Kaman KD-5100 - Manual (Page 10)

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5-2. Thickness
5-2a. The RF field developed by the sensor is at a maximum on the target surface. There is
penetration below the surface and the extent of penetration is a function of target resistivity and
permeability. The RF field will penetrate aluminum to a depth of 0.022”, a little more than three
“skin depths” (at one skin depth the field density is only 36% of surface density and at two skin
depths it is 13%). To avoid variations caused by temperature changes of the target, the minimum
thickness should be at least three skin depths.
5-2.b The depth of penetration depends on the actual target material used (Table 1). In cases
where the sensors are opposing each other, aluminum target thickness must be at least 0.050” to
prevent sensor interaction.
Table 1 Recommended minimum target thickness in mils.
Material Thickness in mils
Silver
and Copper 11-13
Gold and Aluminum 13-18
Beryllium 17
Magnesium, Brass, Bronze, Lead 26-39
300 Series Stainless 75
Inconel 95
5-3. Size
The minimum target cross section must be 1½ to 2 times sensor diameter.
6. SPECIAL HANDLING CAUTIONS
6-1. The Sensors
Due to design requirements, the sensor’s most critical component, the coil, is exposed. We ship
the sensors with protective caps. Keep them in place until installation of the sensors.
CAUTION: If any sharp object comes in contact with the coil face or edge and
damages it in any way, this could short a number of turns in the coil, alter its
impedance, and render it useless.