Measure capacitor ESR with any LCR meter? - Page 1
Forum section: electronics / projects

author: kc1980
author_rank: Regular Contributor
timestamp: July 01, 2010, 05:19:46 pm
content: Can capacitor ESR be reliably measured with any LCR meter? One would think that THAT is exactly what the LCR meter is designed to do, but there are other factors to consider (e.g. frequency).

author: Zad
author_rank: Super Contributor
timestamp: July 01, 2010, 06:15:47 pm
content: I think it very much depends on the meter. Some meters are true L/C/R meters only, are very crude and only measure charge/discharge time or oscillation frequency in a simple circuit, others pass an AC voltage across the device under test and measure the phase and magnitude of the current. That makes it simple to derive the purely capacitive and resistive components.As you say though, that is just at one frequency, and both R and C values can change massively with frequency. A cap that looks fine at 100kHz may degrade horribly at 1MHz. Ideally you want to be able to sweep the values, but then you start getting into the realm of scalar and vector network analysers.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 01, 2010, 07:32:00 pm
content: I have read somewhere that if you have a signal generator, oscilloscope, and a known (low value) resistor, it is very easy to measure the ESR. Make a voltage divider out of the capacitor and resistor, set the frequency high enough that capacitive reactance is negligible, then measure the voltages.

author: ThunderSqueak
author_rank: Unknown
timestamp: July 01, 2010, 09:46:41 pm
content: Quote from: NiHaoMike on July 01, 2010, 07:32:00 pmhttp://octopus.freeyellow.com/99.htmlSomething like that?

author: Pyr0Beast
author_rank: Contributor
timestamp: July 08, 2010, 11:00:26 am
content: Quote from: kc1980 on July 01, 2010, 05:19:46 pmNo.LCR meter measures inductance, capacitance and resistance, but not ESR of capacitor.You have ESR meter for that.

author: EEVblog
author_rank: Unknown
timestamp: July 13, 2010, 10:12:24 pm
content: Quote from: Pyr0Beast on July 08, 2010, 11:00:26 amActually, many of them do. The Extech LCR meter for example does.It displays ESR on the secondary display.But only at 10KHz.Dedicated ESR meters are better if you are doing this sort of work though.Dave.

author: smpowell
author_rank: Contributor
timestamp: July 25, 2010, 01:58:53 am
content: Quote from: NiHaoMike on July 01, 2010, 07:32:00 pmIf you already have a function generator, look at:http://octopus.freeyellow.com/esr.htmlfirst.My other page athttp://octopus.freeyellow.com/99.htmlincludes the details about making a simplesquare wave generator in case you don't want to use a separate function generator.I'm probably going to simplify the 555 schematic on 99.html pretty soon as the old one is a bit more complicatedthan it needs to be.

author: TechGuy
author_rank: Regular Contributor
timestamp: August 02, 2010, 03:03:28 am
content: Quote from: kc1980 on July 01, 2010, 05:19:46 pmThe Sencore LC103 has ESR measurements. The LC103 also provides a programmable input voltage so you can measure ESR, leakage, etc while the cap is at operational voltage. Many LCR meters make measurements at low voltage which don't tell the full story about a caps performance, Leakage and ESR are typically much higher on bad caps when they are fully charged.http://www.sencore.com/products/general-test-measurement-equipment/75The only anonyance is that you have to press and hold a button while it performs a measurement. This makes it hard to measure a component that you can't attach probes without holding the probes in two hands (ie Surface mount devices or in-circuit radial caps).