Micro or milli-Henry confusion?

[Bobman]

Having just read the excellent "Inside the metal detector" by George Overton and Carl Moreland, I notice that the book states all coils in mH which I assume is milli-Henrys. However, all other typical circuits refer to coils in terms of micro-Henrys. Now if the values of the book are multiplied by 1000 to get to micro- Henry's then the inductance for these coils appears massive. Where am I going wrong here please?
Regards
Bobman

[surfdetector]

Having just read the excellent "Inside the metal detector" by George Overton and Carl Moreland, I notice that the book states all coils in mH which I assume is milli-Henrys. However, all other typical circuits refer to coils in terms of micro-Henrys. Now if the values of the book are multiplied by 1000 to get to micro- Henry's then the inductance for these coils appears massive. Where am I going wrong here please?
Regards
Bobman

Generally you see coils for VLF machines as mH and for PI they are listed as uH.

[kt315]

Eric Foster detectors were with 1mH coil. so PI limited by this number on high.

[Carl-NC]

Where does the book state "all coils in mH?" Generally, coils are stated as to their actual value, whether in uH or mH.

[Bobman]

Hi Carl, the book certainly does not state all coils in mH! Just my very badly phased question unfortunately.Having had most to do with pulse coils which mostly appear to be 200 to 500 micro H as stated on page 146, I was surprised that other methods required substantially larger inductance for their coils. Being obviously a newcomer, I just needed someone to put me straight.

[Carl-NC]

OK, I now see what you mean. A common PI inductance is 300uH, but PI coils can be as low as 100uH and as high as 1mH or so. VLF TX coils are typically 100uH to 6mH and RX coils from 500uH to 30mH or more, with lower inductances used for higher frequencies such as in gold detectors (also in TR detectors). BFO coils are typically in the 50-200uH range.

[AK48]

sorry i move my post to another thread