Magnetic Field Meter

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "J. B. Weazle McCreath by way of Terry Fritz <twftesla-at-uswest-dot-net>" <weazle-at-hurontel.on.ca>


Hello Coilers,

I built a handy little test instrument last night that some of you who
are into the measurement of Tesla coil parameters might find handy.
Rather than picking up the electric field, as an R.F. signal strength
meter does, this unit responds to the magnetic field generated by the 
Tesla coil.

The five components, a 50 uA. meter, a 1N914 diode, a 0.005 disk cap,
a 1000 ohm resistor, and a solenoid coil with a ferrite rod core, are
all assembled in an aluminum box measuring 1.5" x 2" x 4".

The solendoid with its ferrite rod core is mounted side to side in the
box with the rod ends protruding thru the box sides and supported by
grommets.  A saw cut across the back of the box and ending at the two
holes for the grommets prevents the case from appearing as a shorted
turn to the solenoid.

The wiring is straight-forward with one end of the solenoid being tied
to ground, the other end connected to the anode of the 1N914 diode.
The cathode of the diode goes to the + terminal of the meter, while
the - meter terminal connects to one end of the 1000 ohm resistor,
the other end being grounded.  The capacitor is connected directly
across the meter terminals.

The unit appears to be quite sensitive, picking up the magnetic field
of a small fan motor from over a foot away.  I'm waiting for my shop
to warm up before I try it out on the Tesla coil to see what pattern
and strength it produces.


73, Weazle, VE3EAR/VE3WZL

Listening: 147.030+ and 442.075+
E-mail:    weazle-at-hurontel.on.ca
           or ve3ear-at-rac.ca
Web site:  www.hurontel.on.ca/~weazle