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Re: Its a damn close to official as possible

5/17/2006 8:58 AM
moocow	Re: Its a damn close to official as possible The Extech would freak out at 10kHz. The meter is designed to work with inductors that don't have a significant amount of winding capacitance. At 10kHz, the winding capacitance will throw off the reading. A better choice would be a digital LCR impedance bridge like this one: http://www.quadtech.com/products/products.asp?familyid=15 It measures the voltage vs. current characteristics of a component over a wide range of frequencies. Based on the data, the computer inside of the bridge calculates the values of inductance, capacitance, etc. that best fit the impedance data. The bridge can be programmed to expect a certain amount of winding capacitance so it won't be fooled as easily as the Extech at high frequencies. An even more accurate method is to take the digi-bridge data and use your own software to derive the component's characteristics. I'm not sure if the digi-bridge can model nonlinear characteristics such as eddy current losses, but that can be done using MATLAB. Unfortunately, the digital bridges are expensive, well over $10,000. Even some large companies don't have these in their labs. But at one time, I did have a chance to use one to study differences in guitar amplifier capacitors. I wasn't interested in pickups at the time so I never used it to study impedance characteristics. As for the magnet types, I wouldn't believe what anybody told me either. Even Seth Lover wouldn't know what kind of magnets were actually shipped to Gibson. I would only believe the results of a material science lab that gave me an analysis of the elements in the magnetic material. A quick way to do this would be to send an old Gibson magnet to a company like Arnold Magnetics and ask them to analyze the magnet and send you 1000 more just like it. I'm sure those guys have a good lab and they should do this sort of analysis if it means more business for them.

5/17/2006 8:58 AM

moocow

Re: Its a damn close to official as possible

The Extech would freak out at 10kHz. The meter is designed to work with inductors that don't have a significant amount of winding capacitance. At 10kHz, the winding capacitance will throw off the reading.

A better choice would be a digital LCR impedance bridge like this one:

http://www.quadtech.com/products/products.asp?familyid=15

It measures the voltage vs. current characteristics of a component over a wide range of frequencies. Based on the data, the computer inside of the bridge calculates the values of inductance, capacitance, etc. that best fit the impedance data. The bridge can be programmed to expect a certain amount of winding capacitance so it won't be fooled as easily as the Extech at high frequencies. An even more accurate method is to take the digi-bridge data and use your own software to derive the component's characteristics. I'm not sure if the digi-bridge can model nonlinear characteristics such as eddy current losses, but that can be done using MATLAB. Unfortunately, the digital bridges are expensive, well over $10,000. Even some large companies don't have these in their labs. But at one time, I did have a chance to use one to study differences in guitar amplifier capacitors. I wasn't interested in pickups at the time so I never used it to study impedance characteristics.

As for the magnet types, I wouldn't believe what anybody told me either. Even Seth Lover wouldn't know what kind of magnets were actually shipped to Gibson. I would only believe the results of a material science lab that gave me an analysis of the elements in the magnetic material. A quick way to do this would be to send an old Gibson magnet to a company like Arnold Magnetics and ask them to analyze the magnet and send you 1000 more just like it. I'm sure those guys have a good lab and they should do this sort of analysis if it means more business for them.

Replies:

Joe Gwinn On 5/17/2006 2:58 PM, moocow said:<... -- 5/18/2006 6:03 AM