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|3/3/2005 6:48 PM|
Is there an easy to use, and cheap Pickup Analyzer out there? I'm just starting out winding pickups and I would like to be able to measure the frequency response.
|3/3/2005 7:35 PM|
I know that mr. Helmut Lemme built such thing, and offers it (price on request) You can find information at: www.gitarrenelektronik.de and I can assure you that this man knows where's he is talking about...
|3/4/2005 7:43 AM|
On 3/4/2005 2:35 AM, maf-guitars said:
[QUOTE]I know that mr. Helmut Lemme built such thing, and offers it (price on request) You can find information at: www.gitarrenelektronik.de and I can assure you that this man knows where's he is talking about...
cheers, Marcel[/QUOTE]The pickup decription (in German) is at http://www.gitarrenelektronik.de/elektronik/messtechnik/messtechnik.html.
The Pickup Analyzer is described in English at http://www.buildyourguitar.com/resources/lemme/index.htm. This writeup seems to parallel the German description, if my schoolboy German serves.
The pricelist says to ask for a price. The specsheet says that 230 V power is required, but I imagine Lemme could be persuaded to make a 110 V version.
|3/4/2005 8:37 AM|
I know someone who asked for the price and it was something like $900. Frequency response can be measured using a minimal amount of test equipment along with a certain amount of knowlege.
Having made the measurements myself, I find that some of Lemme's diagrams are a bit misleading. I'm sure the guy knows what he's talking about, but he didn't use anything like 'real' data in his diagrams. He shows the Q of the frequency resopnse remaining constant as the resonant frequency droops, but in reality, the Q drops as resonant frequency drops. Also, the frequency response should drop off at low frequencies but he shows it as being perfectly flat.
One area where Lemme is in error is in his measurements of pickup capacitance. Capacitance cannot be measured directly; it must be calculated based on the pickup resonant frequency. His method relies on a direct measurement of pickup voltage but the presence of a voltmeter across the pickup throws off the pickup impedance and lowers the *measured* resonant frequency. This throws off the capacitance calculation and gives numbers that are too high. Fortunately, pickup capacitance has very little to do with the in-circuit response of a pickup, so the error doesn't do any harm.
|3/4/2005 7:50 PM|
I emailed Lemme last year and asked the price and some questions and got no reply, not very good customer support there. For $900 you make your own setup and have alot more goodies than that thing.....
|3/6/2005 1:29 PM|
On 3/4/2005 2:43 PM, Joe Gwinn said:
Measuring the inductance of guitar pickups is complicated. With a Maxwell bridge, the ohmic resistance and the winding capacitance both falsify the value significantly.
A better way: Measure the resonant frequency in combination with a known capacitance and estimate a rough value for the inductance. Then measure the self resonant frequency (without a capacitor parallel) of the coil and calculate the winding capacitance. Then measure the resonant frequency with a known capacitance again, adding the winding capacitance to its value. Then calculate the exact inductance.
Helmuth[/QUOTE]Maxwell bridges in particular were the standard way to measure low-Q inductances for something like a century, and were used by all the National Standards Labs, so his comment perplexed me. I questioned his comment about the Maxwell bridge, which does in fact handle ohmic resistance correctly (and self-capacitance has a negligable effect at 1,000 Hz), but never did get a reply.
As for measuring the self-capacitance, Mr Lemme is right on target, and there is no other way to do it. I have used an expanded version of his method, and it does work quite well. I got my expanded approach from a book published in the 1950s on the design of inductance coils. The approach follows:
Use a number of capacitors whose values are known to about 1%, find the resonant frequencies, and then solve for the unknown self-capacitance that best fits all those pairs of external capacitance and corresponding resonant frequency. If one works with L, C, and 1/(omega^2), where omega is the radian frequency at resonance, the fit is linear and all the constants become unity, much simplifying things. (The radian frequency is 2 Pi (~6.28) times the frequency in Hertz.) The fit can be done graphically as well; if all is well, the datapoints will fall on a straight line.
|3/4/2005 8:08 PM|
well not real sure on how much in the ball park the readings are but what i did is wound about 50 turns on a piece of balsa wood with the pickup shape i plug this into the audio out on my puter there a ton of generators and analyzer proggys out there then i feed the pick up to the audio in now for the absolute numbers this isn't 100% but it gives you a good visual of where the Q is ect ect and my sound card isn't the best but the higher end on the sb Audigy it works for me and for right now i don't have the $$$ to buy REAL equip to do the job so i make best of what i have ( or can find) on the net
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