How to measure ESR using LCR for electrolytic capacitor at 100KHz - Page 1
Forum section: electronics / beginners

author: zyuan
author_rank: Newbie
timestamp: June 16, 2024, 08:53:29 am
content: Hi,I am using a LCR meter to measure the electrolytic capacitors used in SMPS at 100 KHz, but I am not certain whether the ESR values on the LCR meter is accurate or not.The ESR is usually a secondary parameters of the capacitance measurement. However, the LCR meter cannot measure the capacitance of e.g. 1000uF capacitor, at 100 KHz, only showing a negative capacitance vaule, but it does show a ESR value. My question is whether such ESR displayed on my LCR meter is still a correct value, even the capacitance at such frequency is meaningless.if the ESR value in such circumstance can still be trusted, then how about other secondary parameters, such like X, D, Q and θ?Thank you very much in advance.

author: wraper
author_rank: Unknown
timestamp: June 16, 2024, 08:59:37 am
content: Set it to 100kHz resistance mode if meter is unable to measure it due to high capacitance. Or it may actually be doing something like that automatically depending on the device.

author: mawyatt
author_rank: Super Contributor
timestamp: June 16, 2024, 04:19:49 pm
content: Not sure what LCR meter you are using, and if you've set things up properly.At 100KHz a 1000uF capacitor has 1.59 milli-ohms reactance, that will be a difficult measurement for even the best meters, and the result of an actual capacitor will likely be dominated by the ESR or series resistance.If you plot the impedance of the capacitor vs frequency you'll see a decreasing Z with increasing F and will "bottom out" when the cap becomes series resonate with its ESL and the result at this frequency is the capacitor ESR.Here you can find some examples.https://www.eevblog.com/forum/testgear/lcr-meter-plot-software/For accurate results with leaded capacitors use a quality leaded fixture (TH26048A) and zero calibrated with a proper shunt as shown. Trim the capacitor leads to reduce the ESL and ESR.Quality Kelvin Clips (TH26011CS) as shown can give good results with leaded components, but we've had better results with the above leaded fixture.Best,

author: mawyatt
author_rank: Super Contributor
timestamp: June 17, 2024, 05:48:17 pm
content: Here's some examples of 1000uF Capacitors. These were measured with a Hioki IM3536 LCR meter and Tonghui TH26011CS Kelvin Clips, as leads on Polymer caps were too short for the TH26048A fixture.The 1000uF 16V is a Beryl RC(M) Electrolytic type, the 1000uF 6.3V Polymers are EPZ40 8m-ohm and PC 7m-ohm types. PC has larger diameter case (8mm vs 6mm).Best,

author: TimFox
author_rank: Super Contributor
timestamp: June 17, 2024, 05:56:36 pm
content: Your graphs show a large frequency range whereR(f) is close to constant.How much of that is due to the uncorrected part of the test-lead parasitic resistance, and how much of that is due to the internal resistance of the capacitor package (which is wet for traditional electrolytics) in series with the inherent capacitance across the formed dielectric?

author: mawyatt
author_rank: Super Contributor
timestamp: June 17, 2024, 06:22:30 pm
content: The test leads (Kelvin) were carefully calibrated out with a Short/Open and 1 Meter cable length compensation after allowing the LCR meter to stabilize, so this is the actual capacitor behavior.Both the Polymer types measured spot on spec-wise for the ESR at 100KHz to 300KHz where they are intended to be used with less than 8 and 7 milli-ohms.Below we've shown just the ESR of each cap, and one can see how much better the Polymer types are wrt to ESR.Best,