So what exactly is needed to make this graph?

Possum · 09-25-2009, 03:58 AM

Yes but only at 120hz, and 1khz. It would be useful to have something that would measure at 20-20KHz

belwar · 09-25-2009, 04:27 AM

Correct me if im wrong, but the AC resistance shoudnt change depending on frequency should it? You should get the same reading regardless of frequency.. i.e. if you use an extech in SER mode, your readings at 120 and 1000 should be the same. See page three in the lane poor mm thread for an example set of measurements and you'll see the measurements are the same (or within the margin of error of the device).

belwar · 09-25-2009, 04:36 AM

... another thought, probably incorrect but a thought none the less! I dont know if this would work in AC as it would in DC.

You could hook up an oscillator to your pickup, as well as a good DMM. Select any frequency on the oscillator, and measure the Voltage and Current using a DMM.. Use the forumula R = V/I to calculate the resistance at that frequency. I'll try it tommorow.. I've set the oscillator @ 120 and then do the calculation. I'll compare that to the Extech reading.

David Schwab · 09-25-2009, 05:15 AM

Quote:

Originally Posted by belwar

Correct me if im wrong, but the AC resistance shoudnt change depending on frequency should it?

AC resistance increases with frequency. It's akin to impedance.

Possum · 09-25-2009, 05:40 AM

Yes AC resistance readings change with frequency, I use it all the time and its usually the first thing I look at,inductance is second, Q last.

Yeah I wonder.....use a driver coil with a frequency generator and measure output voltage from the pickup, might work, worth a try....

Possum · 09-25-2009, 05:58 AM

Hmmmmm, interesting. I hooked up my frequency generator to my driver coil set over a humbucker at right angles ala Lemme style. Plugged my DMM set on AC voltage and got a definite peak voltage at 8khz. Maybe I can try one of the cheapie free osciloscope programs to look for the signal to peak or just do it this way. At least I can see a peak at a certain frequency and use that as a baseline for comparative measurements. I used Joe's method before and never could find definite peaks in alot of pickups, maybe I was doing something wrong. ....

Possum · 09-25-2009, 06:35 AM

Tried Signalscope, interesting stuff but have no clue what I'm doing and can't discern peaks of any kind, looks like it won't do a frequency response chart....

belwar · 09-25-2009, 07:03 AM

** What im writing might not be factually accurate.. Im still learning at 100mph and I may be getting things wrong **

I just bought a USB scope (as seen in another thread) and i've already learned quite a bit from the device. It's purpose is to show Voltage (or current if set up correctly) over time.. Voltage on the vertical, time on the horizontal..

So bar I believe these Frequency response charts are done on Signal Analysers which might also be called Network Analysers. These devices show Voltage on the vertical, FREQUENCY (not time) on the horizontal. There is one built into the USB scope software I just got, but I havent got to mess with it yet.

I learned the very basics about scopes from a very cool set of you tube vids. I put them below. Dont worry they are short.

Part 1

YouTube - Oscilloscope Tutorial Part 1

Part 2

YouTube - Oscilloscope Tutorial Part 2

Part 3

YouTube - Oscilloscope Tutorial Part 3

belwar · 09-25-2009, 07:05 AM

Quote:

Originally Posted by Possum

Hmmmmm, interesting. I hooked up my frequency generator to my driver coil set over a humbucker at right angles ala Lemme style. Plugged my DMM set on AC voltage and got a definite peak voltage at 8khz. Maybe I can try one of the cheapie free osciloscope programs to look for the signal to peak or just do it this way. At least I can see a peak at a certain frequency and use that as a baseline for comparative measurements. I used Joe's method before and never could find definite peaks in alot of pickups, maybe I was doing something wrong. ....

Joes method hasnt let me down yet. Works like a charge. .. That was until I tried to measure a low impedance Lane poor.. I thought it was broken, just turns out the resonance peak was about the 20k my oscillator could go to...

Im thinking of building a oscillator as a learning electronics project.

Possum · 09-25-2009, 07:22 AM

Can you show me how your Joe test setup is done? In non-engineer terms with pictures done with crayons, third grade style :-)

Possum · 09-25-2009, 07:48 AM

I tried my method again with a strat bridge coil with iron loading, and get a defined peak at 9.2khz and rapid drop off from there. If oscilloscopes read voltage over time wouldn't what I'm doing be a valid method? Driving a coil with a low impedance driver coil and measuring the AC voltage coming out of the pickup? What could be simpler?

Joe Gwinn · 09-25-2009, 03:43 PM

Quote:

Originally Posted by David Schwab

Doesn't the Extech measure AC resistance?

Yes, exactly. Nor is the Extech even able to measure DC resistance.

09-25-2009, 03:58 AM	#36
Possum Old Timer Join Date: May 2006 Location: Planet Mongo in the country of PAF Posts: 3,140	... Yes but only at 120hz, and 1khz. It would be useful to have something that would measure at 20-20KHz __________________ http://www.SDpickups.com Stephens Design Pickups

09-25-2009, 05:40 AM	#40
Possum Old Timer Join Date: May 2006 Location: Planet Mongo in the country of PAF Posts: 3,140	Yes AC resistance readings change with frequency, I use it all the time and its usually the first thing I look at,inductance is second, Q last. Yeah I wonder.....use a driver coil with a frequency generator and measure output voltage from the pickup, might work, worth a try.... __________________ http://www.SDpickups.com Stephens Design Pickups

09-25-2009, 05:58 AM	#41
Possum Old Timer Join Date: May 2006 Location: Planet Mongo in the country of PAF Posts: 3,140	... Hmmmmm, interesting. I hooked up my frequency generator to my driver coil set over a humbucker at right angles ala Lemme style. Plugged my DMM set on AC voltage and got a definite peak voltage at 8khz. Maybe I can try one of the cheapie free osciloscope programs to look for the signal to peak or just do it this way. At least I can see a peak at a certain frequency and use that as a baseline for comparative measurements. I used Joe's method before and never could find definite peaks in alot of pickups, maybe I was doing something wrong. .... __________________ http://www.SDpickups.com Stephens Design Pickups

09-25-2009, 06:35 AM	#42
Possum Old Timer Join Date: May 2006 Location: Planet Mongo in the country of PAF Posts: 3,140	... Tried Signalscope, interesting stuff but have no clue what I'm doing and can't discern peaks of any kind, looks like it won't do a frequency response chart.... __________________ http://www.SDpickups.com Stephens Design Pickups

09-25-2009, 07:22 AM	#45
Possum Old Timer Join Date: May 2006 Location: Planet Mongo in the country of PAF Posts: 3,140	.... Can you show me how your Joe test setup is done? In non-engineer terms with pictures done with crayons, third grade style :-) __________________ http://www.SDpickups.com Stephens Design Pickups

09-25-2009, 04:27 AM	#37
belwar Supporting Member Join Date: Jul 2008 Posts: 770	Correct me if im wrong, but the AC resistance shoudnt change depending on frequency should it? You should get the same reading regardless of frequency.. i.e. if you use an extech in SER mode, your readings at 120 and 1000 should be the same. See page three in the lane poor mm thread for an example set of measurements and you'll see the measurements are the same (or within the margin of error of the device).

09-25-2009, 04:36 AM	#38
belwar Supporting Member Join Date: Jul 2008 Posts: 770	... another thought, probably incorrect but a thought none the less! I dont know if this would work in AC as it would in DC. You could hook up an oscillator to your pickup, as well as a good DMM. Select any frequency on the oscillator, and measure the Voltage and Current using a DMM.. Use the forumula R = V/I to calculate the resistance at that frequency. I'll try it tommorow.. I've set the oscillator @ 120 and then do the calculation. I'll compare that to the Extech reading.

09-25-2009, 07:48 AM	#46
Possum Old Timer Join Date: May 2006 Location: Planet Mongo in the country of PAF Posts: 3,140	... I tried my method again with a strat bridge coil with iron loading, and get a defined peak at 9.2khz and rapid drop off from there. If oscilloscopes read voltage over time wouldn't what I'm doing be a valid method? Driving a coil with a low impedance driver coil and measuring the AC voltage coming out of the pickup? What could be simpler? __________________ http://www.SDpickups.com Stephens Design Pickups

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