Capacitor ESR & Low Ohm Meter

[sidecar]

Hy All,

in order to solve ESR trouble regarding old caps installed on my AR10 & AR5, i've found this site where an instrument is sold at a very affordable cost. http://www.capacitorlab.com/esr-meter/index.htm

Your opinion?

Rgds

[Carlspeak]

I'm skeptical of the matrix printed on the front of the meter. It says those are average ohm values for capacitors. I don't know how they got that info. The ESR can vary greatly depending on the type of cap (i.e. NPE vs film, vs others).

Hopefully the ohms readout works well. however, I wouldn't hold that matrix as gospel.

[soundminded]

Hy All,

in order to solve ESR trouble regarding old caps installed on my AR10 & AR5, i've found this site where an instrument is sold at a very affordable cost. http://www.capacitorlab.com/esr-meter/index.htm

Your opinion?

Rgds

I don't know how useful this meter is but the review stinks....IMO of course. It leaves much out, some of what it says is plain wrong.

"it is rare to see failure in capacitors below 330uf. "

Tell that to anyone who has to replace the 4uf and 6uf caps in an AR2ax or rip an old KLH model 6 apart to replace the 8 uf cap. The review doesn't tell us the principle or operating parameters of the meter, it doesn't tell us its range of capacitor values it will test, especially important to us on the low end of values. We can only surmise how it might operate from the principles on which a capacitor works. For a capacitor: Ztotal = R + Xc where Z is the complex impedence, R the resistance (in this case hopefully only the ESR) and Xc the reactive component which for a capacitor is 1/j*2pi*f*C where f is the frequency and C is the capacitance. To measure just the resistive component the test must be at a high enough frequency where the reactive impedence is negligable taking into consideration the value of the capacitor being tested. So for very small values of capacitors such as is typically used in crossover networks and especially in interstage coupling circuits of amplifiers the frequency should be very high.

Making precision measurements of resistance especially at low resistance values is usually done by balancing a Wheatstone bridge where the tested element is one leg of the bridge. When the bridge is in perfect balance, the resistance of the balancing resistor in the bridge is the accurate value of the tested element. It isn't clear if this is the principle this works on. In measuring very low value resistance the leads should have terminals that are absolutely clean (use alcohol), make excellent contact (alligator clips would be much better than test leads), be of low resistance themselves (short and heavy gage) and be attached as close to the body of the capacitor as possible. Even an invisible thin film of oil from your fingers can affect the measurements.

If the only purpose of the resistor is to discharge the capacitor (a bleeder resistor), you can use any resistor you want if it is low enough in value and high enough wattage. A 50 cent 20 watt resistor from Parts Express will do just fine. I usually use a screwdriver or a pair of pliers, the worst you will usually get is a small spark if the cap has been left charged to a high voltage. BTW, if you do use a resistor, do not touch the capacitor terminals with your fingers until it is discharged or you could get a shock. For a tube power supply cap this could be around 400 volts or more if it had no bleeder resistor or the bleeder was open.

You still need a capacitance meter (often found now on many digital multimeters but not usable above about 20 mfd) and this meter will not alert you to failure due to breakdown of the dielectric resulting in internal arcing when voltage gets too high but is still below the capacitor's rating. Therefor a capacitor that tests good at 1.5 volts or 9 volts may still be defective. This is true for crossover caps and especially for caps in vacuum tube circuits where they see the high DC bias voltates across them. Frankly, I think a good capacitor meter is a much more useful tool and having to choose between them, I'd take the capacitor meter any day.

[Carlspeak]

Here's one you might want to consider buying outright.

http://www.mcmconnect.com/tenma/product/72...%20and%20Meters

BTW, this thread belongs down in the ' other speakers and electronics' catagory.

[Rlowe]

I'm skeptical of the matrix printed on the front of the meter. It says those are average ohm values for capacitors. I don't know how they got that info. The ESR can vary greatly depending on the type of cap (i.e. NPE vs film, vs others).

Hopefully the ohms readout works well. however, I wouldn't hold that matrix as gospel.

The following "link" (with original circuit) to the MkII model may help the technically minded appreciate the design purpose of this meter.

I think his main aim, was to make a device that gave a GO/NO-Go test of "Polar" Electrolytics in TV fly-back circuits for SERVICE TECHNICIANS. I do NOT think he had intended it to cover Audio Crossover caps, ie- Non Polar Electrolytics (NPE) OR Non Polar Polypropolyne caps.

Bob Parker's original construction notes (with circuit) can be viewed at the following location,

http://members.ozemail.com.au/~bobpar/k7214.pdf

SEE - Page 1 Column 1, paragraph 2

“The ESR meter allowed SERVICE TECHNICIANS technicians to quickly and easily identify defective electrolytic capacitors while they were still, in circuit. It measures a characteristic of electrolytic capacitors which is very important: the “equivalent series resistance” or ESR”

SEE also Page2 Column 1 – the 5th full paragraph. (Comment on likely uses)

SEE also Page 6 Highlighted box (Comment on matrix table on front)

Hope this helps.

[soundminded]

The following "link" (with original circuit) to the MkII model may help the technically minded appreciate the design purpose of this meter.

I think his main aim, was to make a device that gave a GO/NO-Go test of "Polar" Electrolytics in TV fly-back circuits for SERVICE TECHNICIANS. I do NOT think he had intended it to cover Audio Crossover caps, ie- Non Polar Electrolytics (NPE) OR Non Polar Polypropolyne caps.

Bob Parker's original construction notes (with circuit) can be viewed at the following location,

http://members.ozemail.com.au/~bobpar/k7214.pdf

SEE - Page 1 Column 1, paragraph 2

“The ESR meter allowed SERVICE TECHNICIANS technicians to quickly and easily identify defective electrolytic capacitors while they were still, in circuit. It measures a characteristic of electrolytic capacitors which is very important: the “equivalent series resistance” or ESR”

SEE also Page2 Column 1 – the 5th full paragraph. (Comment on likely uses)

SEE also Page 6 Highlighted box (Comment on matrix table on front)

Hope this helps.

I read the theory behind the test instrument and it is interesting. The reference capacitor and differential op amp are the sutstitute for the Wheatstone bridge I described in my previous posting. The meter in effect measures how far out of balance the bridge or comparitor is. The meter movement looks like one of those cheap jobs Lafayette Radio and Radio Shack once sold a long time ago as an analog multimeter for around $16.

I think the theory fails to take into account at least two factors which affect ESR. One is that ESR can vary with voltage so the measurement you make at less than 100 mv may not be valid at operational voltages. Also at pointed out ESR drifts with temperature but in failure modes it isn't clear that it can't rise with temperature as well as fall. I think generally for capacitors used in loudspeaker crossover networks, capacitor failure will exhibit many failure modes simultaneously, especially a change in capacitance value. While this meter may be useful in checking out large power supply electrolytics, I wonder how useful it is for those who restore or build loudspeaker systems, even as professionals.

But worse I think is the obsession with ESR and capacitors. The main advantage more expensive capicators like polys offer I think is longevity, not usable performance. Given their sometimes high cost and that many of us provide the sweat equity ourselves when they need replacing those expensive caps don't seem to me like a very good investment. In comparison to the DC resistance of series chokes and voice coils themselves, even speaker wire, the differences between the cheapest and most expensive types seem insignificant. And with loudspeakers like ARs where there is a series resistor in the form of a 16 ohm level potentiometer usually advanced at least part way, buying an expensive capacitor to save a few tenths of an ohm seem ludicrous. Perhaps only in the case of 4 ohm tweeters where a capacitor is the only element in series with the tweeter is it conceivable that there could be any audible difference and then only minor and easily compensatable by use of equalization.

[Tekker]

This site provides a comparrison to these type devices: http://www.anatekcorp.com/testequipment/esrcompar.htm

They also sell them, but their literature seems pretty honest and helpful. Anyway I bought the Blue device kit and put it together in about an hour. It's handy for quick checks in ckt, but not always. I had to disconnect one side to check my AR3a caps, and as was said earlier, it doesn't measure capacitance, just ESR. Low voltage caps always measure pretty high. It's pretty much an AC ohm meter.

Bill

[sidecar]

This site provides a comparrison to these type devices: http://www.anatekcorp.com/testequipment/esrcompar.htm

They also sell them, but their literature seems pretty honest and helpful. Anyway I bought the Blue device kit and put it together in about an hour. It's handy for quick checks in ckt, but not always. I had to disconnect one side to check my AR3a caps, and as was said earlier, it doesn't measure capacitance, just ESR. Low voltage caps always measure pretty high. It's pretty much an AC ohm meter.

Bill

Hi All,

tanks for reply and suggestions. Fortunately I've found a professional equipment in my facility ( I'm working in an aeronautical company) and just today i've check the caps and only two had too much ESR, about 1 Ohm. The others are under 0.1 Ohm.

Rgds,

Claudio

[Steven L. Bender]

Hy All,

in order to solve ESR trouble regarding old caps installed on my AR10 & AR5, i've found this site where an instrument is sold at a very affordable cost. http://www.capacitorlab.com/esr-meter/index.htm

Your opinion?

Rgds

Well ESR meters are neat little helpers that perform a useful task given the number of 'lytic caps present in audio and other equipment - every day. It is somewhat similar to but more dedicated to its task than a multi-meter or DMM. I've owned two ESR Meters for gawd knows how many years! I have the (probably) earliest version of the Bob Parker Digital ESR Meter, which circuitry-wise is probably very much like the later EVB and Blue Meters, except mine has been kicked around and dropped hundreds of times. Remarkably, it has always worked really well for perhaps the last twenty years, but now it gets a bit inconsistent, so definitely its time to change the clip leads (again)!

I also have the Cap Wizard with the analog meter somewhere, but since it went totally haywire about ten or twelve years back, while its manual and schematic are in hiding, so the Cap Wizard meter is wrapped in a plastic bag, awaiting discovery by some future Anthropologist, who will wonder at this weird, malfunctioning, obsolete analog device, long after I'm worm food.

Given that the digital unit was always easier to use, I keep the old digital unit near and rather close to any projects that I'm working on, along with two or three of my Fluke DMM's and assorted Weller soldering stations and soldering irons.

-Steven

[dynaco_dan]

Hy All,

in order to solve ESR trouble regarding old caps installed on my AR10 & AR5, i've found this site where an instrument is sold at a very affordable cost. http://www.capacitorlab.com/esr-meter/index.htm

Your opinion?

Rgds

Hi there

I read all the threads, including today's.

Unless you are a techie, would it not have been, easier and cheaper, to just replace the caps due to their age.

To buy the complete test meter is over $100.00, if you are not a service tech, will you need it for future testing?

Just a thought for today.