LCR Meter Accuracy - Page 1
Forum section: electronics / testgear

author: y2khris
author_rank: Contributor
timestamp: August 02, 2016, 05:42:56 pm
content: Hi guys, I have been looking at LCR meters for a while now and it is one piece of equipment that I am having a hard time pulling the trigger on. I have seen the DER EE DE-5000, the various hand held Agilent, and the full size Agilent (most likely HP as I have a somewhat limited budget) and I was wondering what is the best way to go in terms of accuracy, flexibility, data logging and longevity. I have been using a function generator and oscilloscope to measure ESR and have made a calculator tool that let's me put in a few of the values and I get the ESR of the capacitor.I figure the full size ones are more accurate because they offer a wider frequency range to test with but I am unsure of what is actually needed and what is the best bang for the buck (I know it's probably the Der EE, but I would rather not).I have been looking at the following models:HP 4262A (the 4261A only goes up to 1KHz)Agilent U1731C (Seems kind of pricey for a handheld tool that only goes up to 1KHz)Agilent U1733C (Goes up to 100KHz, but costs around $100 more than the U1731C)HP 4274A (5 1/2 digits, versus the ones above that are 3.5, the 4275A goes up to 10MHz but only goes down to 10KHz)HP 4263B (Accurate, nice display, modern but it costs an arm and a leg and I would have to save up for a while to get one)I know somebody out there knows enough about this stuff to help me out.

author: nctnico
author_rank: Super Contributor
timestamp: August 02, 2016, 07:53:30 pm
content: I used to own a HP4274A but I sold it again because for it's size it couldn't do much and for measuring low resistance (milli-Ohms) it was useless. For now I'm using this one:http://www.ebay.com/itm/Auto-LCR-Digital-Electric-Bridge-Resistance-Capacitance-Inductance-ESR-Meter-/171199475262but it doesn't have data logging or remote control so even though it is pretty accurate it's use is very limited.One that interests me very much is this one because it has a reasonable frequency span, can apply DC voltages/currents and it costs around $1200 including shipping:http://www.ebay.com/itm/Hi-accuracy-0-05-LCR-Meter-50Hz-200KHz-14K-Frequency-Points-TFT-LCD-USB-RS232-/272298505240It is from a brand called ZXP (http://www.zxptest.com/eng/) and with some digging the English manuals can be found for similar models. There are tons of similar LCR meters on Ebay from Applent and Tonghui; I get the feeling a lot gets copied.

author: TurboTom
author_rank: Super Contributor
timestamp: August 02, 2016, 08:20:31 pm
content: At that price tag I wouldn't hesitate to get the Applent:http://www.ebay.com/itm/Applent-AT826-USB-Handheld-LCR-Meter-100kHz-LCR-Meter-Portable-LCR-Meter-New-/261672893309?hash=item3ceceb7b7d:g:dkgAAOxyaTxTU58CI've got one of these (paid a little more than this) and didn't regret the purchase. Compact, reasonable frequency range and pretty accurate.Cheers,Thomas

author: TheSteve
author_rank: Unknown
timestamp: August 02, 2016, 08:25:01 pm
content: You could contact this guy and see if he has anymore U1733C's - they are a nice product.https://www.eevblog.com/forum/buysellwanted/fs-agilent-branded-u1733c-lcr-meters/

author: Deckert
author_rank: Regular Contributor
timestamp: August 02, 2016, 10:16:10 pm
content: Hi,The problem (for me) is that an LCR meter is not something I use that often - I use my multimeters far more. But when you do need an LCR meter, boy, you really do need a decent one.I made a video a while back, detailing my experience with the ISO-Tech LCR-1701 LCR Meter. I'm not advocating that you get it, especially not if you can source the DE-5000, but it uses the same chipset (from Cyrustek) as the DER EE DE-5000 meter, so you'll get an idea of what it's capable of. The DE-5000 is just not available in my country.https://www.eevblog.com/forum/testgear/iso-tech-lcr-1701-teardown-and-review/Most importantly, I've realised that I need a handheld device, not one tied to a bench. YMMV due to different requirements though. As a hobbyist, fixing the odd switch-mode supply and testing reclaimed caps, it's rather useful from time to time.If you're mainly interested in measuring ESR, then have a look at the Peak Atlas ESR70. Steve Gardner over on SDGEE did a really great review of it (look for video SDGEE #010 on YT).--deckert

author: Dwaine
author_rank: Frequent Contributor
timestamp: August 03, 2016, 02:45:54 am
content: Quote from: nctnico on August 02, 2016, 07:53:30 pmHow are you liking the XJW01 LCR meter? I'm thinking about buying the XJW01 LCR meter, but it's a toss up between it and the Applent AT2817A or AT817D.

author: y2khris
author_rank: Contributor
timestamp: August 03, 2016, 03:18:37 am
content: Quote from: nctnico on August 02, 2016, 07:53:30 pmSo, regarding the HP4274A, not taking the low resistance measurements into account, you got rid of it because it doesn't have many capabilities that new LCR meters have?Quote from: nctnico on August 02, 2016, 07:53:30 pmSeeing as how they are similar in price, what do you think of the capabilities of the HP 4263B versus the ZXP?

author: y2khris
author_rank: Contributor
timestamp: August 03, 2016, 03:22:37 am
content: Quote from: TurboTom on August 02, 2016, 08:20:31 pmThe screen looks really nice on the Applent; how does it compare to the EE 5000? Is it more accurate than the aforementioned HP LCR meters, maybe with the exception of something expensive like the 4263A?

author: nctnico
author_rank: Super Contributor
timestamp: August 03, 2016, 11:54:34 am
content: Quote from: y2khris on August 03, 2016, 03:18:37 amIt is nice but the number of test frequencies is very limited.QuoteAccording to the specs (14000 different test frequencies) the ZXP would allow to make a fine grained plot of Q versus frequency of a component where the 4263B can only do a few standard frequencies. In my case the 100kHz of the 4263B would not be high enough. The 4263B is also missing DC bias abilities which are handy to check the voltage dependant behaviour of high capacity MLCC capacitors.

author: pascal_sweden
author_rank: Super Contributor
timestamp: January 27, 2017, 03:01:58 pm
content: Quote from: y2khris on August 02, 2016, 05:42:56 pmCan you elaborate more on the manual method using a signal generator and an oscilloscope?How come that there is no software tool for Rigol or Siglent, that uses LXI to automatically control the LXI-enabled signal generator and the LXI-enabled oscilloscope in order to measure the ESR value and the Q factor?

author: Deckert
author_rank: Regular Contributor
timestamp: January 27, 2017, 09:52:40 pm
content: Hi,Manual measurement using a scope and a sig-gen:And measuring ESR:Why use very expensive tools when you can use something that's a lot simpler, quicker more accurate and a lot more portable?--deckert

author: Vtile
author_rank: Super Contributor
timestamp: January 27, 2017, 11:58:13 pm
content: There is also application note for this age old Gen&scope method from IIRC tektronixs. Atleast for hobbyist use it might be suitable, I have seen a few methods of this. The one that finds 1/2 division frequency were simpler to use with low end gear .. IIRC.This is basic voltage divider and calculation against known resistor.http://www.tek.com/document/application-note/capacitance-and-inductance-measurements-using-oscilloscope-and-function-ge

author: shteii01
author_rank: Frequent Contributor
timestamp: January 28, 2017, 12:22:09 am
content: Quote from: Deckert on January 27, 2017, 09:52:40 pmCool stuff. Thank you for posting it.But. That dude got Tek 2467! That was top of the line 'scope. I would not want to do all that stuff on purely analog scope.

author: drkirkby
author_rank: Newbie
timestamp: September 01, 2018, 10:13:47 pm
content: Quote from: y2khris on August 02, 2016, 05:42:56 pmOkay, I know this topic is a bit old, but the HP 4263A is a cheaper than the 4263B you found too expensive. The differences between the A and B models are given on the Keysight website and seem pretty minor, to be honest.I don't know if this link will work - it loadsveryslowly for me:https://www.keysight.com/main/editorial.jspx?cc=US&lc=eng&ckey=1498485&nid=-32776.536879695&id=1498485If not, search for the text "What are primary differences between the 4263A and 4263B?" (blame Keysight for missing out the word "the" before "primary" - not me)but the shows that:1) The 4263B can select from 3, 4 or 5 digits, but the 4263A can only display 5 digits. That is a pretty insignificant feature! I'm sure we can round that if we want.2) The 4263B has current and voltage monitoring, but the 4263A does not.3) The 4263B has a "show settings" feature, to display all the settings, whereas the 4263A does not.4) The 4263B can display the open/short/load compensation values, but the 4263A can not. But the 4263A still does the compensation.None of those differences would put me off the 4263A. I would certainly choose it over the Chinese meters people are talking about. Note the Chinese meters are not supplied with coaxial cables, but the 4TP connection on the HP meters should use coax, and the coax has to be a specific length (1 m).I picked up a used HP 4263A in August 2018, that had Agilent calibration stickers on the screws, but no cal sticker on the front. I rather suspect that means it had been back for calibration, but not in the last 5 years. I only did a quick test, but a 100 ohm 0.005% resistor read 100.00 ohms, with a few nH of inductance!The annoying thing about the 4263A and 4263B is their limited choice of test frequencies. (100, 120, 1000, 10000, and 100,000 Hz), with 20 kHz as an option.I have a 4284A (20 Hz to 1 MHz), which sell for a lot of money. That has over 8000 test frequencies, but they are very poorly chosen. There is 20 Hz, and 20.01 Hz, but nothing between 750 kHz and 1 MHz. So it has some frequencies so close together to be useless, and others so far apart.Dave.

author: David Hess
author_rank: Super Contributor
timestamp: September 01, 2018, 11:03:40 pm
content: It is difficult for me to recommend anything except the DER EE DE-5000 for casual use because of its low cost. It covers the basics including measurements at 100kHz which are commonly specified.If I wanted something better but at a significantly higher cost, I would look for a low frequency network analyser instead.

author: drkirkby
author_rank: Newbie
timestamp: September 01, 2018, 11:40:31 pm
content: Quote from: David Hess on September 01, 2018, 11:03:40 pmThe DE-5000 was a product made by the reputable company IET labs. I don't have a direct link, but herehttps://www.ietlabs.com/de6000-lcr-meter.htmlit mentions the DE-6000 is an improvement on the DE-5000.Now there are other DE-5000's around, that will no doubt claim the same specifications as the IET Labs instruments, but I suspect are probably inferior.A network analyzer and an LCR meter are very different sort of instruments. VNAs are not designed to work at very low or very high impedances - only impedances close to that of their bridge, which is normally 50 ohms.I have here* HP 8720D VNA (50 MHz to 20 GHz)* HP 8753 VNA (300 kHz to 3 MHz)* HP 4291B impedance/'material analyzer (1-1800 MHz)* HP 4284A precision LCR meter (20 Hz to 1 MHz)* HP 4263A LCR meter (100 Hz to 100 kHz). This is surplus to my requirements, as I only bought as it was sold with the Kelvin test leads.For very low or very high impedance values, the LCR meters are best. For more modest impedance values, instruments based on the RF-IV technique, like the 4291B are more suitable and have a wider frequency range. For the widest frequency range, VNAs are best, but they are not suitable for low or high impedances.Yes, there are tricks one can do with a VNA to handle higher or lower impedances, by not using a direct connection. But they will not approach the accuracy of an LCR meter.The instrument I would like to get my hands on is an HP 4285A LCR meter (75 kHz to 30 MHz), but unfortunately, they are damn expensive.Dave

author: David Hess
author_rank: Super Contributor
timestamp: September 02, 2018, 05:56:56 am
content: That is why I said "low frequency network analyser" instead of vector network analyser. They make special ones for testing components. Analog Devices even sells DDS ICs specifically intended for them.It is one of those things which I have been tempted to design for myself and maybe make available.

author: drkirkby
author_rank: Newbie
timestamp: September 02, 2018, 08:22:27 am
content: Quote from: David Hess on September 02, 2018, 05:56:56 amCan you give me an example of such an instrument bf one of the manufacturers of high-end test equipment, such as Anritsu, Rohde &Schwarz, IET labs, Keysight, Tektronix, Keithley etc? What impedance range do they cover, and what sort of frequency range?Any such instrument must be able to measure the vector of the impedance.I've personally never seen anything commercially available that can cover such a wide frequency range as the LCR meters, but it is not something I have looked for to be honest.I just performed a quick literature review and did not manage to find much, but I'm sure there must be some "review papers" on the subject of impedance measurements.Dave

author: nctnico
author_rank: Super Contributor
timestamp: September 02, 2018, 09:36:47 am
content: Quote from: drkirkby on September 01, 2018, 11:40:31 pmThis statement isn't quite true. There are several ways a VNA can be build and the ones with a lower frequency range (tens of Hertz or lower) have several methods of measuring which allows to measure very low and very high impedances.

author: ogden
author_rank: Super Contributor
timestamp: September 02, 2018, 10:31:32 am
content: Quote from: drkirkby on September 02, 2018, 08:22:27 amHere you go:https://www.omicron-lab.com/products/vector-network-analysis/bode-100/

author: David Hess
author_rank: Super Contributor
timestamp: September 02, 2018, 03:05:30 pm
content: Quote from: drkirkby on September 02, 2018, 08:22:27 amI do not know about the others but HP/Agilent/Keysight has had them for a long time. Today they are calling them "impedance analyzers". Internally they are essentially a low frequency one port vector network analyser optimized for precision instead of frequency range.https://www.keysight.com/en/pc-1000000382%3Aepsg%3Apgr/impedance-analyzers?nid=-33831.0&cc=US&lc=enghttps://www.keysight.com/en/pc-2461685/impedance-analyzers?nid=-32775.0.00&cc=CZ&lc=engHioki has them alsobut I do not know anything about the company.Another oneI remember running across.Analog Devices makes adedicated DDS ICfor this and even anevaluation kit. I am a little surprise there is not a commercial produced based on the AD5933 but maybe I have just not found it yet.QuoteI always have troubling finding them because nobody uses a common name to describe them. Essentially they are the vector network analyser version of an LCR meter.

author: ogden
author_rank: Super Contributor
timestamp: September 02, 2018, 03:22:17 pm
content: Quote from: David Hess on September 02, 2018, 03:05:30 pmIncorrect. Fact that 1-port VNA and IV impedance analyzer both have 1 port, does not make them equal.Further reading:https://literature.cdn.keysight.com/litweb/pdf/5950-3000.pdfChapter "2.6 Difference between RF I-V and network analysis measurement methods"

author: bugi
author_rank: Regular Contributor
timestamp: September 02, 2018, 06:05:38 pm
content: Quote from: David Hess on September 02, 2018, 03:05:30 pmMay have something to do with "Capable of measuring of 100 Ω to 1 kΩ with additional circuitry" (and only 1k+ as is) (and note, it is about impedance, not just resistance). It seems to get quite tricky in that 100 to 1k range, and I don't think there would be many customers for a general purpose measurement device that does not go below 100 ohm.That chip seems to be aimed at special purpose devices, where its features and limitations have a better fit for the purpose, and where it is possible to tweak the circuitry to match the specific needs.Quote from: drkirkby on September 01, 2018, 11:40:31 pmThere are already some threads here having some talk on that DE-5000 (and 6000) stuff, and my poor memory has collected something along the lines that DER is now making the same thing, maybe it was the original manufacturer of it for IET or something, and is now selling them to sooo many different sellers. The devices seem to now come with varying changes in what components are left out and/or replaced for saving a cent or two. They seem to work ok (with some quirks) and more or less "to the specs" (at least once the user remembers to do the calibration process). Also, it has been said that the IET's DE-6000 "improvements" were quite insignificant, and definitely not worth the price difference to DER's DE-5000. Of course, now IET part of the story is just a historical note, since IET discontinued both models (and "replaced" 6000 with a huge bench box with price as "request a quote", which typically means too expensive to be shown publicly...).

author: Wolfgang
author_rank: Super Contributor
timestamp: September 03, 2018, 05:04:34 pm
content: ... there is a Keysight E5061B-3L5 with a range from 5Hz (!) to 3GHz.This seems to be the holy grail of VNA impedance measurements, and there are a load of Keysight appnotes how to measure very high or very low impedances.Problem: Severe wallet drain.

author: David Hess
author_rank: Super Contributor
timestamp: September 03, 2018, 06:40:40 pm
content: Quote from: bugi on September 02, 2018, 06:05:38 pmThe application notes show that the measurement range can be extended even beyond that but even with those limitations, it would be useful where common LCR meters are not. I suspect though that anybody who knew how to make best use of it does not need it and could just make their own design without it from scratch which is certainly what I would consider doing.QuoteI suspect the only reason the part is economical to produce is that it has a wide applicability to specialized transducer measurements where it can operate over a limited range of frequency and impedance.

author: Wolfgang
author_rank: Super Contributor
timestamp: September 03, 2018, 06:46:34 pm
content: Hi David,I've never seen the new AD parts in action in a measurement instrument. It looks that they are simply no competition for a "real" VNA from milliohms (PDNs) to 100Ks (crystals).

author: JohnPi
author_rank: Regular Contributor
timestamp: September 03, 2018, 08:54:49 pm
content: I just made a software Vector Network Analyzer (VNA) with my Rigol 1054Z and Siglent DS1025. It works from 1 Hz to 25 MHz and creates great plots and log files. I haven't added the software to de-embed the probes (or done extensive calibration), but that won't take long. Take a look at:https://github.com/jp3141/Vector-Network-Analyzer. You don't need anything extra other than a resistor.Here's an example output:p.s. I also have a DE-5000 and am happy with it, although I wish it also had a 10 kHz test frequency.

author: Wolfgang
author_rank: Super Contributor
timestamp: September 03, 2018, 08:58:41 pm
content: Looks interesting, do you have an idea about the dynamic range your solution can provide ?

author: JohnPi
author_rank: Regular Contributor
timestamp: September 03, 2018, 09:34:19 pm
content: With the signal generator putting out 10 V, and the scope with 1 mV/division (closer to 100 uV/step) that calculates to 100 dB, but I don't expect much more than 70 dB. I just got it working and haven't had time to stress it yet (feel free to hack it). The scope only claims 80 dB or so isolation between channels.It uses as much data as will fit in a 30 k sample window and extracts (correlates) the signal components at the test frequency. SNR is reasonable -- I think I pick up more from my environment and stray coupling (e.g. 10 V to 1 mV input range is actually hard to isolate). As you can see, though, the plots are quite smooth.Here's a partial output from the log file showing 200 points per decade (stepping from 1 MHz to 10 MHz). Data is quite noise-free (Note the raw Sin/Cos phase varies because of the t=0 trigger point of the scope; it doesn't affect the results):Code:Sample 196, 9549925.860 Hz, 500 MS/s, 59948 points; 1145 cycles @ 52.4/cycleCh1: Sin, Cos = 1.6443, -1.5963; Mag = 4.58345, Phase = -44.15 deg.Ch2: Sin, Cos = 0.0063, 0.0021; Mag = 0.01333, Phase = 18.06 deg.Ch2:Ch1 = -50.73 dB @ 62.21 deg.; Z = 1.3513 +j 2.5805Sample 197, 9660508.790 Hz, 500 MS/s, 59986 points; 1159 cycles @ 51.8/cycleCh1: Sin, Cos = 0.1239, 2.2847; Mag = 4.57618, Phase = 86.90 deg.Ch2: Sin, Cos = -0.0058, 0.0035; Mag = 0.01350, Phase = 148.84 deg.Ch2:Ch1 = -50.61 dB @ 61.94 deg.; Z = 1.3825 +j 2.6099Sample 198, 9772372.210 Hz, 500 MS/s, 59965 points; 1172 cycles @ 51.2/cycleCh1: Sin, Cos = -2.2754, -0.2295; Mag = 4.57382, Phase = -174.24 deg.Ch2: Sin, Cos = -0.0026, -0.0063; Mag = 0.01368, Phase = -112.60 deg.Ch2:Ch1 = -50.49 dB @ 61.64 deg.; Z = 1.4156 +j 2.6388Sample 199, 9885530.947 Hz, 500 MS/s, 59987 points; 1186 cycles @ 50.6/cycleCh1: Sin, Cos = 0.0164, -2.2851; Mag = 4.57037, Phase = -89.59 deg.Ch2: Sin, Cos = 0.0061, -0.0033; Mag = 0.01385, Phase = -28.25 deg.Ch2:Ch1 = -50.37 dB @ 61.34 deg.; Z = 1.4482 +j 2.6658Sample 200, 10000000.000 Hz, 500 MS/s, 60000 points; 1200 cycles @ 50.0/cycleCh1: Sin, Cos = 1.5814, -1.6418; Mag = 4.55909, Phase = -46.07 deg.Ch2: Sin, Cos = 0.0068, 0.0018; Mag = 0.01401, Phase = 14.97 deg.Ch2:Ch1 = -50.25 dB @ 61.04 deg.; Z = 1.4830 +j 2.6969DoneI intend to do a de-embedding step where I loop though the frequency steps without the unit-under-test connected and store that data to subtract from the measurements. However to expect 80 dB at 10 MHz needs a more sophisticated test fixture than a few crocodile clips.

author: ogden
author_rank: Super Contributor
timestamp: September 03, 2018, 09:35:05 pm
content: Quote from: JohnPi on September 03, 2018, 08:54:49 pmExcellent work! Plots (luckily for you) are great indeedQuoteYou mean open/short/load calibration? Indeed needed.For owners of other than Siglent generator - could you possibly craft RLC software for manually configured generator frequency? I don't mind to manually set my generator to 100 KHz or 1MHz so I can measure capacitor or inductor at given frequency.Some (not me) could maybe manufacture RLC add-on PCB with 1/10/100/1000 KHz generator on-board to have decent RLC meter that needs only Rigol 1054Z and your software

author: Wolfgang
author_rank: Super Contributor
timestamp: September 03, 2018, 09:44:31 pm
content: Looks fine to me, congrats !!I had a similar idea of using a signal generator and a scope, but mine was using just one RIGOL MSO1104ZS (this one has built-in generators), so no extra generator would be needed. Instead of a swept input I planned to use a bandwidth-limited noise signal, and also a correlaction/coherence/FFT approach to fiddle out phase and gain.More info can be found here:electronicprojectsforfun.wordpress.com/a-loop-stability-measurement-solution-for-the-poor/The intended purpose was Bode plots and the measurement of power supply output impedances.The injector is ready, but what is still missing is a reference instrument to control my measurements. In late September, I will get my hands on a Keysight E5061B-3L5 (5Hz to 3GHz VNA) and on an Omicron Bode100, so I can make a lot of sample measurements that I can then compare with my approach. I will update my website as new results arrive.Much success !

author: JohnPi
author_rank: Regular Contributor
timestamp: September 03, 2018, 09:46:35 pm
content: QuoteYou could modify this line in the code:Code:SDG1025.write("C1: BSWV FRQ, %11.3f" % TestF)to pause and ask the user to manually set the frequency. That's all it would take. However, don't expect any precision better than you set the signal source frequency -- the VNA correlates to this, and a frequency discrepancy will give unpredictable errors. With some work, you could add a frequency measurement loop to the software to remove this issue.QuoteAn Arduino (e.g.https://www.pjrc.com/store/teensy32.htmlwould work well for this. It doesn't even need good sine waves -- because the VNA only extracts the fundamental sinusoid from the signal. You could also control the Arduino over serial/USB from Python also. Because the VNA measures both the forcing function and the response, it can use nearly any signal; you just need the frequency set correctly.

author: JohnPi
author_rank: Regular Contributor
timestamp: September 03, 2018, 09:51:04 pm
content: QuoteThat's a nice idea using a combined scope/generator.Your SNR and dynamic range (30 dB only ?) will be horrible with a noise source and FFT. The scope doesn't have enough ADC resolution (8 bit) to remove the noise (in a reasonable time).The Omicron Bode100 uses a 24-bit ADC and dedicated DSP to get great SNR and fast sweep speeds (mine takes about 100 points/minute).

author: Wolfgang
author_rank: Super Contributor
timestamp: September 03, 2018, 09:59:59 pm
content: Its clear that the noise technique will need some averaging. On the other hand, I can take relatively long samples and I know what to look for - that could be used to cut noise down. On the other hand, noise instead of swept signal reduces the probability of dynamic range problems in case of resonances. Furthermore, the output noise spectrum can be screened for harmonics of the input.Dont worry, its just a try and I am curious how far I can get.

author: ogden
author_rank: Super Contributor
timestamp: September 03, 2018, 10:01:51 pm
content: Quote from: JohnPi on September 03, 2018, 09:46:35 pmIt was just "two cents" about how *you* can improve your "product".QuoteInteresting.. You are not using DCT? (I did not read code and most likely will not)Did you test using square wave? Any side by side results to confirm that "It doesn't even need good sine"?

author: JohnPi
author_rank: Regular Contributor
timestamp: September 03, 2018, 10:07:28 pm
content: QuoteYou'll need to average over N^2 measurements to improve performance by a factor of N. Rather than look for a single frequency each time, you can extract all data for a single band simultaneously (i.e. with the same set of measurements). However you won't be able to cover (e.g.) 1 Hz to 10 MHz in one band -- perhaps a band could only cover 1 decade ?My technique steps frequencies and stops & measures at each one; I'd like to understand how I could use a non-stop frequency sweep instead, but that would require good correlation between the expected frequency and correlation signal -- it's more math and coding than I want to do right now. Something like this is used for audio analysis, and is useful for finding distortions, but that's not what I am looking for -- I expect a linear system.

author: JohnPi
author_rank: Regular Contributor
timestamp: September 03, 2018, 10:09:53 pm
content: Quote from: ogden on September 03, 2018, 10:01:51 pmNo. Feel free to peruse the code if you are interested in the details.

author: ogden
author_rank: Super Contributor
timestamp: September 03, 2018, 10:20:59 pm
content: Quote from: JohnPi on September 03, 2018, 10:09:53 pmI am interested as far as you are.  it seems you are not because to three questions of mine you simply answered "no"Look, I like (idea of) what you made but don't need it. All my interest here is: talk you into improvements, obviously only in case you wish to.

author: Wolfgang
author_rank: Super Contributor
timestamp: September 03, 2018, 10:33:57 pm
content: Hi, sorry for not saying earlier, my intended application for Bode plots and PDN impedance needs to go up to a few 100kHz only.I am measuring linear power supplies only, because I need the for noise measurements (no switching residue allowed here).Some sample PSUs:https://electronicprojectsforfun.wordpress.com/power-supplies/battery-operated-power-supplies/The issue here is not the RFI introduced by a switcher or line input, but the noise existing in the regulators itself. This, along the theoutput impedances, is what I want to measure.To the second part of your question:In a swept approach as you have it, you measure one frequency at a time. You start your generator, let it settle, measure input and output by amplitude and phase and compute a transfer function point by point.In a random appoach, you use white noise. White noise has a flat spectrum. If you time-sample the input signal (into 50Ohms) and FFT it, a flat line should be the result.Now you do the same thing for the output, and you get an FFT that is not flat anymore and you also get a phase curve due to the delay created by your DUT. If you do this for a sufficiently long time, you obtain a gain/phase plot like by the classic way.The classic swept approach is restricted to linear time independent systems. A lot of systems are *not* strictly linear, and Keysight has blown up their top line of VNAs to extract models for (moderate) nonlinear behaviour of DUTs using a harmonic balance approach. This approach seems to be most useful for mobile phone base station transmitters where linearity iss key due to simulataneous multichannel transmissions. The amps are *very* linear, and the PNA-X VNAs help to optimize them to perfection. For really nonlinear stuff like Paramps, Class C stuff, subharmonics, varactor mixers, ... I dont think the harmonic balance approach is useful.When your input is a random signal, you could assume a parametrized nonlinear model of your DUT and fit the parameters so that the measured output signal is best explained.My idea was that this could work better than a HB approach due to more flexibility in the models used.

author: JohnPi
author_rank: Regular Contributor
timestamp: September 04, 2018, 01:17:23 am
content: I checked with a square wave (and added a -q command-line option). It's not as good as a sinusoid.At low frequencies it's nearly identical, but at higher frequencies, the slight mismatch between scope sampling and whole (square wave) cycles leads to signals 'leaking' and therefore not being measured correctly. For example, at 15.8 MHz, the scope samples 1901 full cycles at 31.5 samples/cycle -- the 0.5 non-integer cycle is what causes leakage and misalignment between the scope and input frequency.Code:Sample 124, 15848931.925 Hz, 500 MS/s, 59972 points; 1901 cycles @ 31.5/cycleIn principle there is a benefit in using a square wave since the amplitude of the fundamental sine wave in it is pi/2 higher -- thus improving SNR by 4 dB in theory. However the leakage at higher frequencies makes the overall result worse, and so I likely won't use it.

author: ogden
author_rank: Super Contributor
timestamp: September 04, 2018, 06:43:33 am
content: Quote from: JohnPi on September 04, 2018, 01:17:23 amThank you for clarifying. Then for LCR adapter ad9833 + amp needed besides arduino. Still lot cheaper than Siglent DS1025. Well ... unless it is el-cheapo eBay "DDS generator.Quote from: JohnPi on September 03, 2018, 10:07:28 pmSample reasonable count of cycles (at least one) in the buffer so you can roughly calculate frequency from zero crossings and tune your numerically controlled local oscillator accordingly. After first correlation you will be able to re-calculate NCO frequency very precisely from phase rotation data (if any). This is more or less how communication modems lock onto transmitter frequency.

author: bugi
author_rank: Regular Contributor
timestamp: September 04, 2018, 07:07:12 am
content: Quote from: JohnPi on September 03, 2018, 08:54:49 pmWeird, my DE-5000 does have 10 kHz. After I power it on (at default settings), a single push on 'freq' switches from 1kHz to 10kHz.

author: Gromitt
author_rank: Regular Contributor
timestamp: September 04, 2018, 01:02:32 pm
content: Quote from: drkirkby on September 01, 2018, 11:40:31 pmHow can they be inferior when they are the original. IET DE-5000 was just a rebadge of DER EE DE-5000.DE-6000 is a tweeked DE-5000, it's the same hardware.

author: precaud
author_rank: Frequent Contributor
timestamp: September 04, 2018, 02:07:15 pm
content: Good project. I've put together several of these rigs over the years (hardware and software) and can offer some pointers.: The key to accurate measurement is the de-embedding, fixturing, and repeatability.: De-embedding (aka Open/Short/Load or OSL) is necessary at all freqs.: Fixturing becomes more critical with increasing freq. Above 1MHz the fixturing becomes critical.: Since you mentioned "with a single resistor" I'm guessing you're using the "Series-R" topology with the DUT to ground after it.: Unless you're doing autoranging, and have high-sensitivity inputs, that topology is demanding on DSO dynamic range. An 8 bit DAC is going to be the limiting factor, especially at low Z's and high freqs. This is where swept FRA techniques hold the advantage.: One can fairly easily get good results at middling freqs and Z's. The challenge is accuracy at the extremes.: Ground loops are a killer at low levels (read up on "braid error"). With generator and DSO inputs all ground-referenced, you're guaranteed to have it.: It really helps to have a set of components that have been measured at various freqs on known-accurate impedance meters to compare your results to.Good luck!

author: bugi
author_rank: Regular Contributor
timestamp: September 04, 2018, 02:09:08 pm
content: Quote from: Gromitt on September 04, 2018, 01:02:32 pmIET may have had tighter manufacturing requirements (no missing components, no replaced components, discard any that do not meet some specifications, etc.). DER is now free to sell them out with whatever changes they like, and even the info on this forum already indicates there are indeed units with differences. Whether those differences will make them "out of specs" or "inferior" is something I have not seen any solid information about.

author: Gromitt
author_rank: Regular Contributor
timestamp: September 04, 2018, 02:16:02 pm
content: Quote from: bugi on September 04, 2018, 02:09:08 pmThe are still the same meter manufactured by DER EE (not DER). I don't think they would downgrade it under their own name.IET did not manufacture the IET DE-5000 (or DE-6000), DER EE did.

author: JohnPi
author_rank: Regular Contributor
timestamp: September 04, 2018, 02:39:57 pm
content: Weird, my DE-5000 does have 10 kHz. After I power it on (at default settings), a single push on 'freq' switches from 1kHz to 10kHz.You're correct -- I misremembered.

author: JohnPi
author_rank: Regular Contributor
timestamp: September 04, 2018, 02:51:24 pm
content: Thanks for the pointers.QuoteI intend to do this -- I just got the software in a state where it works well enough to move to those steps. In fact, while I do have nice smooth plots, I have not confirmed that they are accurate.Do you have any examples or photos of a fixture setup that might be suitable ?QuoteYes. I haven't determined what is the best value to use -- it will depend on the DUT. I may need de-embedding for different values; that'll depend on the accuracies I can achieve.QuoteYes, it autoranges. One nice feature of the Rigol is it has arbitrary values for the y-scale. I basically set the y V/div to make the measurement span +/- 3 divs. If the Q isn't too high and levels don't change too much between frequency steps, this works well. In fact the Rigol only uses +/- 100 counts for full screen display, so there is some over range available. Later I'll add a check for over range and rescale if needed. For the 1st frequency measurement, I do it twice -- once to get a good autorange value.On the Rigol I also calculate and send in an arbitrary x-axis value; it rounds to the next (higher) step, and I read back the actual timescale.QuoteI haven't noticed a problem -- not even 60 Hz pickup.QuoteDefinitely. However I'm most interested in the general trend of the responses, I don'tneedexpect better than a few % accuracy. My main use will be for measuring power supply loop gain characteristics and output impedance.

author: precaud
author_rank: Frequent Contributor
timestamp: September 04, 2018, 03:57:32 pm
content: Quote from: JohnPi on September 04, 2018, 02:51:24 pmI'll post a pic of one later. I was going to make several, but ended up finding a set of the Omicron fixtures for pretty cheap and so I use them.QuoteYes, there are interesting tradeoffs that come with the choice of reference resistor value (and Load resistor value, too). The higher the Ref R, the greater the dynamic range between channels is needed for low-Z. For a "one-size-fits-all" fixture I settled on 33 Ohms.QuoteAutoranging comes with its own set of problems. Now the inaccuracies from range switching is part of the equation. It puts you squarely in the territory of real LCR meters with this - various "range resistors" and receiver gain ranges, all with their own freq and level trims, to cover a wide Z range. OSL does not compensate well for this...QuoteI haven't noticed a problem -- not even 60 Hz pickup.You'll see it when you start measuring things below say 100mOhm...QuoteDefinitely. However I'm most interested in the general trend of the responses, I don'tneedexpect better than a few % accuracy.That's easy to do above say 1 Ohm. But below 100mOhm, a couple % is difficult...QuoteFor output impedance I would definitely concentrate on the sub-100mOhm aspect... most regulated power supplies have output Z well below 1 Ohm...

author: ogden
author_rank: Super Contributor
timestamp: September 04, 2018, 04:27:14 pm
content: Quote from: precaud on September 04, 2018, 03:57:32 pmParticular tool shall be considered as RF I-V impedance meter, with all the consequences (of inability to measure extreme Z ranges). Just proper I-V bridge is needed and that's it. Well, maybe two bridges - one optimized for low-Z and another for hi-Z.

author: bugi
author_rank: Regular Contributor
timestamp: September 04, 2018, 05:14:35 pm
content: Quote from: Gromitt on September 04, 2018, 02:16:02 pmWhile DER EE manufactured it for IET, IET could have asked for tighter quality than what DER EE is doing now. How good a reputation DER EE is wanting compared to IET?The missing and changed components in DE-5000 is not about what I (or you or anyone) thinks, it is pretty much a fact, based on what people have found inside in different units. Whether those differences count as "downgrade" or "inferior" is another thing.The first example are the supply input "protection" diodes. That is, imho originally slightly badly designed thing, they could clamp to low enough voltage and to break to (hopefully) short if a battery or DC-input was connected the wrong way, and thus (hopefully) save the rest of circuitry, though still needing a repair for the broken diode. But my unit had no such diode at all for battery, only the unpopulated pads for it, and the DC input side diode had been moved to replace a larger bulk supply capacitor (the spot still having capacitor markings!). The battery diode certainly does not break now, but it won't be saving the rest of the circuitry, either. I think that counts as a minor downgrade; failure result changed from "potentially slightly broken with easy fix" to "totally broken". (The DC input "protection" diode was also changed to a larger one, I'm not sure that was a good idea, either.)The following example is something I don't know if it is a change or was it always so: missing capacitors on supply rails (which has been measured to have quite some ripple without those caps), only unpopulated pads waiting. At least that does not improve anything. So, if that was a change done after IET times, that is likely also a minor downgrade. (Whether that brings it out of spec is something I can not say.)

author: David Hess
author_rank: Super Contributor
timestamp: September 04, 2018, 05:51:56 pm
content: A had some fun a couple months ago investigating ways to provide input protection to 4 wire LCR meter designs without compromising performance.One thing about input protection diodes and circuits is that even if they protect the rest of the instrument, if they fail it is still usually a hard kill unless the user can replace them like with accessible fuses. I find this crop up in poorly designed RF receivers all the time. If the input shunt protection which guards the RF amplifier shorts out due to an overload, the fact that it saved the RF amplifier is irrelevant to the user.

author: JohnPi
author_rank: Regular Contributor
timestamp: September 04, 2018, 06:25:40 pm
content: QuoteI intend to do a 2-D cal -- over frequency and voltage(to account for possible different voltage scaling errors on different ranges); both on a log scale. I need to determine what types of errors the scope introduces when it switches ranges, and when it uses the vernier range. Likely separately on each channel.I'll store the data vs log(f) and log(V) and use 2-D interpolation between points when actually measuring. So that calibration doesn't introduce additional (random) errors, it needs to be performed many times and averaged.

author: ogden
author_rank: Super Contributor
timestamp: September 04, 2018, 06:41:49 pm
content: Quote from: David Hess on September 04, 2018, 05:51:56 pmIf you ignore possibly countless other incidents when protection saved RF amplifier w/o failing/shorting - then maybe yesAnyway repair shops shall take in account difference between repairing protection components compared to frontend amplifier (LNA) repair.

author: MrW0lf
author_rank: Frequent Contributor
timestamp: September 05, 2018, 07:52:03 am
content: Quote from: JohnPi on September 03, 2018, 09:51:04 pmBTW back in the day I did some wild experiments with single-formula (no programming) FRA to work directly in scope software using external signal gen just outputting freq sweep (also no programming). Range was indeed about 30...35dB however some interesting results like measuring general shape of response at100MHz on 25MHz analog BW scopeMain issue with method was that phase plot could not be signed.https://www.eevblog.com/forum/testgear/picoscope-2000/msg1295493/#msg1295493

author: Szybkijanek
author_rank: Contributor
timestamp: August 13, 2020, 10:04:57 pm
content: Hi, I have question, is new 670$ Pintek LCR-900 good choice for home use?

author: rdsi
author_rank: Contributor
timestamp: August 13, 2020, 11:54:23 pm
content: Quote from: Szybkijanek on August 13, 2020, 10:04:57 pmI'm not familiar with that brand but I did pickup aBK Precision 891on ebay for $800 - new open box.This unit operates at DC or from 20 Hz to 300 kHz with 0.05% best accuracy.I thought it was a good compromise between cheap & high end models.I'm not a big fan of BK but it fit my needs & has been accurate/reliable.

author: Szybkijanek
author_rank: Contributor
timestamp: August 14, 2020, 03:42:09 am
content: Thank You, this model is much better.

author: rodpp
author_rank: Frequent Contributor
timestamp: August 14, 2020, 04:20:18 am
content: Look carefully at the specifications, because the accuracy can vary according with the DUT impedance value. Sometimes orders of magnitude.Did you considered used ones? For example the digibridges from genrad. I have the digibridge 1657 an 1689, both are very good and you can find complete manuals with schematics. The 1657 is more limited but less expensive, and the 1689 is much more accurate and flexible in test configurations.

author: Szybkijanek
author_rank: Contributor
timestamp: August 14, 2020, 04:47:04 am
content: I did not consider used ones because I am afraid that it will be damaged.

author: rodpp
author_rank: Frequent Contributor
timestamp: August 14, 2020, 05:22:24 am
content: Yes, that is a valid concern.But for home use, maybe it is part of the fun...Buying used equipment sometimes is the only reasonable way to have good tools for home use. I always choose an used better specified equipment over a new one with less performance at the same price range.Another point is that after the warranty of new equipment expires, it is very hard to fix an eventual problem. While with old ones chances are that you can find full schematics and the problem is easy to fix.But if the equipment use will be other than hobby, it is a different story.