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.
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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