How to check if pickups are in phase with a digital m.meter

[wgen]

Dear all,
I have a cheap Telecaster knockoff that I bought used, which I really like. It has a ceramic neck pickup, with also a brass cover. I needed to replace it, the sound with this one is dull and really, really dark. I bought a Tonerider Vintage Plus neck pickup, which has been analyzed by Antigua in this forum.
I was wondering how to check if this pickup will be in phase with the stock bridge pickup of this guitar, when toggle is in central position.
I found this video on Youtube:



Could you please tell if this method might be fine? I really couldn't tell if this is reliable or not. Thank you so much.

[antigua]

That's pretty clever. It would have been nice if he explained why it works the way it does, but I suppose most people wouldn't care anyway. 

I always used whole sets, so I've never had a need, but lately I'm setting up HSS and HSH Strats, and I'm having to cobble sets together for the first time, so this will come in handy.

[JohnH]

It can be done, try tbis too, using voltage rather than resistance:

guitarnuts2.proboards.com/thread/4938/testing-phase-screwdriver-pull-test

.....But tbat video uses a different method and didn't give any proof or explanation at all. Confusing and I don't believe it yet

It could be that the dc pulse caused by lowering the metal object throws off the current flowing to measure resistance, either boosting or suppressing it.

He should have demonstrated by reversing leads and then retesting

[antigua]

Mar 28, 2020 15:20:40 GMT -5 JohnH said:

It can be done, try tbis too, using voltage rather than resistance:

guitarnuts2.proboards.com/thread/4938/testing-phase-screwdriver-pull-test

.....But tbat video uses a different method and didn't give any proof or explanation at all. Confusing and I don't believe it yet

It could be that the dc pulse caused by lowering the metal object throws off the current flowing to measure resistance, either boosting or suppressing it.

He should have demonstrated by reversing leads and then retesting

Yeah it works by confusing the multi-meter's DC reading with a positive or negative transient pulse. It's a novel usage of a DC meter to observe an AC signal.

[JohnH]

I tested it, and it can work, I think there is a good idea here. But the vid leaves out some key points:

The way it works is similar to how the Screwdriver pull-off test works in my post above, but its a different way of detecting it that might work better with some meters.

When you run a resistance test, a small dc current passes through the pickup, in a direction determined by which meter lead goes to which pickup lead. It is important to keep this consistent, eg, always use the black meter lead to go to whichever pickup lead you want to check for being the ground connection.

When a ferrous object is moved in the vicinity of the pickup, it induces an added voltage in the pickup, just as a moving string does. If the moving object moves only in one direction, then this signal is a one-direction dc pulse. In the method I posted about before, this was then detected by various ways of detecting a dc signal, including an analogue or digital dc voltmeter. When a resistance range is used instead, the pulse is messing with the current flow by which the meter is deriving resistance and confusing it, and so it reads higher or lower.

To get a smooth consistent one-direction pulse, it is better to lay the ferrous object onto the pickup, let everything settle, then pull it up and away quickly and smoothly. If you try to watch the reading as you first place it on, then there is uncertainty as the object first accelerates/gets closer to the pickup, then has to slow down and stop, causing both a plus and a minus signal.

I tried in on a neck Strat pickup, in my guitar (can be fully wired, doesn't need to be just a separate pickup, just max the volume). Depending which way round I had my meter leads, I could get the basic 6.0k reading to briefly rise to 6.2k or fall to 5.8k. And switching to the RWRP middle pickup, its all the same because it is wired to be in phase.

[wgen]

Thank you for all the insights, and also for the other methods, I will try with the pc and sound card soon.

Mar 28, 2020 18:20:56 GMT -5 JohnH said:

I t

To get a smooth consistent one-direction pulse, it is better to lay the ferrous object onto the pickup, let everything settle, then pull it up and away quickly and smoothly. If you try to watch the reading as you first place it on, then there is uncertainty as the object first accelerates/gets closer to the pickup, then has to slow down and stop, causing both a plus and a minus signal.

I tried in on a neck Strat pickup, in my guitar (can be fully wired, doesn't need to be just a separate pickup, just max the volume). Depending which way round I had my meter leads, I could get the basic 6.0k reading to briefly rise to 6.2k or fall to 5.8k. And switching to the RWRP middle pickup, its all the same because it is wired to be in phase.

Yeah, I found this exact behavior, too. The reading caused a plus reading, then a minus reading soon after with my digital multimeter, so I was a bit confused.

One question about something related :
Let's say my new Telecaster neck pickup with cover is out of phase with the stock bridge pickup. I then would switch the white and black leads connections of the neck pickup to make it in phase. Do I also have to unsolder the grounding of the cover, underneath the pickup, and switch the soldering of this to the white instead of the black, which is how it comes stock?
What happens if I leave the grounding of the cover as it is stock?

[JohnH]

If you leave the cover connected as it is and swap the wires, the cover is now hot and may pickup some noise. So better to ground the cover to the new ground.

But if possible, it's just as good to swap wires on the other pickup instead. No change in tone either way once they are in phase.

[ms]

The ohm meter measures the ratio of voltage to current.  The approaching steel object gets increasingly magnetized as it approaches, inducing a flux change through the coil with a sign depending on the magnet polarity.  Of course, even if the magnetization remained remained constant, it would still cause a flux change because the field is stronger nearer the approaching object. A voltage is induced in the coil, which alters the V/I ratio.  The steel object abruptly stops and the flux change stops also and the voltage in the coil goes to zero.

[antigua]

I'm sure this works a lot better with an analogue multi-meter. With the digital type you have to hope that it will update fast enough to be observed. For whatever reason, the DE-5000's DCR mode is super slow, so I dont think it would work well with that model, but once the DE-5000 finally returns a value, it returns three to four points of  precision. 

[newey]

JohnH's sound-card method works best, I think, if one doesn't have an analogue meter.

[timtam]

To my mind, an analog ammeter is probably the definitive method. But the screwdriver test seems to work with current, voltage, or resistance. It's more a matter of how easy it is to see the deflection direction. I have a +/- 50uA centre-zero ammeter in a box like that suggested by Wacker (no power required):
www.premierguitar.com/articles/25683-mod-garage-build-a-pickup-phase-tester-part-1

If I was buying another one I would get one of these, which probably doesn't need the box ...
www.ebay.com/itm/1x-Analog-Panel-Meter-50-0-50uA-Military-USSR-Current-DC-Ammeter-M4247/192800826295