Instruction manual
Q & A with Laurence
80Understanding your X-TERRA - Technology
Q
A
If most metallic targets have both ferrous and non-ferrous
properties, what triggers whether a specic target registers in
the ferrous range (negative TID numbers) or the non-ferrous
range (positive TID numbers) on the X-TERRA?
There are three “ingredients” of a target that determin its TID.
These are:
1) Conductance
2) Inductance
3) Magnetic response
Ferrous Objects
Ferrous objects are very interesting, because they have all three properties:
• they have conductance – current ows through iron but not very well,
• they have inductance – due to their shape, the currents ow along
certain paths and cannot vary easily,
• they also have a magnetic response, because iron is a magnetic material
and enhances the magnetic eld.
Tx
Rx
Time delay
Transmit (Tx) and Receive (Rx) wave forms
Non-Ferrous Objects
Non-ferrous objects, for example gold rings or coins, lack the third ingredient
and thus they only have two properties:
• they have conductance – current ows through
them better if they are thick and if they have good
conductivity, like copper, aluminium, gold,
• they have inductance – rings and coins in particular
have well dened paths for the current due to their
symmetry.
Rx
Tx