BEC Posted March 18, 2004 Share Posted March 18, 2004 I just got my new B&K Precision Model 885 LCR/ESR and Impedance Meter. Looking for something to try it out on, I spotted some inductors. For those who might be conversant with these numbers, this took only a couple of minutes. The 885 is a nice instrument. Edit: See new test numbers on a post for 3/19/04, The instrument was not calibrated properly during this test. Bob New 2.5 mH iron core inductor built to Klipsch specs. Inductance 2.490 mH DCR 0.284 ohms Q 13.36 ESR 1.170 ohms Z 15.71 ohms Phase 85.75 degrees New Solen 2.4 mH air core inductor 14 awg. Inductance 2.406 mH DCR 0.458 ohms Q 17.04 ESR 0.883 ohms Z 15.14 ohms Phase 87.35 degrees New Parts Express 2.5 mH air core inductor 14 awg. Inductance 2.468 mH DCR 0.478 ohms Q 22.99 ESR 0.633 ohms Z 15.51 ohms Phase 87.6 degrees Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted March 18, 2004 Author Share Posted March 18, 2004 That was so much fun, I thought I might do a couple of caps. New GE oil filled oval can 3 uF Capacitance 2.921 uF D 0.000 ESR 0.018 ohms Z 54.47 ohms Phase -89.98 degrees Solen Fast Cap 3 uF Capacitance 2.947 uF D 0.000 ESR 0.010 ohms Z 54.00 ohms Phase -89.99 degrees New GE oil filled oval can cap 2 uF Capacitance 1.948 uF D 0.000 ESR 0.023 ohms Z 80.19 ohms Phase -89.98 degrees For the one of two of you whose eyes have not yet glazed over from the numbers, here is where it gets interesting. 2 uF Oil filled can cap from my 1979 Lascala Type AA crossover. Capacitance 1.920 uF D 0.914 ESR 75.9 ohms Z 112.3 ohms Phase -47.37 degrees Bob Quote Link to comment Share on other sites More sharing options...
STL Posted March 19, 2004 Share Posted March 19, 2004 So are you saying the old 1979 cap is something special or that it has "worn out" over time? I suspect the latter... Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 19, 2004 Share Posted March 19, 2004 Bob, What is the test frequency of your instruement? 1 KHz is the usual frequency but my measurements don't jive with yours? My old GR 1608a measures a Solen 2.4 mH inductor of #14 wire at 1 KHz like this: On one range: 2.399 mH, Q=24.5 The other range: 2.402 mHy, Q=25.0 This computes to an equivalent sereis R of about: .594 Ohms. ......................... The DCR= .376 Ohms (Solen claims DCR=.360 Ohms). ......................... All this was through test leads measuring about .03 Ohms and 1.26 MicroHenrys ......................... What do you think is giving the Parts Express inductor a higher Q then the Solen? Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 19, 2004 Author Share Posted March 19, 2004 STL I would say the old 2 uF cap is bad. Its capacitance still looks good but the other tests show its age. Bob Quote Link to comment Share on other sites More sharing options...
BEC Posted March 19, 2004 Author Share Posted March 19, 2004 Al, I was using 1 khz for the tests. The meter has 100 hz, 120 hz, 1 khz and 10 khz avaiable. I can't come up with a good reason for the higher Q on the Parts express inductor. The two coils (Solen and Parts Express) are very similar in construction. I need to test the other Parts Express 2.5 mH inductor that I have to compare. I did notice an interesting thing while testing the air core inductors. They are very sensitive to objects close to them. A screw in my wooden work table will slightly affect the values read if the inductor is placed close to it. The iron core variety seems totaly immune to that. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 19, 2004 Share Posted March 19, 2004 Bob, I was revising my earlier post just as you replied to it. Take another look at it. I added exact measurements. Al K. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 19, 2004 Share Posted March 19, 2004 Bob, I suspect that your test leads are too small. For measuring this sort of stuff you need big brutes! The ones I am using are really not big enough and are several lengths (3 I think) of 1/8 inch wide braid shoved inside fish aquirium air hose. Someday I am going to make up a real set of brusers! Try connecting the coil leads diretly to the test posts of the instrument. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 19, 2004 Author Share Posted March 19, 2004 Al, I am using the 4 wire Kelvin leads for the B&K 885. All test lead effect is calibrated out. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 19, 2004 Share Posted March 19, 2004 Bob, The difference between our measurements on the Solen inductor bothers me. Your instrument is new and mine is quite old. My measurements always seem to "jive" between ranges and measurement methods which gives me faith in the old thing, but it has never been formally "calibrated". I would like to resolve the difference. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 19, 2004 Author Share Posted March 19, 2004 Al, I just got back in for the day, A bit later I will take the measurements on the Solen inductor again and I also have another one I can take a look at. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 19, 2004 Share Posted March 19, 2004 Bob, Run a test on that same inductor withOUT the fancy test fixture. Connect the coil directly to the instrument. I got a huntch that's what is causing the difference. I doubt if that fixture was designed to test big stuff like this. Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 19, 2004 Author Share Posted March 19, 2004 Al, I discovered something that I did wrong during the first test. Should have read the manual more carefully. I changed the frequency a few times during the test to see the effect of the different frequencies. I missed the part in the manual about having to let it recalibrate after each frequency change. This should give you a bit of confidence in your LCR bridge. I think we are a lot closer now. Bob New 2.5 mH iron core inductor built to Klipsch specs. Inductance 2.496 mH DCR 0.279 ohms Q 13.29 ESR 1.179 ohms Z 15.73 ohms Phase 85.69 degrees New Solen 2.4 mH air core inductor 14 awg. Inductance 2.407 mH DCR 0.370 ohms Q 25.30 ESR 0.597 ohms Z 15.13 ohms Phase 87.73 degrees New Parts Express 2.5 mH air core inductor 14 awg. Inductance 2.464 mH DCR 0.403 ohms Q 24.96 ESR 0.620 ohms Z 15.49 ohms Phase 87.70 degrees Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 19, 2004 Share Posted March 19, 2004 Bob, That's what I wanted to hear.. I feal a lot better now! Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 19, 2004 Author Share Posted March 19, 2004 Al, Sorry I kept you up in the air so long over those numbers. I had to go out of town today and spent hours thinking about what could be so different between the Solen and the amost physically identical Parts Express air core coil. Decided that either I missed something or the new meter had to go back. Turns out that a five minute read through the manual let me know what had to have happened. No problem with the cap numbers above though. I had just calibrated before that test and was not playing with frequency during the test. The cap numbers should be good. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 20, 2004 Share Posted March 20, 2004 Bob, I didn't try to duplicate the cap numbers becasue I didn't have exact equivalents to compare. They looked ok anyhow. The Solen polypropylene having a D of 000 is a problem I run into with the Hovland Musicaps. Their loss is just too low to measure! My DQ dial just goes to the "infinite" setting! I guess this confirms the old saying "If all else fails, read the manual"! BTW: My old General Radio 1608-A lives on.... 8^) AL K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 20, 2004 Author Share Posted March 20, 2004 Al, You are lucky on your GR 1608A working well. I have one also and mine needs help but is probably not worth fixing. I used one of those (or similar GR bridge) in the Air Force back in the 60's. State of the art at that time. When I found that there was a hand held device that could do all functions of a bridge and do all the calculations internally, I decided I wanted it. The lead connection problem you have mentioned has always been a problem with devices that attempt to measure low values of resistance. The 4-wire Kelvin leads essentially eliminate that problem letting the device measure the lead LC and R, then calibrating those values out of its measurement circuit. All that is left then is to introduce measurement errors (other than operator errors) is contact resistance to the component under test. The Kelvin leads minimize that error by using gold (plated I suppose) heavy aligator clips to make the connection. In fact gold is used for the meter input slots and on both ends of the Kelvin leads. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 20, 2004 Share Posted March 20, 2004 Bob, The reason I'm using the GR bridge is that a fellow had one sitting around and wanted my filter software. I grand swap was done. The bottom line is that it cost me the price of harware key (dongle) which is $40! I have started looking for a newer HP LCR meter with a computer interface on it on eBay, but one hasn't come along yet. I want to be able to transfer a bunch of cap measuremnts to the computer and have it make matched sets from the list. Actually, one did, but I lost the biding! Al K. Quote Link to comment Share on other sites More sharing options...
BEC Posted March 20, 2004 Author Share Posted March 20, 2004 Al, You might want to read about and consider the B&K Precision 885. It does have a computer interface and I think using it that way even opens up some more capabilities. One of its uses is for production component sorting using a computer. Retail is around $565 plus $70 for the Kelvin test leads. I comes standard with a SMUD tweeser but that thing is unhandy for other uses. If you are interested, I can put you in touch with a source that will haggle on the price. I got for around $450 plus the Kelvin leads. Dealers are not supposed to discount B&K stuff, but some will. Bob Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted March 20, 2004 Share Posted March 20, 2004 Bob, I never considered B&K equipment before. The price for that model is about what a used HP would cost and it would not be calibrated! I have always been an HP and Tektronix fan and am sort-of stuck in my ways. I need time to get used to that idea! I'm in no hurry to upgrade though. The old GR is just slow going when you are matching a pile of caps, but it does do the job. AL K. Quote Link to comment Share on other sites More sharing options...
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