Induction sensor - installed in solid iron 1

[hpon]

Hi,

Do induction sensors work when surrounded by iron?

Let's say I have a large block of iron that has a long hole (8mm in diameter) going through it. An induction sensor is placed midway through the hole, and then a solid iron cylinder (8mm in diameter) is inserted from the opposit end of the hole and placed adjacent to the sensor. Will the sensor be able to measure the distance between itself and the cylinder, or will the surrounding material render that impossible?

/hpon

 

[Skogsgurra]

Not impossible. But your scale factor (assuming a linear output) or trip point (if on/off) will be affected. For the on/off version, you may have to test several brands and types before you find one that you can use.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Strong]

You need to specify the range of displacement detection you need. Induction sensors used for shaft proximity (displacement and vibration) only have about 80 mils (0.080 inches) range, and that's not in an iron hole! Consider using an LDVT if a contact rod can be used or look into fiber-optical probes.

Walt

 

[jraef]

Balluf makes inductive prox sensors that would work up to 12mm, and you can get them shielded so they can be embedded in ferrous metals. But the sensing zone is a cone that crosses at the apex and spreads out again, so depending on how deep it is in the hole you may end up sensing the walls of your block of iron anyway. However if you want an analog output to measure distance, the range on a sensor that will fit inside of a 8mm hole is only 2mm.

Infrared may be a better choice for this, ultrasonic if it's too dirty for optics.

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— Kilgore Trout (via Kurt Vonnegut)
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[hpon]

I appreciate your replies!

The sensor I'm currently considering has a fairly linear respons ranging from 0-5V, in the distance interval 0-4mm. Based on Skogsgurra's (jag kanske hör av mig dig senare. Lägger gke på minnet i alla fall) post I assume that the output range will be diminished due to the massive surrounding material, and perhaps rather nonlinear. This will reduce the accuracy of the distance measurment, but that might be OK.

Regarding the sensing interval. Should I expect any changes in particular? A longer, shorter or perhaps a translated (3-7mm for instance) range?

Jraef, I've thought about using light and sonic sensors, but the working environment is harsh (water, mudd, oil, -30C°, machanical impacts, mechanical wear) and I believe that rules out such sensors. Please let me know if that is not a valid conclution.

/hpon