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Old ESR and LCR meters vs modern microchips ones ?
Posted by
lordvader88
on 20 Feb, 2018 20:38
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I don't have a proper ESR and/or meter but might have some extra money. What were 1970/80s ESR and LCR meters like vs today's ones. ?
If it breaks I sure would rather have meter's based on more discrete parts and also for now not SMD. But I'll end up with old and new soon of course.
Any thoughts? or recommendations of old ESR meters to look up to buy?
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#1 Reply
Posted by
tigr
on 20 Feb, 2018 22:10
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First, decide how much money you are willing to pay.
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Another thing to look at is what frequency of measurement are you looking at? 120Hz, 10kHz or 100kHz or above? Are you building power supplies and if so what kind of power supply? Mains transformer or SMPS?? Are you calibrating other equipment? RF?? Are you measuring ESR and how critical is that? What about "Q"? Not all meters will do that.
How accurate does it need to be? Over what time frame does it need to be stable?
This is the Metrology section, and those last two parameters would be more important to members here.
You sort of have to define the "need" first, and then match the equipment to that need.
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Hobby bench stuff with linear and SMPS's, RF, vacuum tube stuff too
They seem pretty expensive, and I don't see a bunch of old 2nd hand stuff on ebay. I guess for now either an Atlas ESR70 or a UT612 price range. They don't do everything, but its a good start.
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I've never seen the point of ESR meters. They only give you 1/3 of the story, and not usually at the frequency of interest. You need the value and you need the DC leakage, especially if you deal with tube stuff. Though expensive, the best ancient bridge for testing larger electrolytic caps is probably the GR-1617A. It can measure with up to 600 VDC bias and will give you leakage. For smaller caps, almost anything that gives you both value an dissipation factor in the range you need, will do the trick. If you're a switching power supply designer, ESR is of critical importance. If not, dissipation factor is the smarter number to work with.
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#5 Reply
Posted by
precaud
on 21 Feb, 2018 15:05
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For evaluating 'lytics over a wide range of voltages, I agree, the GR 1617 is excellent. But it's a specialized instrument.
As a reactance and low-impedance nut, I believe I've owned and used every LCR meter ever made from the the mid-1970's to mid-2000's or thereabouts. If you examine their spec sheets, you'll see that, for general-purpose use at mid- to low- frequencies, and in the middle of the impedance range, any one of them will probably be fine. It's at low impedances and high frequencies that their performance differs the most. Many of them do not have built-in fixtures for testing leaded components (the HP 426x and 427x series). And some of those that do are not useful for all types of components (the GenRad "Digibridges" won't measure radials with short leads).
Here's my short list of old favorites, stand-outs, and unique-and-worth-owning units (I own at least one of each), representing a range of impedance measuring techniques (which is a whole separate discussion):
General Radio 1608-A. The most accurate general-purpose manual bridge ever made. Amazingly stable. Easy to calibrate, if it ever needs it (mine hasn't). Replace 'lytics when they fail, and it will outlive you and you can pass it on to your son.
HP 4800A. Large front-panel meters directly read impedance and phase from 1 Ohm to 10 MegOhms, and from 5Hz to 600kHz. Accurate to below 1/10th Ohm by using rear panel plotter output. Low test signal level is good for in-circuit measurement. Easy to maintain and cal. Was my main ESR meter for many years, and still gets used. Good for reorienting your thinking away from "capacitance' and "inductance" and back to the raw impedance event. Formula for converting to L or C is on the front panel.
Wayne Kerr 4200 series, especially the 4210 and 4250. Builtin Kelvin fixture that works really well with all but SMD. Open/short compensation for nulling fixture residuals. Easy to calibrate. No exotic parts inside. The 4250 adds 100kHz freq and also has BNC outs for using your own fixtures/cables.
HP 4276A. Especially when used with a computer to automate the measurement, it is the most versatile audio-range impedance meter by far. Uniquely, it can directly measure the output impedance of active self-biased devices (i.e. batteries and DC power supplies) up to +-40V. Drawbacks: Requires external fixture/cables, and uses a couple custom Sony hybrid IC's that are unobtanium if they break. But this gets my nod as the most versatile impedance-measuring device.
For general-purpose use, all things considered, the WK 4250 is the stand-out. If you don't need 100kHz or external fixtures, the 4210 is just as good. For most versatile/capable, it's the HP 4276A.
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#6 Reply
Posted by
tigr
on 21 Feb, 2018 20:52
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I guess for now either an Atlas ESR70 or a UT612 price range. They don't do everything, but its a good start.
ESR70 is a very good device for in-circuit measurements. It would be great if it had a resolution of 0.001 Ohm. To measure LOW-impedance capacitors.
UT 612 has a resolution of 0.001 Ohm, but it is said that it has a two-wire measurement circuit. In addition, it does not support in-circuit measurements and does not have protection against charged capacitors, which ESR70 has.
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Many things I'm interested in have very low impedances. Out of all my old bridges and meters, about zero of them do well with that task. The old stuff is also limited in frequency. 10 or 20 kHz is typical, save for the old 716C, which can do a few hundred kHz or maybe 1 MHz with reduced accuracy. I doubt more than a dozen are still in service. Then things like the HP vector impedance meter can pick up again at 500 kHz, but again with nowhere near the accuracy of a bridge. There are things that can fill the hole, but not at used prices I can afford. Or, if you're rich, you can get modern LCR meters from Quadtech (Chroma) and Keysight, but they start at over $10k and twice that for a Keysight E4980A with all the options. We have a Keysight at the day job and it can measure just about anything up to 2 MHz with high accuracy. IMO, with modern DDS and other chips, those meters could be done by a sharp DIYer at a fraction of the cost. There's another interesting path I've yet to explore, though I use the free software frequently for other things. Visual Analyser (
http://www.sillanumsoft.org/) has an LCR feature I haven't tried. With the right interface it seems like it could very accurate.
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#8 Reply
Posted by
precaud
on 22 Feb, 2018 06:02
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Many things I'm interested in have very low impedances. Out of all my old bridges and meters, about zero of them do well with that task.
Conrad, I'm curious, what do you mean by "very low impedances" ? What range ?
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My favorite is the HP4192A. Very few modern meters can compete with it (and those that can do cost much more than the HP4192A in a good condition).
Cheers
Alex
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There's another interesting path I've yet to explore, though I use the free software frequently for other things. Visual Analyser (http://www.sillanumsoft.org/) has an LCR feature I haven't tried. With the right interface it seems like it could very accurate.
I also use VA for various things but for impedance and LCR I use Limp (part of Arta) it's is a more stable/mature/user-friendly program.
http://www.artalabs.hr/
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#11 Reply
Posted by
precaud
on 22 Feb, 2018 13:40
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My favorite is the HP4192A. Very few modern meters can compete with it (and those that can do cost much more than the HP4192A in a good condition).
The 4192A is a great piece of kit, but it's not great for low-impedance work... it actually disables the phase display when the impedance gets below 50 milliOhms!
My read of the OP's post is, he was not looking for the "absolute best" of the earlier generations of LCR meters (which tended to be quite large), but the best of the general-purpose, repairable-if-it-breaks ones.
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#12 Reply
Posted by
David Hess
on 22 Feb, 2018 20:40
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I have been getting by with an ESI 250DA impedance bridge which is easy to maintain but time consuming to use. I have been considering a DE-5000 which would allow me to make measurements at other than 1000 Hz but I think what I would prefer is an actual network analyser to get a better idea of what aluminum electrolytic capacitors are actually doing at higher frequencies.
None of these options are suitable for measuring a change in characteristics like leakage or capacitance with bias voltage. A dedicated capacitor tester might be nice but I have never seen one which does what I want.
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#13 Reply
Posted by
tigr
on 23 Feb, 2018 00:30
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Low Z for me would be zero to a couple ohms, 4-wire territory, up to maybe 100 kHz.
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#15 Reply
Posted by
precaud
on 23 Feb, 2018 01:49
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Low Z for me would be zero to a couple ohms, 4-wire territory, up to maybe 100 kHz.
With what kind of resolution over than freq range? MilliOhm? Lower?
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A few percent of reading would be plenty. I'll quote the manual for the somewhat odd GR 1603A Z-Y bridge, "...the ability to get an answer of any kind is often very valuable."
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#17 Reply
Posted by
precaud
on 23 Feb, 2018 14:56
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LOL. I remember lusting after a GR 1603A.. until I got one. Odd, indeed!
It is difficult to specify really low impedance measurements as % because "small" errors (from varying contact resistance of fixture and connectors, the impact of thermal changes on the instrument, DUT, fixture, etc.) become an increasingly large % of the measurement. Look at the specs for any LCR/Z meter and you'll see the accuracy specs loosen dramatically below say 100mOhm. Because of this, for low impedance measurements, I tend to look for repeatability first, and then accuracy as a "repeatably resolvable increment".
For the sake of discussion, let's say you want to measure down to a 1mOhm lower limit, with 100uOhm resolution, from (some low freq) up to 100kHz. (I choose 100uOhm resolution because my experience is, that is about the lowest repeatable resolution you can get with a high-quality bench DMM using 4-wire Ohms, and most won't even do that repeatably.)
I also sense that you want more freqs than just the spot decade ones (100, 1k, 10k, 100k).
So, of the multi-frequency oldies I've used that can be found for reasonable money :
HP 4276A meets the criteria, but only up to 20kHz.
Wayne Kerr 6425 comfortably betters it on all counts.
Ditto the ESI 2150/2160, but they're clumsy for bench use (user interface on the front, measurement terminals on the rear).
GenRad 1689x and 1693 models, but they are the darling of industry and still command higher $$.
With some math and programming, you can also do this with any decent DSA or VNA. Bring the measurement data into a computer and do the error correction and impedance conversion there.
You'll need either floating or isolated inputs, or isolated output (xfmrs work) so ground loops don't impact the measurement.
For 100kHz, the HP 3562A would be an excellent choice. You can float the inputs, and it has enough working registers and programming capability to be able to do the calculations on the fly and plot the results in "user units". (I use the 3562A's PC-based sister 3567A for this with excellent results.)
So, measuring low impedances up to 100kHz requires some care but is very doable.
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I'll have a look at those model numbers. On the 1603, it was the instrument that convinced me to write an impedance conversion program- a freebie you can download from my site.
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OK my wallet will have to wait for the older stuff too.
I ordered a Mastech MS5308
So that should do more than enough for now. And I get the Kelvin probes
I gather there was some external PSU issue a few years back, hope that doesn't bother me, it's very rare I would have all the batteries this thing needs, so I'll use a quality supply for sure.