Accuracy of LCR meter? - Page 1
Forum section: electronics / testgear

author: Faringdon
author_rank: Super Contributor
timestamp: June 28, 2022, 02:30:20 pm
content: Hi,Do you agree this LCR meter cannot realistically measure 37uH or so?...because its accuracy is stated as 2% of 2mH = 40uH.LCR meterhttps://www.farnell.com/datasheets/1955257.pdf

author: rs20
author_rank: Super Contributor
timestamp: June 28, 2022, 02:39:47 pm
content: Yeah, I suspect it'd be fairly useless for that, but I think your reasoning is wrong.37uH would get rendered as "0.037" mH, except it would it would be off by up to (2% of 37 uH (negligible; ~ 1uH) PLUS 8 counts (where the least significant digit here is uH, so ~ 8uH)), so anywhere from "0.028" to "0.046" mH would be reported in the case of a nominal 37uH inductor. In other words, about +/- 25% error on the inductance value. So pretty hopeless.

author: Martin72
author_rank: Super Contributor
timestamp: June 29, 2022, 08:59:32 pm
content: Hi,QuoteAccording to the sheet you´ve linked, there is no remark that the 2mH range got 2%.It´s only stated, the BEST accuracy will be 2%, not on which range.Apart from this, 2mH as lowest range makes it useless.It should have 200µH range at least:https://www.amazon.de/Kapazit%C3%A4ts-Induktivit%C3%A4ts-Pr%C3%BCfvorrichtung-Meter-Selbstentladung-Strecken-Anzeige/dp/B07BR2N7GB/ref=asc_df_B07BR2N7GB/?tag=googshopde-21&linkCode=df0&hvadid=266451026830&hvpos=&hvnetw=g&hvrand=7066970650968613726&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9043666&hvtargid=pla-444110103102&th=1My recommendation :Save a little bit more money and buy a DER DE5000.Starting at appx 100 bucks, depending on the accessoires, there´s no better choice for the money, imho.

author: bd139
author_rank: Super Contributor
timestamp: June 29, 2022, 09:17:25 pm
content: Buy Peak LCR45 from CPC. That will measure reliably down to 0.3uH which is outside it’s specified capability. I’ve tested one against a fixture with a signal generator and scope and a 6.5uH inductor was measure at 6.6uH.I wouldn’t buy the DER. There’s no warranty service or calibration options unlike the Peak.

author: Martin72
author_rank: Super Contributor
timestamp: June 29, 2022, 09:29:07 pm
content: Warranty: Who cares about it, when buying ultra-lowcost stuff like DER or peak.Calibration: It´s the same, open and shorted probes.We got LCR40 and LCR45 at work for quick checking, can do a comparison between them and the DER, if it´s interesting for anyone.

author: bd139
author_rank: Super Contributor
timestamp: June 29, 2022, 09:32:51 pm
content: Please do. Interested in results.As for warranty I do. Stuff on the cheap end likes to drop dead.

author: TimFox
author_rank: Super Contributor
timestamp: June 29, 2022, 10:04:51 pm
content: The DER unit is cost-effective. I have checked my unit's calibration against secondary lab standards, and was amazed at the accuracy.You do have to run through the calibration routine with the test connections you intend to use for the measurement, and you do have to be careful not to connect a charged capacitor to the terminals.My only complaint is that if you measure a "capacitor" whose actual reactance at the (high) test frequency is inductive (above SR), it does not return a negative value, so you don't know that it is inductive.You need to use the phase angle measurements to check on the sign of the imaginary component.In doubtful cases, I would prefer a real/imaginary component readfout, but the inexpensive DER does not support that.

author: mawyatt
author_rank: Super Contributor
timestamp: June 29, 2022, 11:38:42 pm
content: 2nd the DE-5000, really good value. Here's a few comparisons we did some time ago with a Tonghui TH2830 lab type LCR meter.Reading/ESR and TH2830 with supplied Kelvin Clips and DE-5000 with supplied short Alligator clips except as noted.Type TH2830 DE-500010uH @100KHz 9.39761/0.1754 9.366/0.13470uH @100KHz 449.188/3.8841 449.8/5.1470uF @100Hz 439.802/0.13115 440.6/0.1100uF @ 1KHz 91.6142/0.43874 91.72/0.431uF @ 1KHz 1.00896/0.0181 1.0097//0.020.1uF @ 100KHz 99.5913nF/0.289 99.52nF/0.282.2nF @ 100KHz 2.18710/11.435 2.193/10.72#12 Wire @ 100KHz 51.123nH/0.00206 43nH/0.00 51nH/0.0 with special custom Kelvin Clips0.1 ohm @ DCR 0.101054 0.111 ohm @ DCR 1.00540 1.0110 ohm @ DCR 9.97630 9.97100 ohm @ DCR 99.7219 99.611K ohm @ DCR 998.001 998.0Judge for yourself how good the DE-5000 behaves!!Best,

author: bicycleguy
author_rank: Frequent Contributor
timestamp: June 30, 2022, 01:36:43 am
content: I'm really liking my Shannon LCR Tweezers.There discussed here:https://www.eevblog.com/forum/testgear/design-a-new-precision-lcr-tweezers/msg3473886/#msg3473886Kind of new, (device and for me), but 3 firmware updates since I bought. I've been to busy to study the specs, but in use it matches my 121GW. Haven't bothered to calibrate it yet. Repeatedly measures a 10uH inductor as 9.966uH.

author: tautech
author_rank: Super Contributor
timestamp: June 30, 2022, 01:49:01 am
content: Quote from: bicycleguy on June 30, 2022, 01:36:43 am100% with you on smart tweezers and been using them for 15 years on all TH and SMD work.Good quality ones and it seems Shannon's are, negate the need for other LCR equipment unless you're chasing high precision in which case you'd be better off with a mains powered bench LCR meter.

author: abdulbadii
author_rank: Frequent Contributor
timestamp: June 30, 2022, 06:41:03 am
content: How SMD C can be known onboard when there often possibility of lowering ohm parallelsneed to separate a pin and so ordinary probe should be used finely anyway

author: bd139
author_rank: Super Contributor
timestamp: June 30, 2022, 06:44:23 am
content: Indeed. To get an accurate impedance measurement of a part it needs to be in a fixture or you're getting an impedance measurement of the network. That might be good enough but it's not good enough for most diagnostics hence why I don't own SMD tweezers. Lifting a leg or the whole SMD part is advisable and you can usually make do without the tweezers then.If you must have tweezers, Peak sell 'em:https://www.peakelec.co.uk/acatalog/smd03m-lcr-and-esr-test-tweezers.html

author: fyl2022
author_rank: Newbie
timestamp: June 30, 2022, 07:39:35 am
content: you may try a benchtop lcr meter, MATRIX LCR METER MCR-5200 looks nice, it has good accuracy and quality, they sell on amazon, here is the buying link:https://www.amazon.com/MATRIX-apacitance-Insulation-Resistance-%EF%BC%8840Hz-200kHz%EF%BC%89/dp/B07ZCJ1319/ref=sr_1_1?crid=GFLDWRR2RHG2&keywords=MCR-5200&qid=1656574710&sprefix=mcr-5200%2Caps%2C665&sr=8-1

author: BravoV
author_rank: Super Contributor
timestamp: June 30, 2022, 11:42:26 am
content: Accuracy for LCR meters that use Cyrustek ES51919 and ES51920 based chip sets are pretty good. Example : DE-5000, MS-5308 or UNI-UT612 and etc.For calibration there was an info shared by other fellow here in this forum ->Quote from: mwb928 on May 15, 2018, 10:20:56 amUsing my cheapo MS-5308 compared with probably 5 digits priced Wayne-Kerr 6440B LCR meter...

author: rs20
author_rank: Super Contributor
timestamp: June 30, 2022, 03:29:22 pm
content: Quote from: Martin72 on June 29, 2022, 08:59:32 pmI... I realize that this is what a literal interpretation of the column title might imply, but surely this is wrong and the column is just poorly labelled. There's no way that ±(2%+8) figure applies to only one range; and that the manufacturer is making absolutely no claim whatsoever about the performance in the other ranges?

author: AVGresponding
author_rank: Super Contributor
timestamp: June 30, 2022, 05:51:19 pm
content: Quote from: rs20 on June 30, 2022, 03:29:22 pmWouldn't surprise me if the accuracy dropped off to 5% or so, and maybe near 10% at the top ranges.As BravoV's post shows, meters from the well known brands like DER, Uni-T, Peak etc are all good enough for a hobbyist. There are always gotchas ofc; high voltage performance can only be realistically tested using high voltages for example, such as for leakage current/breakdown on caps.

author: BravoV
author_rank: Super Contributor
timestamp: June 30, 2022, 06:51:10 pm
content: Quote from: AVGresponding on June 30, 2022, 05:51:19 pmYes, the only limitation using this kind of handheld LCR meter is DC high voltage biased measurement, eg: measure a capacitor at their rated high voltage as its characteristics may be different compared to the low voltage measurement signal generated from the handheld LCR meter as its battery powered. Imo, this is not super uber critical for hobbyist.But for enthusiast, for capacitor leakage measurement, its "relatively" easy with only a DMM with 10M Ohm input and an adjustable DC power supply.Example ->Quick n dirty method to measure cap leakage... and you don't need an expensive DMM like this example, just need the one with 10M Ohm input. It worked very well.

author: ebastler
author_rank: Super Contributor
timestamp: June 30, 2022, 07:37:50 pm
content: Quote from: fyl2022 on June 30, 2022, 07:39:35 amAny chance you are working for the seller? Right, thought so. Thank you for the impartial recommendation.

author: mawyatt
author_rank: Super Contributor
timestamp: June 30, 2022, 07:38:52 pm
content: Monitoring capacitance vs voltage is an interesting experiment to perform with LCR meters. The high K dielectrics used in common ceramic capacitors cause a dramatic reduction in capacitance with applied voltage, aluminum electrolytics also show a capacitance voltage dependance, although tantalums are much better. Generally the "film" types are OK. Monitoring semiconductor diodes is also interesting to see how the junction capacitance varies with applied voltage, these include Schottky, regular signal, rectifier, Zener and transistor junctions.The cost of a lab type LCR meter that supports a wide range of applied DC voltages (or currents) is high, and many of the moderate cost lab type meters without this feature can be "augmented" with a circuit to isolate the DC from the AC measurement and allow accurate measurements in the presence of DC bias. Here's a link to a DIY device for such.https://www.eevblog.com/forum/projects/bias-network-for-lcr-meter/msg4091638/#msg4091638Best,

author: Martin72
author_rank: Super Contributor
timestamp: June 30, 2022, 08:51:26 pm
content: Quote from: rs20 on June 30, 2022, 03:29:22 pmWhat makes you sure to think it isn´t so ?As I´ve read the "specs" I´ve stumbled over the word "BEST".Best means to me that there will be also "normal" and "worst" accuracy - but not shown in this case.2nd pic below shows a snip of the specs from peaktech 3730 lcr-meter, nearly similar.That´s more plausible, there are 2% and 5% accuracy mentioned and when you state only the 2%, it will be the BEST accuracy.(Same on R and C)

author: rs20
author_rank: Super Contributor
timestamp: July 01, 2022, 12:14:11 am
content: OK, I stand corrected, thanks for taking the time to provide evidence. I'm appalled that they think it's OK to present their performance specs like that, but I guess I'm just naive.

author: bd139
author_rank: Super Contributor
timestamp: July 01, 2022, 05:51:39 am
content: Worth pointing out that specifications are always conservative here or open to interpretation because fixture and lead capacitance and inductance is a function of the measurement methodology employed by the user. They may make up a significant portion of the measurement. This is unlike resistance which is only an issue on very low resistance measurements.Ergo it’s better not to worry about a couple of percent and a few counts and work out what the tolerance and device spread of your design is and make sure you window values within that.

author: AVGresponding
author_rank: Super Contributor
timestamp: July 01, 2022, 07:02:50 am
content: Also worth pointing out the laughably wide manufacturing tolerances on some components, notably electrolytic caps which can be as wide as +20/-80%Edit: Might have been -20/+80% that I saw once. Either way, measuring the capacitance there would have limited use, ESR would be the better measurement.

author: bd139
author_rank: Super Contributor
timestamp: July 01, 2022, 07:17:02 am
content: Usually -20% +80%. Unless it's ChongX and then you might as well ignore the label and look at the size of the can and make a finger in the air estimate.

author: mqsaharan
author_rank: Regular Contributor
timestamp: July 01, 2022, 09:29:46 am
content: Quote from: BravoV on June 30, 2022, 11:42:26 amBe careful while calibrating these LCR meters. You need a meter with Hi-Z input impedance. Even a 10M input impedance meter loads down the reference voltages.

author: Martin72
author_rank: Super Contributor
timestamp: July 01, 2022, 09:53:52 pm
content: Quote from: bd139 on July 01, 2022, 05:51:39 amExactly.You won´t design a coil into a circuit with a tolerance under 5% in most of the cases.The AL value of the used core makes it impossible for mass production without cost intensive pre-selections.So tolerances about 20% are not uncommon - Every LCR should handle this..Of course there are some exceptions, e.g. coils for filters to suppress unwanted harmonics.We (company I work for) make most of our used coils and transformers ourselves.And test/adjust them.We got several different LCRs and therefore different values of the same coil.For the most the measuring with one of the LCRs are enough, for other we use resonant test circuits* for adjusting them.Further we use Voltage-Time-Area function** or, with our self build tester, testing coils with large currents up to 200A***..Based on this experiences, I can recommend LCRs building like the DE 5000 for most of the needs of a hobbyist.Martin*) Example: Filter-Coil, Air-Gap adjustment to reach given value 90µH +/- 3µH.Using resonant circuit with additonal cap of 10µF/1%, adjust amplifier to 10Vrms, adjust airgap in such manner, that on 1.64....1.65khz the flowing current gets his minimum value.**) Special case, self satured coils for zero switching, define windings on the coils per feeding in an impulse with high voltage, use math from scope, building integral function for voltage-time-area.***) High power coils for output filters....normal LCRs didn´t have current, only a few mA max, our self build tester can deliver pulse-current up to 200A, adjustable.The circuit based on a µC, some electrolytic caps for the current and a IGBT for switching.L will be calculated based on the formular L= U*t/I (linear current is a must of course)