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10-14-2009, 05:59 PM
| #1 |
| Supporting Member  Join Date: Jul 2008
Posts: 757
| Whats going on here.. Inductance / Zero Phase Resonance Question
Ok, I've been taking some measurements of a Bass Pickup this morning. The pickup is an 8 coil humbucker. The top row of 4 coils are in series together, as is the bottom, then the two sets are put together in series . Coming out of the pickup is 5 wires.. Wire1 : Start of Coil Set 1 Wire2 : End of Coil Set 1 Wire3 : Start of Coil Set 2 Wire4 : End of Coil Set 2 Wire5 : Common ground wire (grounding the poles, keeper, and magnets) I used the Extech LCR meter to measure inductance and Q and the two frequencies, using the serial setting. First off, considering the pickup has ceramic magnets, the pickup has a very high inductance! .. Second off, the inductance changed quite dramatically between the two frequencies, AND changed again when I added the common ground into the mix! Also, I measured the resonance frequency using both the Peak response and zero phase method and obtained dramatically different results, and different results again when I add in the common ground! So my questions are as follows: 1) Why the dramatic change in inductance between the two frequencies? 2) Why does adding the common ground change the results for both inductance, and resonance? 3) Which method of the resonance frequency measurement is providing me with the correct number? Here are the direct readings of the scope, DMM, and LCR meter.. (Signifigant digits not calculated) Inductance @ 120hz,Coils Only, No Common ground:18.008 Henries Inductance @ 1000hz, Coils Only, No Common ground: 15.303 Henries Inductance @ 120hz, Coils + Common Ground: 17.99 Henries Inductance @ 1000hz, Coils + Common Ground: 16.132 Henries Q @ 120hz, Coils Only, No Common ground: 0.6944 Q @ 1000hz, Coils Only, No Common ground:2.425 Q @ 120hz, Coils + Common Ground: 0.6891 Q @ 1000hz, Coils + Common Ground: 2.212 Zero Phase Resonance Freq without common ground: 3010 hz Zero Phase Resonance Freq with common ground: 2400 hz Peak Response Resonance Freq without common ground: 4552 hz Peak Response Resonance Freq with common ground: 2429 hz Bel, EDIT: All resonance measurements done with a 1 Megaohm Resistor between the signal generator and pickup. |
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10-14-2009, 06:22 PM
| #2 |
| Member Join Date: Jan 2008 Location: California
Posts: 43
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Because you didn't put in the crystals.  |
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10-14-2009, 06:38 PM
| #3 |
| Supporting Member Join Date: Jul 2008
Posts: 757
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I *so* need to see that movie. Dont you have non-boutique pickups to make?  |
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10-14-2009, 08:56 PM
| #4 | |
| Senior Member  Join Date: Jan 2008
Posts: 374
| Quote:
The CircuitGear 101 network analysis mode will give you the impedance plot and phase shift directly. *If there is a resonance peak, then you will see zero phase there too. Drive the pickup through a SERIES 1.5k resistor. Hook the A channel across the resistor+pickup. Hook the B channel across the pickup. Go to the network analyzer menu. Set the frequency range at 100Hz to 10kHz. Banzai! -drh | |
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10-14-2009, 09:04 PM
| #5 | |
| Pickup Maker  Join Date: May 2006 Location: Montclair, NJ
Posts: 5,583
| Quote:
__________________ Those who create are rare; those who cannot are numerous. Therefore, the latter are stronger. - Coco Chanel www.sgd-lutherie.com www.myspace.com/sgdlutherie www.myspace.com/davidschwab | |
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10-14-2009, 09:38 PM
| #6 | |
| Supporting Member Join Date: Jul 2008
Posts: 757
| Quote:
Anything you see of interest here? bel | |
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10-14-2009, 10:01 PM
| #7 | |
| Pickup Maker Join Date: May 2006 Location: Montclair, NJ
Posts: 5,583
| Quote:
Oh, the pickup... Was that the inductance for the row of coils in series? Or a single coil?
__________________ Those who create are rare; those who cannot are numerous. Therefore, the latter are stronger. - Coco Chanel www.sgd-lutherie.com www.myspace.com/sgdlutherie www.myspace.com/davidschwab | |
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10-14-2009, 11:23 PM
| #8 |
| Supporting Member Join Date: Jul 2008
Posts: 757
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... actually my avatar refers to time travel, so there you go! :> per salvarsanarium (or however they heck you type that)... Here are the Parrallel measurements Inductance @ 120hz,Coils Only, No Common ground:56.10 Henries Inductance @ 1000hz, Coils Only, No Common ground: 17.871 Henries Inductance @ 120hz, Coils + Common Ground: 56.34 Henries Inductance @ 1000hz, Coils + Common Ground: 19.40 Henries Q @ 120hz, Coils Only, No Common ground: 0.6830 Q @ 1000hz, Coils Only, No Common ground:2.341 Q @ 120hz, Coils + Common Ground: 0.6891 Q @ 1000hz, Coils + Common Ground: 2.212 per David Schwab Row 1: Serial Setting Inductance @ 120hz, 4 Coils Only, No Common ground:9.634 Henries Inductance @ 1000hz, 4 Coils Only, No Common ground: 7.916Henries Inductance @ 120hz, 4 Coils + Common Ground: 9.638Henries Inductance @ 1000hz, 4 Coils + Common Ground: 8.054 Henries Q @ 120hz, Coils Only, No Common ground: 0.7347 Q @ 1000hz, Coils Only, No Common ground:2.396 Q @ 120hz, Coils + Common Ground: 0.7333 Q @ 1000hz, Coils + Common Ground: 2.314 Parallel Setting Inductance @ 120hz, 4 Coils Only, No Common ground:27.54Henries Inductance @ 1000hz, 4 Coils Only, No Common ground: 9.298Henries Inductance @ 120hz, 4 Coils + Common Ground: 27.57 Henries Inductance @ 1000hz, 4 Coils + Common Ground: 9.560 Henries Q @ 120hz, Coils Only, No Common ground: 0.7347 Q @ 1000hz, Coils Only, No Common ground:2.395 Q @ 120hz, Coils + Common Ground: 0.7333 Q @ 1000hz, Coils + Common Ground: 2.313 Row 2: Serial Setting Inductance @ 120hz, 4 Coils Only, No Common ground: 9.640 Henries Inductance @ 1000hz, 4 Coils Only, No Common ground: 7.916Henries Inductance @ 120hz, 4 Coils + Common Ground: 9.635 Henries Inductance @ 1000hz, 4 Coils + Common Ground: 8.044 Henries Q @ 120hz, Coils Only, No Common ground: 0.7274 Q @ 1000hz, Coils Only, No Common ground:2.387 Q @ 120hz, Coils + Common Ground: 0.7274 Q @ 1000hz, Coils + Common Ground: 2.312 Parallel Setting Inductance @ 120hz, 4 Coils Only, No Common ground:27.83Henries Inductance @ 1000hz, 4 Coils Only, No Common ground: 9.308Henries Inductance @ 120hz, 4 Coils + Common Ground: 27.91 Henries Inductance @ 1000hz, 4 Coils + Common Ground: 9.550 Henries Q @ 120hz, Coils Only, No Common ground: .7259 Q @ 1000hz, Coils Only, No Common ground: 2.387 Q @ 120hz, Coils + Common Ground: 0.7252 Q @ 1000hz, Coils + Common Ground: 2.310 Do you want me to un solder one coil and measure that david? matt |
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10-15-2009, 02:01 AM
| #9 |
| Old Timer  Join Date: May 2006 Location: Planet Mongo in the country of PAF
Posts: 3,103
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Well you left out some important information like DC resistance of each coil and AC resistance readings. Usually when there's a big difference between 120hz and 1khz readings it means there's alot of metal in there and/or the use of fine wire.....
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| The Following User Says Thank You to Possum For This Useful Post: | soundmasterg (10-16-2009) |
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10-15-2009, 02:05 AM
| #10 |
| Pickup Maker Join Date: May 2006 Location: Montclair, NJ
Posts: 5,583
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A lot of metal for sure! Four small coils in a "coil set". About 2.4K each, if I remember right.
__________________ Those who create are rare; those who cannot are numerous. Therefore, the latter are stronger. - Coco Chanel www.sgd-lutherie.com www.myspace.com/sgdlutherie www.myspace.com/davidschwab |
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10-15-2009, 03:22 AM
| #11 | |
| Old Timer Join Date: May 2006 Location: Boston, MA area
Posts: 1,293
| Quote:
Unsoldering one coil so we can seen the four inductances would be useful: A alone, B alone, A+B, A- B. | |
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