ESR and LCR meters - Just get both?

[Keken]

I keep reading about ESR and LCR meters for capacitors. From reading the forums and my own google searching, it's better to get both?

Going to check capacitors on a computer power supply.

[mij59]

Hi,

The ESR function is used to check for bad cap's.
Most LCR meters will have a ESR function.

You could search on eBay, e.g. like this.
http://www.ebay.nl/itm/New-DER-EE-DE-5000-High-Accuracy-Handheld-LCR-Meter-from-Japan-/121401830791?pt=LH_DefaultDomain_0&hash=item1c441ced87&_uhb=1

[Paul Moir]

If you can swing it a DE-5000 is a great LCR meter, which also does an excellent job of measuring ESR.  So if you are in the market for an LCR anyway I would skip a separate ESR meter.

While a DMM can measure resistance accurately enough for most purposes, their capacitance ranges are annoyingly limited.  That is to say, the capacitances you want to measure are often outside their range.  Very few DMMs do inductance and none do it well.

EDIT:  Reviewing your previous posts, you're into repairing a computer power supply.  If you think you'll mostly be doing repair work, an ESR meter will be much more useful than a LCR meter because you can get one with input protection for durability, while I doubt you would ever need a LCR meter.  However if you're interested in electronics (and can discharge your capacitors), than a LCR meter is the way to go.

[Keken]

Thanks for the reply mij59 and Paul

I'm still learning about all of this.
---------------------------
So capacitance and inductance on a capacitor.

Is that what I'm checking for when looking for bad caps? (other than the bulging and spewing stuff)

Which meter checks that?

Am I right to say an ESR meter only checks capacitance?
A higher end LCR meter can check for both capacitance and inductance?

Or am I way off on all this? 

[Paul Moir]

Don't worry about the inductance of a capacitor.  That's not important (yet!).

If you're just checking an electrolytic capacitor to see if it's healthy, ESR is what you want to measure.  It will go up before bulging and spewing occur.  More to the point, many circuits will malfunction with a capacitor with high ESR even before bulging and spewing occur.  Measuring capacitance will not actually show this (capacitance in an electrolytic capacitor will very often go up with age, so it's not a good indication of health.)

On the other hand, if you have an interest in electronic design rather than repair, a LCR meter is a worthwhile investment since you'll likely want to measure inductance (L) and capacitance (C) in the future.  So the extra money and precautions you'll have to take for a LCR meter is warranted. 

(Apologies to those who know more about this.  I think it's wise to avoid dissipation factor right now...)

[AG6QR]

Am I right to say an ESR meter only checks capacitance?

No, an ESR meter doesn't measure capacitance at all.  It measures Effective Series Resistance (ESR) of a capacitor, without checking its capacitance value.  A real-world capacitor behaves like a perfect capacitor with some resistance in series (plus with some resistance in parallel, and some inductance, but we ignore that for now). 

An ESR meter measures low resistances, using a high frequency, low voltage AC signal.  At the high frequency, the ideal capacitor ought to be very nearly a short circuit.  But the real capacitor will have some effective resistance in series, and that's what the ESR meter measures.

When an electrolytic capacitor dries up, its effective series resistance goes up.  As this resistance goes up, if the capacitor is subject to ripple, that resistance causes heating, and the heating causes the electrolyte to dry up faster.  This usually results in a "death spiral", where the ESR fairly quickly goes from low to very high.

A service technician's ESR meter isn't a very high precision instrument.  It's basically a binary tool that's intended to help you separate bad capacitors from good ones.  That's exactly what a repair technician needs to know.  Another aspect of it is that it uses a low voltage signal, low enough to avoid turning on semiconductor junctions.  That way, it can be used to test capacitors in circuit, usually.  It will be fooled by multiple capacitors in parallel, or by a capacitor in parallel with a low value resistor (capacitors are sometimes found in parallel with each other, but capacitors are rarely found in parallel with low value resistors in practice).  But as long as the capacitor is surrounded by semiconductors and/or resistors that are much higher value than the expected ESR, the meter can be used without desoldering the capacitors from their circuits.

A higher end LCR meter can check for both capacitance and inductance?

The L stands for inductance (don't ask me why), C for capacitance, and R for resistance.  An LCR meter measures inductance, capacitance, and resistance. 

[mariush]

There are some ESR meters that can also measure capacitance, for example I have this one from Radiodevices.ru but a version with a different lcd screen : https://translate.google.com/translate?sl=auto&tl=en&js=y&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Fwww.radiodevices.ru%2Fesr%2Fesr4.htm&edit-text=&act=url

If you want one from the designer of that meter, you can contact him on Badcaps.net, his username is RusMike there.

There are some cheap esr meter on eBay, they work reasonably well.  Like AG6QR says, they're not precision instruments, a LCR meter will measure ESR and other parameters much better and more accurately, but you don't need super precision to know if a capacitor is bad or not.

Here's some that should be fine:

http://www.ebay.com/itm/Mega328-LCD-Transistor-Tester-Capacitance-ESR-Meter-Diode-Triode-MOS-NPN-LCR-T3-/171380993981?pt=LH_DefaultDomain_0&hash=item27e71a6fbd

http://www.ebay.com/itm/M168-DIY-Kit-Capacitance-ESR-Inductance-Resistor-LC-Meter-Tester-NPN-PNP-Mosfet-/301217764100?pt=LH_DefaultDomain_2&hash=item4621fa5304
http://www.ebay.com/itm/M168-DIY-Kit-Capacitance-ESR-Inductance-LC-Resistor-Meter-Tester-NPN-PNP-Mosfet-/390866222152?pt=LH_DefaultDomain_2&hash=item5b01713c48

Lots of sellers for these: http://www.ebay.com/sch/i.html?_sacat=0&_from=R40&_nkw=esr+meter&_sop=15

If you get this it should leave you with some budget to get a multimeter for general use.

[Keken]

As of now I'm just a hobbyist, repairing would be my primary focus at the moment. I'm trying not to spend a ton of money. Other than that I am enjoying learning about this type of stuff.

Thanks for the info everyone!

I'll be looking up the links you posted tomorrow mariush.

Currently tired from reading and researching. I'm sure I'll have dreams about all of this tonight.

[jay]

There are some ESR meters that can also measure capacitance, for example I have this one from Radiodevices.ru but a version with a different lcd screen

Wouldn't it make more sense to call those ESR and capacitance meters then? At least in the simple mind of a beginner ESR meter is something that measures ESR.

[David Hess]

If you get an LCR meter or impedance bridge which measures D (dissipation), then you do not need an ESR meter.  Since dissipation for a given type of capacitor is well specified, it is a better measurement of health anyway.  ESR meters have the advantage of being cheap to implement and sufficient in less demanding applications.

[Richard Head]

ESR = Equivalent series resistance, not effective series resistance.

[kripton2035]

esr meters are great for finding bad caps in circuit and most of the time protect the instrument by discharging the capacitor before...
so for repair work an esr meter is an invaluable tool.
check my esr repository (web link below) to have more than you can think of ...

an lcr meter is a precision instrument for measuring inductances ,capacitors, and resistors.
it measures esr, but better out of the circuit, and does NOT support any kind of surcharge.
actually the DER EE De-5000 is a good choice for hobbyist around $80
you can also find a quantity of links to lcr meters on my lcr meter repository