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Old 13th February 2014, 11:15 PM   #1
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Default Finding a low cost high accuracy method for measuring inductance/capacitance

So, to back up my theory that effective stereo imaging requires well matched crossover components in the stereo pair, I'd like to be able to measure inductance and capacitance values with some degree of accuracy (at least 1%) unfortunately finding a low cost way to do this is proving very tricky. Can anyone recommend a suitable solution? I dont mind ebay bargains!

Presuming that a low cost solution does not exist, I was considering building a suitable jig to allow impedance measurements in arta, using a high quality referrence resistor and arta's built in calibration facility, do people think this would work and is it the best budget option?

I should probably mention that I'd be using the built in sound card
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Old 13th February 2014, 11:20 PM   #2
Einric is online now Einric  United States
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I have one of the LC100-A find that it works just fine for everything I need.
It is accurate on the Capacitance & Inductance on par with my Fluke 289.
Be aware that there are a couple of versions of this unit and I have the LC100-A.
Search on E-Bay and you will find it, a place called chip_partner has them on sale for $25 which is super cheap.
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Old 13th February 2014, 11:33 PM   #3
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Since you are interested in matching (rather than absolute value), perhaps a Wheatstone Bridge with AC excitation would give you perzackly what you want.
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Old 13th February 2014, 11:46 PM   #4
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Quote:
Originally Posted by Mark Johnson View Post
Since you are interested in matching (rather than absolute value), perhaps a Wheatstone Bridge with AC excitation would give you perzackly what you want.
I like that thinking, I'd thought of it before but forgotten... in theory that shiuld give me more accurate matches for components. The plan only slips up when I want to measure old caps to ensure they're still performing to specification.

I presume you were thinking of the obvious implementation of this... hang on, is it obvious? Just realise my initially planned implementation was to take a positive line out, connect that to two capacitors and send each side back in through the L/R channels individually, all would share ground... would a bridge really improve accuracy or just linearity?
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Old 13th February 2014, 11:50 PM   #5
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Quote:
Originally Posted by Einric View Post
I have one of the LC100-A find that it works just fine for everything I need.
It is accurate on the Capacitance & Inductance on par with my Fluke 289.
Be aware that there are a couple of versions of this unit and I have the LC100-A.
Search on E-Bay and you will find it, a place called chip_partner has them on sale for $25 which is super cheap.
That looks pretty awesome, how accurate is it?
I found one on ebay for a great price but the description says it only goes up to 10uF, is that right? Would be good to measure higher, but I guess I could measure with a low value cap in swries and calculate actual value from there...
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Old 14th February 2014, 12:11 AM   #6
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Quote:
I presume you were thinking of the obvious implementation of this... hang on, is it obvious? Just realise my initially planned implementation was to take a positive line out, connect that to two capacitors and send each side back in through the L/R channels individually, all would share ground... would a bridge really improve accuracy or just linearity?
It would be a dedicated piece of test equipment which connected to a pair of standalone, barenaked, not-in-circuit, AC impedances in their pristine virginal state, immediately after unpacking from the manufacturer's shipping carton. The equipment would tell you how many percentages the two impedances differ by (at the frequency of the AC excitation signal).
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Old 14th February 2014, 12:15 AM   #7
Einric is online now Einric  United States
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10uF in the standard mode, if you push the HiC button it will go to 100,000uF.
My Fluke 289 is a $600 multimeter and the LC100-A readings were well within any expected tolerance.
When matching components you want repeatability, once you know that a 1uF capacitor is within +- .01uF every time then you can match components relative to each other.
If you need a 1.0000uF capacitor then get ready to pony up big bucks for bench grade equipment.
But if .99uF to 1.01uF is close enough then the $25 outlay is more than reasonable for measurements on par with a $600 Fluke multimeter.

Last edited by Einric; 14th February 2014 at 12:17 AM.
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Old 14th February 2014, 12:51 AM   #8
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Well, recommendations can't get better than that, I'll order my new toy
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Old 14th February 2014, 06:40 AM   #9
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You could check out Peak Electronic Design in the UK

They do two varieties of LCR meter.
Not cheap, but not expensive either.

LCR45 @ 100
Atlas LCR @ 90
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Old 14th February 2014, 08:28 PM   #10
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I had a Peak/Atlas LCR meter & it blew out in less than 6 months. Also the leads broke off...
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