Anyone else measured inductors with WT3?

[XtremeRevolution]

This is thoroughly confusing. I'm getting the feeling that my WT3 might be defective. Every single inductor I test is too high of a value. I calibrated the WT3 using the provided resistor and the shorted leads calibration, and here's what I'm coming up with.

Jazten .30mH - measures .34mH
Jazten .25mH - measures .28mH
Erse 3.5mH solid core - measures 3.8mH

The other day, I was building my Florians crossovers which I had to unwind a 2.0mH inductor, and it measured 2.2mH. I unwound it to where it would measure 1.85mH thinking it was just a fluke. I then measured the .15mH inductor and it came up .17mH. I ended up unwinding it since I needed a .12 value.

Anyone having the same experiences? Am I missing something, or are these inductors all actually higher in value than they should be?

[johnnyrichards]

Re: Anyone else measured inductors with WT3?

I have the same results. It is what it is. I have no problems with caps and resistors, but I do with coils.

[XtremeRevolution]

Re: Anyone else measured inductors with WT3?

I have the same results. It is what it is. I have no problems with caps and resistors, but I do with coils.

Ok, so should I be unwinding them, or should I just leave them alone? Does that mean that ones I already unwound are now a lower value than they should be? If so, does it mean that I need to go pick up an LCR somewhere just so I can be able to unwind my own coils accurately?

[woodtradesman_audio]

Re: Anyone else measured inductors with WT3?

Time for an LCR maybe?

[Chris Roemer]

Re: Anyone else measured inductors with WT3?

This is thoroughly confusing. I'm getting the feeling that my WT3 might be defective. Every single inductor I test is too high of a value. I calibrated the WT3 using the provided resistor and the shorted leads calibration, and here's what I'm coming up with.

Jazten .30mH - measures .34mH
Jazten .25mH - measures .28mH
Erse 3.5mH solid core - measures 3.8mH

The other day, I was building my Florians crossovers which I had to unwind a 2.0mH inductor, and it measured 2.2mH. I unwound it to where it would measure 1.85mH thinking it was just a fluke. I then measured the .15mH inductor and it came up .17mH. I ended up unwinding it since I needed a .12 value.

Anyone having the same experiences? Am I missing something, or are these inductors all actually higher in value than they should be?

I'm SURE you're measuring Le at 1k (and not at 10k - which is in the "preferences"), 'cause otherwise I think your values wouldn't even be close.

In general, coils measure high for me, but where yours are running some +10% high, mine only measure a percent or 2 high.


Chris

[PWR RYD]

Re: Anyone else measured inductors with WT3?

I use mine to measure inductors all the time. I feel mine measures inductors VERY accurately and VERY repeatably. I have compared it to a high quality LRC meter (B&K) as well as a test rig I made up using a sine wave generator and calibrated resistor. All values agree within 0.5%. Like Chris mentioned, I set mine to measure at 10 kHz for small values (under 1 mH) and at 1 kHz for larger values.

FWIW - every Jantzen inductor I've purchased whether its a 20 gauge air core or a 15 gauge P-core has measured a few percent over spec. With the current cost of copper this really surprises me :eek:

[XtremeRevolution]

Re: Anyone else measured inductors with WT3?

I'm SURE you're measuring Le at 1k (and not at 10k - which is in the "preferences"), 'cause otherwise I think your values wouldn't even be close.

In general, coils measure high for me, but where yours are running some +10% high, mine only measure a percent or 2 high.


Chris

You really think that will skew my numbers by 10%? See below:

I use mine to measure inductors all the time. I feel mine measures inductors VERY accurately and VERY repeatably. I have compared it to a high quality LRC meter (B&K) as well as a test rig I made up using a sine wave generator and calibrated resistor. All values agree within 0.5%. Like Chris mentioned, I set mine to measure at 10 kHz for small values (under 1 mH) and at 1 kHz for larger values.

FWIW - every Jantzen inductor I've purchased whether its a 20 gauge air core or a 15 gauge P-core has measured a few percent over spec. With the current cost of copper this really surprises me :eek:

This is really strange. Like I said, mine just doesn't seem to be very measuring correctly right now. I might even call PartsExpress to have them replace it.

The thing is, if the default is 1khz for large values, my 3.5mH inductor still shouldn't be measuring 3.8mH.

[XtremeRevolution]

Re: Anyone else measured inductors with WT3?

Paging John Murphy?

The tech at PartsExpress I just chatted with told me I should talk to him about this.

[PWR RYD]

Re: Anyone else measured inductors with WT3?

I don't believe it automatically defaults to 1 kHz. If you change it to 10 kHz under the "Edit>Preferences" tab then it stays 10 kHz until you change it to 1 kHz and vise versa. You need to go to that tab and see what it is set for.

[Chris Roemer]

Re: Anyone else measured inductors with WT3?

I don't believe it automatically defaults to 1 kHz. If you change it to 10 kHz under the "Edit>Preferences" tab then it stays 10 kHz until you change it to 1 kHz and vise versa. You need to go to that tab and see what it is set for.

Yup.

Not really sure what 10kHz is for (tweeter T/S?).

I remember old CLIO data that would show Le at BOTH 1k and 10k. The values were NOT the same (I don't even think they were close? - but CRR).

With my (older) WT3, it doesn't measure uF directly, you have to measure resistance at a certain freq and do the math. NOW I always take my reading at 1000 Hz. uF and Le values near 1k are more relevant than at 10k anyway, 'cause that's a LOT closer to where your trying to roll something off (even most 3-way tweets cross closer to 1k than 10k).

Chris

[XtremeRevolution]

Re: Anyone else measured inductors with WT3?

Well, its too late to save the inductors on my Florians speakers as they've already been unwound. I've entered the predicted values (accounting for the 10% error), and the crossover actually looks slightly better than what I had originally planned on. The top end is about 1db quieter, which I don't mind much.

I will re-measure the inductors I measured earlier, specifying a 1k Le and report back tonight.

[billfitzmaurice]

Re: Anyone else measured inductors with WT3?

Mine never reads accurately, but it's no problem. I 'calibrate' it with the initial measurement, and assume that the coil is accurately spec'd from the manufacturer. Also, be careful not to coil the test leads or have them resting on any ferrous material, you'll read the inductance created in the leads by so doing.

[XtremeRevolution]

Re: Anyone else measured inductors with WT3?

Mine never reads accurately, but it's no problem. I 'calibrate' it with the initial measurement, and assume that the coil is accurately spec'd from the manufacturer.

I guess that's what I'll have to do. Thanks.

[daver]

Re: Anyone else measured inductors with WT3?

I use mine to measure inductors all the time. I feel mine measures inductors VERY accurately and VERY repeatably.

My WT3 also seems to measure accurately and repeatably.

From time to time, I sometimes take the impedance measurement file and run a curvefit through the data as a check. Typically, the air core coils that I use (18 or 20 ga for instance) are fairly consistent with the WT3 value, and fairly constant regardless of frequency. Often, they are slightly below the "nominal" value.

Maybe the 10% difference that you see consistently has something to do with your WT3 or computer settings?

Even so, all coils will have a tolerance. A lot of them that I use are stated to be +/- 3%. For all practical purposes, if you have a simulation program, see what happens if you vary the "nominal" value of the specified inductor by +/-3%, +/-5%, or even +/-10%. Is there an appreciable difference? Maybe or maybe not.

[XtremeRevolution]

Re: Anyone else measured inductors with WT3?

My WT3 also seems to measure accurately and repeatably.

From time to time, I sometimes take the impedance measurement file and run a curvefit through the data as a check. Typically, the air core coils that I use (18 or 20 ga for instance) are fairly consistent with the WT3 value, and fairly constant regardless of frequency. Often, they are slightly below the "nominal" value.

Maybe the 10% difference that you see consistently has something to do with your WT3 or computer settings?

Even so, all coils will have a tolerance. A lot of them that I use are stated to be +/- 3%. For all practical purposes, if you have a simulation program, see what happens if you vary the "nominal" value of the specified inductor by +/-3%, +/-5%, or even +/-10%. Is there an appreciable difference? Maybe or maybe not.

Earlier today I plugged in the vales of what my coils probably are after I unwound them too far in PCD, and the difference was minimal. I had a bit of a higher bump between 1000hz and 2000hz, and my tweeter's output dropped about 1-2db overall. Nothing too serious. My reverse null looks prettier and has a -43db dip. Still looks pretty good.