Magic Probe, any use it, and is it accurate?

[fscotte]

I built a similar device using the same tech, but each time I use my homebuilt I have to recalibrate it for the wood I am measuring.

I believe that the MagicProbe uses the same tech, which measures the magnetic force. That magnetic force is dependant not only on the distance between the magnets but also the density of the material. So spruce has more magnetic force than dense maple..

Just wondering if MagicProbe overcomes this issue? Seems like a worthy purchase if its accurate.

[mirwa]

A magnetic field cannot be affected by the density of a non magnetic material.

If you are referring too the material under inspection is compressible and affecting readings then that’s a different story, in this instance i would say the magnetic field strength you are using is too great and degaussing and remagnetising at a lower strength would be beneficial.

I have the magic probe and think it’s very neat and works well, inspection machines for measuring the thickness of non magnetic materials like this have been around a long long time.

Steve

[fscotte]

A magnetic field cannot be affected by the density of a non magnetic material.

If you are referring too the material under inspection is compressible and affecting readings then that’s a different story, in this instance i would say the magnetic field strength you are using is too great and degaussing and remagnetising at a lower strength would be beneficial.

I have the magic probe and think it’s very neat and works well, inspection machines for measuring the thickness of non magnetic materials like this have been around a long long time.

Steve

Thanks for that.

So it is accurate with very dense hard maple and then just as accurate with something like engelmann spruce? There are no adjustments needed?

If so, that is great. I'll have to look at my software again, maybe there is a sensitivity setting I can change on my homebuilt.

[sblock]

Thanks for that.

So it is accurate with very dense hard maple and then just as accurate with something like engelmann spruce? There are no adjustments needed?

If so, that is great. I'll have to look at my software again, maybe there is a sensitivity setting I can change on my homebuilt.

Yes, mirwa is absolutely correct. The magnetic permittivity of wood is all the same (and the same as a free space), so long as there's no ferromagnetic metal (iron, nickel, cobalt) situated inside the wood itself. The magnetic field strength is therefore entirely unaffected by wood. You should get the exact same reading for any wood of the same thickness, and no adjustments needed. If you don't, then either the wood is compressing an awful lot (rather unlikely) or your home-built system is not working properly and needs recalibration (more likely). As mirwa pointed out, you might be magnetizing the metal ball used to probe the field.

[Dale Ludewig]

I have a Magic Probe and it works great. FWIW, the ball (mine came with 2 different sizes) is magnetized. I think it's one of the rare earth magnets. I know this very well because not long after I got mine, I dropped the ball on the floor of my shop. It took about an hour of on my knees searching before I found it stuck to a caster underneath a cart.

[Steve Sorensen]

I found that the measurements tend to drift a bit over time. As with any good science, it pays to re-calibrate and take each measurement several times.

Steve

[Joe Mendel]

Another fan of the Magic-Probe here. Works great. It does pay a to take more than one measurement.

[David Houchens]

Really like mine.