help with difference between ESR, LCR, and impedance meters

[themadcapper]

pardon the newbie question, but can someone explain to me the difference between an ESR, LCR, and impedance meter. Doesn't an ESR meter also measure impedance? I ask because it seems as if impedance meters seem much less expensive than the various ESR meters available, although I'm not quite understanding the difference. - thanks!

[starfury1]

Re: help with difference between ESR, LCR, and impedance meters

There are a few posts on what ESR is and getting to the finer details it can become somewhat complex
being in mind I am really very much simplifying this

I like to think of "impedance is to AC what resistance is to DC "
Loosely speaking

but ESR is the equivalent of of all (in phase) impeding factors as an equivalent resistance (measured, (really) @ frequency).
(thats putting it way simple and probably not the best of definitions)

ESR is the sum of in-phase AC resistance. It includes resistance of the dielectric, plate material, electrolytic solution, and terminal leads at a particular frequency. ESR acts like a resistor in series with a capacitor (thus the name Equivalent Series Resistance). This resister can cause circuits to fail that look just fine on paper and is often the failure mode of capacitors.

http://wiki.xtronics.com/index.php/Capacitors_and_ESR

In a purely resistive circuit the Voltage and Current are in phase with AC (or DC)

There is a thing that happens with Voltage and Current once you introduce reactive components like capacitor and inductors
you end up with a Phase shift between current and Voltage (90 Deg)
(yes folks they really are different beasts)

you can think of a capacitor and inductor as being the exact inverse opposite of each other.

so the current and voltage will be out of phase.

With a capacitor the current leads the Voltage, An inductor the current lags the voltage. (ICE ELI)

a capacitor is an open circuit to DC but an inductor is a short circuit
(why?, its a piece of wire by any other name, where as a cap is two conductive plates separated by an insulator like air paper mylar whatever)

probably best put by the Wiki

Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal alternating current (AC). Electrical impedance extends the concept of resistance to AC circuits, describing not only the relative magnitudes of the voltage and current, but also the relative phases. In general impedance is a complex quantity "Z" and the term complex impedance may be used interchangeably; the polar form conveniently captures both magnitude and phase characteristics,

http://en.wikipedia.org/wiki/Electrical_impedance

So impedance takes into consideration the phase shift relationship as part of the equation

as I said it can get quite involved

There are posts around here on it with links and also different peoples views and perceptions on it, how they explain or perceive it all which may help understand it all.

To your specific question
I think its a case of horses for courses , not totally sure on that but probably not
I think from memory the ESR meter (depending) is basically an AC (very) low ohms meter where as an impedance meter users a nulling technique to get its measurement
I cannot say this for sure...but them again if they could wouldn't everybody just use one?..

Ok since when a capacitors ESR fails its usually in a big way there are simpler cheaper circuits out there that might do the job...there is a thread on that here in the forum somewhere (think its in the test equipment forum).

HTH

Cheers

[PeteS in CA]

Re: help with difference between ESR, LCR, and impedance meters

Ditto what Starfury said. ESR is resistance only; impedance takes into account ESR and the reactance (X) due to capacitance(s) and inductance(s). Impedance (Z), when stated as a number is always at a specific frequency, as the inductive and capacitive reactances vary with frequency. At the frequency where X(C) = X(L) then Z = ESR.

An LCR meter is able to measure inductance (L), capacitance (C) and resistance (R). Beyond this, LCR meters vary considerable in capability (and price): multiple measurement frequencies; parameters such as ESR, Q, DF ... ability to analyze the impeadance of a network of components.

[starfury1]

Re: help with difference between ESR, LCR, and impedance meters

Thanks PeteS that made it much neater

heres the link to the thread

https://www.badcaps.net/forum/showth...8&page=1&pp=20

Id forgotten about that last one....life's what happens while your making other plans

I have no idea how good or bad any of them are, never build one of the designs

for anyone after Bob Parkers design its probably best to buy EVB pre build and tested one (kits at this point are no longer being produced, )

just check there website, flippers.com appear to have some stock left
(as a kit or pre built)

As I said there are other units out there, and as you probably expect you have the good the bad and the ugly in relation to them.
so there is a "let the buyer beware" cause I am sure there are some shonky ones available too

For Caps its well worth getting or building something to use.

[davmax]

Re: help with difference between ESR, LCR, and impedance meters

ESR meter is also very useful for measuring low value resistors like 0.1 ohm or two in parallel 0.05 ohm.
In fact these low known values are useful for calibrating the ESR meter.

[starfury1]

Re: help with difference between ESR, LCR, and impedance meters

Actually you calibrate Bobs meter with resistors.

[davmax]

Re: help with difference between ESR, LCR, and impedance meters

Yes, I have Bob's meter. All ESR meters should be checked with known values of resistors that are near to the ESR values that you are seeking to measure.

[themadcapper]

Re: help with difference between ESR, LCR, and impedance meters

I just got specs to a "Digital LCR MultiMeter Inductance Meter Tester". Understanding correctly it seems to be able to check resistance at .1ohm resolution, but the lowest ohm reading seems to be in the 2(4)00 ohm range. So I guess that's the real difference, is that an ESR meter can measure under an OHM whereas most multimeters are measuring MUCH MUCH higher ohm levels. Feel free to correct me if I'm wrong in this understanding.

[starfury1]

Re: help with difference between ESR, LCR, and impedance meters

ESR meter
well the way it measured with capacitors is with a low level AC voltage @ frequency (100~150Khz) Roughly speaking.

If you look at spec pdf's for caps, the ESR ..you will find say worst case .02 of an ohm @ 100Khz (thats if I remember the frequencies correctly off hand)
(also sometimes they used a different spec for this )

Due to the fact that a capacitor is essentially and open circuit to DC you can't use a DC type resistance measuring item to do the job even if it can measure lower then an ohm.

Hope that makes sense


Cheers