# broken wrist metal plate..metal detector not finding **URL:** \ **Category:** Factual Questions\ **Created:** [January 8, 2013, 2:00pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477 "2013-01-08T14:00:07Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Sigene](https://avatars.discourse-cdn.com/v4/letter/s/df788c/32.png) [@Sigene](https://boards.straightdope.com/u/Sigene)\ **Post date:** [January 8, 2013, 2:00pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/1 "2013-01-08T14:00:07Z")
Last year I fell and broke my wrist. I wound up with a plate in it which is a very common occurance. I’m surprised when I pass my metal detector over my wrist, it has a difficult time registering it. This is a metal detector that I’ve used to find BB’s an inch or two underground. Are there any reasons why it would be so insensitive to a metal plate in my wrist? I don’t know if the plate is titanium, or stainless steel, but either way, I’d expect more signal. ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [January 8, 2013, 2:08pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/2 "2013-01-08T14:08:07Z")
What kind of metal detector are you using? Titanium and stainless steel implants are generally non-ferrous (not magnetic) and may not set off home metal detectors. You still may set off more sensitive airport style detectors. ---
**Author:** ![cuberdon](https://avatars.discourse-cdn.com/v4/letter/c/45deac/32.png) [@cuberdon](https://boards.straightdope.com/u/cuberdon)\ **Post date:** [January 8, 2013, 3:02pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/3 "2013-01-08T15:02:36Z")
> [@USCDiver](#): > > What kind of metal detector are you using? Titanium and stainless steel implants are generally non-ferrous (not magnetic) and may not set off home metal detectors. You still may set off more sensitive airport style detectors. Ferrous doesn’t mean magnetic, it means made of or containing iron. It is not entirely clear how stainless steel could be non-ferrous. ---
**Author:** ![USCDiver](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/uscdiver/32/354_2.png) [@USCDiver](https://boards.straightdope.com/u/USCDiver)\ **Post date:** [January 8, 2013, 3:14pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/4 "2013-01-08T15:14:02Z")
> [@cuberdon](#): > > Ferrous doesn’t mean magnetic, it means made of or containing iron. It is not entirely clear how stainless steel could be non-ferrous. :smack: you’re right. Regardless the point remains, titanium and stainless are generally non-magnetic ---
**Author:** ![EmAnJ](https://avatars.discourse-cdn.com/v4/letter/e/d2c977/32.png) [@EmAnJ](https://boards.straightdope.com/u/EmAnJ)\ **Post date:** [January 8, 2013, 3:18pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/5 "2013-01-08T15:18:12Z")
It’s probably a titanium plate. My husband has one in his arm as well and it’s not picked up by metal detectors. ---
**Author:** ![Nametag](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nametag/32/406_2.png) [@Nametag](https://boards.straightdope.com/u/Nametag)\ **Post date:** [January 8, 2013, 3:18pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/6 "2013-01-08T15:18:30Z")
It can still be non-ferritic, though. ---
**Author:** ![Bass\_Chick](https://avatars.discourse-cdn.com/v4/letter/b/43a26b/32.png) [@Bass\_Chick](https://boards.straightdope.com/u/Bass_Chick)\ **Post date:** [January 8, 2013, 3:28pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/7 "2013-01-08T15:28:57Z")
I have pins and a plate in my ankle. My husband’s metal detector will give a signal if it’s in close proximity. Boston Logan is the only airport that ever noticed it. ---
**Author:** ![Absolute](https://avatars.discourse-cdn.com/v4/letter/a/b2d939/32.png) [@Absolute](https://boards.straightdope.com/u/Absolute)\ **Post date:** [January 8, 2013, 3:56pm UTC](https://boards.straightdope.com/t/broken-wrist-metal-plate-metal-detector-not-finding/646477/8 "2013-01-08T15:56:15Z")
> [@cuberdon](#): > > Ferrous doesn’t mean magnetic, it means made of or containing iron. It is not entirely clear how stainless steel could be non-ferrous. He is probably confused because of the similar terms ferritic and ferromagnetic. Ferritic and martensitic stainless steels are ferromagnetic (i.e. magnetic) - austenitic (non-ferritic) stainless steels are not. These terms refer to different types of crystalline structure of the grains in the material. In any case - there are many different kinds, but in general, metal detectors work by emitting a oscillating magnetic field. This induces an oscillating electrical current in metal objects, and the resulting electrical oscillations in the object themselves produce a magnetic field. The induced secondary magnetic field can be sensed by the detector. Different metals have different degrees of magnetic permeability and electrical conductivity, which influence the degree to which they perturb the field of the metal detector. Fancy metal detectors can differentiate different types of metal by the timing and amplitude of the perturbation in the field, and adjust their sensitivity based on the type of metal being detected. Simple metal detectors generally just have a fixed sensitivity level, and will respond differently to different amounts of metals with varying permeability / conductivity. The shape of an object and orientation relative to the detector can affect detection as well. Airport metal detectors typically have their sensitivity set relatively low to avoid slowing down the lines by picking up zippers and other metal components in people’s clothing. Often these components are made of metal which responds relatively strongly to a metal detector, so it is not surprising that the detectors tuned to ignore such things fail to pick up larger, implanted objects made of material which responds less strongly. > **[Permeability (electromagnetism)](https://en.wikipedia.org/wiki/Permeability_(electromagnetism))** > > In electromagnetism, permeability is the measure of magnetization produced in a material in response to an applied magnetic field. Permeability is typically represented by the (italicized) Greek letter μ. It is the ratio of the magnetic induction > > > > B > > > {\\displaystyle B} > > to the magnetizing field > > > > H > > > {\\displaystyle H} > > in a material. The term was coined by William Thomson, 1st Baron Kelvin in 1872, and used alon In...