part of the Circuit The first result that really changed how I looked at these testers was their own current consumption. With nothing connected to the downstream USB output, the HM310T still showed current being drawn. Tester HM310T current with no downstream load Approximate tester burden Tenma 72-13540 0.004 A 4 mA KEWEISI 0.029 A 29 mA FNIRSI FNB58 about 0.059 to 0.060 A about 59 to 60 mA That approximately 60 mA seen by the bench supply when the FNB58 is operating is not 60 mA of DUT current. It is largely the FNB58 powering itself. The color display, processor, ADC and USB/protocol circuitry all need power. The FNB58's own downstream current channel was essentially at zero with no external load. The Tenma was particularly impressive here. Its approximately 4 mA upstream draw was dramatically lower than the other two testers. Figure 7. KEWEISI no-load baseline. The HM310T sees approximately 29 mA of total current. Figure 8. Tenma no-load baseline. The HM310T sees only approximately 4 mA. Figure 9. FNB58 no-load baseline. The supply sees roughly 60 mA while the downstream current measurement remains essentially zero. Voltage Accuracy: The Measurement Point Matters The early FNB58 measurements produced an apparent disagreement that initially looked much larger than expected. The Multicomp was measuring the source input while the FNB58 was reporting its own internal/downstream voltage. Those are not necessarily the same electrical point. Once I moved the Multicomp to a comparable downstream point and repeated the installation, the result changed significantly. In one simultaneous snapshot the Multicomp was around 4.971 V while the FNB58 showed 4.97064 V, a difference of only about 0.36 mV at that instant. That demonstrates very close indication agreement at the same electrical node under this particular test condition; it does not establish 0.36 mV absolute accuracy or constitute a calibration of the FNB58. Tester Multicomp at comparable point USB tester display Observed difference KEWEISI about 4.980 V 5.02 V about +40 mV Tenma 72-13540 about 4.988 V 5.02 V about +32 mV FNIRSI FNB58 about 4.971 V 4.97064 V about -0.36 mV at one simultaneous snapshot I also observed an earlier FNB58 downstream measurement that eventually settled around 4.915 V. Because a controlled reinstall and repeat produced approximately 4.971 to 4.975 V instead, I am keeping the earlier result as an anomalous startup/connection-state observation rather than treating it as the normal insertion loss of the FNB58. The Small USB LED Became the Most Useful Test For a repeatable low-current load I used a small flexible USB LED light. It turned out to be an excellent way to expose the practical difference between these meters. With the KEWEISI installed, the HM310T total current increased from approximately 29 mA to approximately 46 to 47 mA. The light was clearly operating, but the KEWEISI continued to display 0.00 A. With the Tenma installed, the HM310T increased from approximately 4 mA to approximately 21 to 22 mA. Again, the LED operated normally, but the Tenma displayed 0.00 A. Both of those supply-side changes suggest that the LED itself was drawing roughly 17 to 18 mA. The FNB58 directly resolved the load. With the LED connected, it displayed approximately 0.01681 A and 0.08353 W at roughly 4.969 V. That is approximately 16.8 mA, which agrees very well with the current inferred from the supply-side subtraction. Tester No-load upstream current Upstream current with LED Tester current display KEWEISI ~29 mA ~46-47 mA 0.00 A Tenma 72-13540 ~4 mA ~21-22 mA 0.00 A FNIRSI FNB58 ~59-60 mA ~65 mA ~0.01681 A Figure 10. The FNB58 directly resolving the small LED load at approximately 16.8 mA and 83.5 mW. For me, this was the clearest result of the entire comparison. The KEWEISI and Tenma were not necessarily failing to pass the current correctly; their displays simply did not provide useful information at this current level. The FNB58 did. What About Voltage Drop Through the Testers? Because the fixture exposes both sides of the USB path, I could also get a feel for how much the measurement setup itself was disturbing the circuit. At the controlled no-external-load points, the Tenma showed roughly 1 mV of source-to-output difference while drawing about 4 mA, the KEWEISI roughly 7 mV at about 29 mA, and the controlled FNB58 repeat roughly 13 mV at about 60 mA. Tester Approx. self-current Observed source-to-output drop Important caveat Tenma 72-13540 4 mA ~1 mV Very small values; do not treat this as a calibrated resistance measurement. KEWEISI 29 mA ~7 mV Includes the complete connection/test path. FNIRSI FNB58 59-60 mA ~13 mV on controlled repeat The earlier ~4.915 V result was anomalous and is not used here. With the KEWEISI and LED operating, I measured approximately 4.988 V at SOURCE IN and approximately 4.968 to 4.971 V downstream, giving roughly 17 to 20 mV of total observed drop in that loaded arrangement. I do not want to turn those numbers into a claimed shunt resistance because the HM310T current includes the tester's own electronics and the exact internal current path is not identical between products. What the test does demonstrate is that an inline USB meter is not electrically invisible. So Which Tester Would I Actually Use? After doing the measurements, I do not think there is one universal winner. There is a clear winner for the DPS-150 characterization, but each tester still makes sense for a different job. Tester Best use Example KEWEISI Fast go/no-go USB troubleshooting Check whether 5 V is present, whether a cable is open, or whether a charger is obviously collapsing under load. Tenma 72-13540 Everyday bench or service work Quick charger, cable and power-bank checks where a readable display, simple operation and low tester burden are valuable. FNIRSI FNB58 Measurement and characterization Low-current devices, voltage/current/power logging, cable analysis, USB protocol work, PD investigation and more detailed engineering tests. Personally, I really like the Tenma as the quick everyday meter. The LCD is bright and easy to read, the unit is uncomplicated, and its own current draw was the lowest of the three by a large margin. The inexpensive KEWEISI still has a place. If I only want to know whether a USB cable has power or whether a charger is somewhere in the right neighbourhood, I do not need a color-screen analyzer with protocol decoding. For the characterization work performed here, however, the FNB58 is the preferred inline tester of these three. The small LED test demonstrated why: a roughly 17 mA load disappeared below the useful current display resolution of the simpler meters, while the FNB58 measured it directly. This selection is based on the conditions tested so far and should not be read as a claim that the FNB58 is universally accurate or calibrated. The Measurement Chain I Will Use for the DPS-150 This comparison was really a prerequisite for the next project. I now have a much better idea of how I want to divide the measurement jobs when I start characterizing the FNIRSI DPS-150. Instrument Role DPS-150 / bench source Device under test or controlled source. Its own display is recorded but not automatically treated as the reference. Multicomp MP730026 Working DC voltage reference at a clearly defined physical test point. FNIRSI FNB58 Inline downstream USB voltage, current, power and protocol analyzer. Rev A USB breakout fixture Provides repeatable SOURCE IN and TEST OUTPUT access so cable and insertion losses can be investigated. Oscilloscope Ripple, noise, startup behavior and transient measurements rather than precision DC voltage reference. For loaded measurements I will record the Multicomp voltage at the defined source or downstream point, the FNB58 voltage/current/power, and the source supply's total current. The important rule is that I will not compare two voltage readings as an accuracy test unless they are measuring the same physical node under the same operating condition. I will also keep the FNB58's roughly 60 mA upstream self-consumption in mind. That current is part of what the source sees, but it is not automatically part of the downstream DUT current reported by the FNB58. What This Test Does Not Claim • This is not a traceable calibration. I did not use a calibrated voltage or current standard. • The current work is a baseline confidence characterization, not a complete FNB58 calibration. Future testing should include controlled load points around 0.1 A, 0.5 A, 1 A, 2 A and higher where the equipment safely allows, broader voltage-range checks, insertion loss, repeatability, resolution/noise, warm-up and thermal drift, and operating-range dependence. • I have not measured long-term temperature drift or repeatability over many hours. • Advanced FNB58 functions remain a later characterization phase. These include charging-protocol detection/triggering, PD monitoring, E-Marker functions, cable resistance, waveform tools, Bluetooth/PC connectivity and long-term logging. • The exact KEWEISI model/revision matters. Similar-looking low-cost testers can use different internal hardware and published specifications. A Vintage-Meter Detour for Another Project I also briefly brought an older Micronta autoranging digital multimeter into the reference checks. It was interesting enough that I decided not to mix it into the USB-tester conclusion. At approximately 1 V the Micronta indicated 0.997 V while the Multicomp indicated 0.991 V. At 2.5 V it indicated about 2.502 V versus 2.491 V on the Multicomp, and near 5 V it indicated roughly 5.04 V versus 4.990 V. The changing difference deserves a proper characterization of its own. That may become a future GAM3T3CH project: take a collection of older digital and analog meters, compare them against modern bench equipment, and see how well they have survived the decades. Figure 11. Optional sidebar image from the Micronta comparison near 1 V. Figure 12. Optional sidebar image from the Micronta comparison near 5V. Final Thoughts The biggest thing I learned from this exercise was not simply that the FNB58 has more digits or more features. It was that every measurement instrument becomes part of the system being measured. The KEWEISI is still useful as a cheap sanity checker. The Tenma turned out to be a very nice everyday USB tester and had remarkably low self-consumption in this test. The FNB58 is the one I will carry forward into the DPS-150 characterization because its resolution and feature set make it much more useful when I actually need to quantify what is happening. Most importantly, I now know how to interpret the numbers it gives me. I know that the source sees current used by the FNB58 itself. I know that source-side and downstream voltage are not automatically interchangeable. And I know that a meter showing more decimal places still needs to be checked against a sensible reference before those digits mean anything. At this stage I consider the FNB58 validated as the preferred inline USB tester for the next DPS-150 measurements within the conditions explored here. That is a practical confidence decision, not a declaration of universal accuracy. The broader characterization remains open and will continue as controlled loads, voltage range, thermal behavior and the FNB58's advanced functions are tested. That was the whole point of building the fixture and doing this comparison before moving on to the DPS-150: establish the measurement chain first, then characterize the device. References / Product Information Tenma 72-13540 product information: 72-13540 TENMA, Voltage Tester, LCD, USB | Newark Electronics FNIRSI FNB58 product information: FNIRSI product documentation and software-download information. KEWEISI background: product-specific information varies by revision; published KWS-series teardown/characterization material can be used as supporting context rather than as a specification for every KEWEISI-branded unit. There is a bunch of reviews on the one I used in this out there I think its labeled as the KEWEISI KWS-10Va. here is another test result of this unit from eevblog user of a similar unit not sure if 100% same model or not.testingkeweisiusb testertenmahanmatekmulticompFNIRSI