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ESR meters?
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lagunablue94c
Hello all,
I'm looking to get an ESR meter to help diagnose my broken 2235. I want something thats not going to break the bank, so I have these two kits in mind: Blue Meter LCFesR 3.06 Does anyone have any experience with either of these kits, good or bad? Thanks, Bryan
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Tom Miller <tmiller@...>
I have the Blue meter and like it. I work on a lot of scopes so find it
useful. It only
took about two hours to build it and I put some good leads on it instead of
the
ones that came with it.
However,
The best way to measure ESR is in circuit and with a scope. Just look at
the ripple
and check the specs.
But that doesn't help you until you get your scope working :(.
Tom
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tom jobe <tomjobe@...>
Hi Bryan,
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The ESR meter deal has been discussed over and over again on Tekscopes, so the Tekscopes message archive has lots of ESR talk in it. I own three ESR meters including the Blue ESR Meter. They all work good, but my favorite is the one from Portugal which is just another variation of the famous Bob Parker design, as is the Blue ESR meter. http://clientes.netvisao.pt/greenpal/evb1.htm The Portugal meter comes from a guy who is a treat to do business with, and you supply your own probes that plug into the meter. The Blue meter has soldered in leads that are awful, so you have to change them. As for your 2235 problems, I think you are getting "way" ahead of yourself with all of these complicated assumptions. Your Fluke will check the ripple good enough on the AC range, and it will take all of ten minutes to check both the DC and AC ripple on all of your low voltages. If there is something wrong with the low voltages, the scope is going to do strange things until you fix the problem(s) which will probably just be a few capacitors. I have lots of 22xx scopes, and I like them for learning. You can work on most of the scope while it is running, which you can't do with most scopes. It's like a class room in a box, with excellent documentation as a bonus. Best of luck with your 2235! tom jobe...
----- Original Message -----
From: "lagunablue94c" <bryanlow70@...> To: <TekScopes@...> Sent: Friday, May 20, 2011 9:44 AM Subject: [TekScopes] ESR meters? Hello all, I'm looking to get an ESR meter to help diagnose my broken 2235 <http://tech.groups.yahoo.com/group/TekScopes/message/61954> . I want something thats not going to break the bank, so I have these two kits in mind: Blue Meter <http://www.anatekcorp.com/blueesr.htm> LCFesR 3.06 <http://members.upc.hu/lethanh.hung/LCFESRmero/en/index.htm> Does anyone have any experience with either of these kits, good or bad? Thanks, Bryan
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w2aew
For what it's worth, I just posted a video on YouTube last night that describes a VERY basic analog ESR meter that I built about 5 years ago. I had just used it to find a couple of bad electrolytic caps in an LCD monitor power supply.
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It is certainly NOT a well refined and calibrated instrument that you can buy or build from a various kits, but it can give you a basic relative reading of ESR. I've found it useful, and maybe you will too. I built it after examining many of the schematics and techniques that folks have published on the internet, and then designing the circuit using the ideas that liked and the junk box parts that I had on hand at the time. Here's a link to the video: http://www.youtube.com/watch?v=bmYAgat-sOQ Hope this helps! Alan W2AEW
--- In TekScopes@..., "tom jobe" <tomjobe@...> wrote:
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kevinjohn5889
I recently purchased the EVB ESR meter in kit form. Kit components
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nicely laid out and documented. Highly recommended. Excellent design (identical to Bob Parker's with a few improvements) and packaging and Vitor Manuel is a pleasure to deal with. http://members.ozemail.com.au/~bobpar/esrmeter.htm Kevin Chadwick
----- Original Message -----
From: lagunablue94c <bryanlow70@...> Date: Friday, May 20, 2011 12:44 pm Subject: [TekScopes] ESR meters? Hello all,
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George
Greetings,
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I have a Blue ESR and found that in building there seems to be a slight filn on the board. If doing it again, I would use an pencil eraser on the exposed pads before you solder the parts so to insure good solder flow . good luck, George
--- In TekScopes@..., "tom jobe" <tomjobe@...> wrote:
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Paul Amaranth
I built one of these:
http://members.shaw.ca/swstuff/esrmeter.html I made a minor modification by using a 9V battery and a 7805 regulator; all my other small meters use 9V batteries anyway. Not fancy, but works great. Sometimes, "if it don't read 0, it's bad" is all you need to know. On mine, the meter has a high value of 10 ohms, not the 75-100 he indicates in his writeup. It was well worth the effort to build. -- Paul Amaranth, GCIH | Rochester MI, USA Aurora Group, Inc. | Security, Systems & Software paul@... | Unix & Windows
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John Sehring <wb0eq@...>
There's a little more to the ESR & capacitor story.
A capacitor can be modeled (for out purposes) as a "black box" with two items in series (although it can be done in a more much sophistated way with more than just these elements): #1. A resistor which represents the Equivalent Series (internal) Resistance ESR of the capacitor; it tends to limit the current flow into and out of the capacitor; this can be very important in power supply apps. #2. A capacitor in parallel with a resistor which represents the Leakage Resistance of the capacitor. Because it's in parallel with the actual capacitor element, it is what's responsible for the capacitor losing its charge with time, self discharge. Put #1 and #2 in series, and, voila, our equivalent capacitor circuit. As you might imagine, if you mentally replace the caps in a circuit with their equivalent circuit (#1 & #2 together) and assign values to ESR and R(leakage), the circuit may want to perform quite different than intended, even bizarrely! It can be quite a puzzler. Item #1 is quanified by an ESR tester; ESR which is basically inherent to the battery although it can vary a lot with temperature. It is generally relatively low in value. I see plenty of them on the web. Item #2 varies with the kind of capacitor. The leakage of electrolytic capacitors is called leakage current; it can allow current on the order of milliamps (it varies with capacitance & its voltage rating). The leakage resistance of non-electrolytics is called insulation resistance; it is measured in tens or hundreds of megohms. The latter is is generally much higher although the former. My favorite way to measure capacitor leakage is with a capacitor checker such as the Sprague TO-5, -6 & -6A. These are boat anchor units using tubes. I find them at electronic flea markets and eBay for pretty cheap; they are perfectly serviceable. They also measure capacitance and the power factor of electrolytic caps. Many electrolytic caps showing excessive leakage can be reformed by using a cap checker to put a gradually increasing DC voltage across them & monitoring the leakage current. I limit it to about 10 mA in the beginning to avoid excessive internal heating; as this current falls, I am able to increase the applied voltage, but not exceeding the cap's rated voltage. The process can take 30 minutes or more for caps that have been idle for long periods of time, for the leakage current to settle down at its rated voltage. The manuals for the all these Sprague cap checkers are available for free download on the web; they contain very useful tables of acceptable values for leakage current, leakage resistance & power factor for caps. See for example: http://bama.edebris.com/manuals/sprague/TO-6 Note that the tables of allowable values has changed in the TO-6 vs. TO-6A manuals due to advances in capacitor design; I use the older tables for older caps. --John Sehring WB0EQ/VE6 Okotoks, Alberta, Canada
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Artekmedia <manuals@...>
John et all
A great analysis of what is going on ..with ESR. , The other thing that we all often forget is that most real world capacitors are far from being "ideal". The first variable to add to the equation is that both of the Rs and Rp components in the model are frequency dependent and can change quite dramatically with frequency depending on the capacitor construction and age of the cap. Ideally then we should measure ESR at the frequency of interest say at 60 Hz or 120Hz for a standard mains type simple rectifier power supply filter cap or considerably higher in frequency 50KHz to 1MHz for switch mode supplies. Also especially in polarized caps like electrolytics, Rs and Rp ( and C) can change as a function of the applied DC Component or "bias" in many caps a pure AC measurement of ESR will be different than it would be with say with a DC bias of 50% rated DC voltage for the cap. Which leads me to ponder a more complex ESR meter which would be part sweep generator and part transistor curve tracer giving a family of ESR curves vs frequency and DC bias .....hmmmmmm To come back to earth for a moment the practical message is that most of us are using an ESR meter to find a really gross failed cap easily and not to hand pick an ideal cap for our application. What is important is to know how any given inexpensive ESR meter handles these two variables and how close those variables relate to the actual circuit we are using the cap in. Cheers Dave NR1DX On 5/22/2011 10:08 AM, John Sehring wrote:
-- Dave & Lynn Henderson Manuals@... www.Artekmedia.com PO Box 175 Welch,MN 55089
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John Sehring <wb0eq@...>
I ported my comments on ESR & leakage in caps over the Boatanchors list & this was one response to it. Thought you might be interested. Cross fertilization is good!
================================================================= Folks, John, thanks for the very good capacitor equivalent circuit description. Let me add a little more info. First, some numbers for leakage resistance in plastic film capacitors. I have a megger and can read up to about 500,000 megohms resistance. Paper capacitors, even ones that have never been used, are now all quite leaky, maybe 1-20 megohms. The yellow axial leaded parts that many of us use, and that were sold for a long time by Antique Electronics Supply, usually show a little leakage at 50,000 megohms. Sprague orange drops show no leakage I can measure. The yellow ones work fine; 50,000 megohms is a very large resistance. I mention them and the orange drops just to present information that I have. For example, a 50,000 meg leakage coupling cap feeding a 1 meg grid leak resistor from a 200 v plate circuit would only raise the grid voltage by 200x 1/50,000 or 4 millivolts. Electrolytic capacitors: Leakage for modern aluminum electrolytics is generally specified as no more than 0.03 x C x V, where C is the capacitance in Farads and V the voltage rating. This gives, for example, 0.6 mA for a 47 uF 450 V part. For old or NOS filter caps, I generally am happy to use them if they are well below 5 mA. The ESR of electrolytic caps is actually a major problem in switching power supplies. These caps are the first thing to fail in most such designs, due to self heating cause by ripple current flowing in the ESR. They can get hot enough to boil the water inside them and blow their seals. (Side issue, not BA but you might have some of this gear--used to keep track of your tube stash or BA collection of course...): in the mid-2000s a lot of bad electrolytics were made. They worked inf when new, but not a few years later. The tale I heard is that some guy worked for one of the big Japanese capacitor companies for a while and stole the recipe for the soup that goes inside, and took it to (as the story goes) a Taiwanese company, who then proceeded to use it. Unfortunately, he had stolen only *most* of the recipe, the missing bit being whatever makes them last longer. So if your router, cable modem, or computer video screen [or PC] of about that age has died and you know how to do pc board soldering, look inside at the large electrolytic caps. If their ends are bulging rather than flat or have black goo on them, replace those parts and you may have a working box again. I buy only UCC, Panasonic. or Nichicon eletrolytics for this purpose. If you have an oscilloscope, you can use it to decide whether to keep using the old filter caps in a radio [or other piece of electronic equipment] that doesn't have hum or other filter cap failure symptoms. If you look at the ripple (do use a X10 or, better, a X100 probe so as not to blow up the front end of your scope!) you should see a sawtooth, usually about 20-40 v P-P at the rectifier tube filament. If the sawtooth has spikes at the tops of the teeth, that's a capacitor that is on its way out and should probably be replaced. What you are seeing is the ripple current flowing through the ESR, creating the spikes. FWIW, /scott ========================================================= --John Sehring WB0EQ/VE6 Okotoks, Alberta, Canada
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PA4TIM
I agree with all but the last thing, the spikes are as far as I know the
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result of the ESL, not the ESR. About the leakage. I measure that too. Using a HP high resistance source meter or just with a HV powersupply a box I made with some limmiting resistors and a nA/uA/mA meter I connect to the box. Both methods give same results except when resistance is very high other effect come in play. For instance the grease on your fingers or nicotine/grease/dust on the capacitor. In some cases you measure that instead of the cap. Also when the resistance is very high and the voltage to you often measure static fields instead of resistance. I use a shielded box and guarded cables in that case. That makes a lot of difference. About the orange tantaliums, I never found one leaking but if there was something wrong it was high ESR. (about 2 to 5 ohm and I can measure ESR downto about 50nF. I calibrate my meter with 100nF and agains VNA measurements, so not a D-meter that reads in ESR like most) If that is a problem depends on the function. I measure it just out of curiousity and because I'm a measurement junky ;-) (my lab: http://www.pa4tim.nl/?page_id=2 If I measure caps it is while doing a restauration from gear that can not be powered up before reforming the filter caps. But most times after measuring in the patient and seeing the results bad caps give. Sometimes it is hard to judge. I just am at the final of restoring a Fluke 8500 6,5 digit DMM with a lot of problems. Only problem not solved is the ohms-converter. There were problems that looked like they were caused by caps. the caps (the yellow tubes, silver mica and tantaliums) most times measured , I think, not bad. Capacitance OK, leakage OK but replacing them often solved the problem. One thing I also found out, a cap can show effects that look like (normal) dielectric absorbtion. Sometimes this is much more then wanted and this gives problems you do not measure with a ESR or capacitance meter. This is caused by a rupture in the materrial inside. This is a problem in the circuit but also can dammage your capacitance meter O, also important. Never measure leakage, ESR or capacitance on caps that have not been reformed yet. Just try it. You will see the cap needs some time so the electrolyte can form a fresh oxide layer. When I reform them I apply a limmited current and start with a low voltage, "fill them up" Let them stand for a half hour or so, discharge them over a resistor (all in the same test box :-) ) and every time I increase the voltage upto the voltage it sees in the circuit and most times a bit above this but not near or over the rathed voltage. Also about leakage, an electrolytic cap always has some leakage. But how you know it is to much. One thing I have not "proven" but I have a theory. If I take a good 150 V cap and test it. The HP measures about the same resistance at 10V as at 100V. So that you can recalculate to leakage current. That must be the "standard normal" leakage for that cap. Except as it is riotten as hell. But when I measure a much lower resistance at 100V the cap is probably wrong. But again, I just noticed this a week ago and have not done extended testing. I had kept a box with rotten caps but after the rebuild of my lab I can not find it any more. And I need known bad caps for testing. hmm, I had prommissed myself not to start writing over caps and ESR again :-) and wanted just to add the lines about ESL. So I do not blame you if you did not get to here. Oh stupid me, you did ;-) Fred John Sehring schreef op zo 22-05-2011 om 10:22 [-0700]:
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PA4TIM
There is such a meter. It is called a VNA :-)
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Agilent has a app note about how to make milli-Ohm measurements in shunt mode using a VNA. Fred
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IIRC ESR Meters were the subject of a thread a few years ago in this forum. They are quite useful for many things. I have the Dick Smith meter that pretty much is the standard that most of the newer ones used as a model. It is a brilliant design with an excellent user interface.
From: lagunablue94c Hello all,
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ehsjr
John Sehring and Fred PA4TIM wrote:
_Nice_ posts on ESR & caps - thanks! Ed
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