I got this description from sonoboy:
<p>
Hi Dr Mike,<br>
   I believe I have the proper e-mail address. Here are the images taken <br>
with a PC oscilloscope. The <a href="./Alnico.jpg">alnico image</a> is suspect because it was a cast <br>
magnet and also had messes up poles. When they shipped the magnets they were <br>
all stuck together because they were in plastic bags. Anyway, The current <br>
pic from channel 2 shows the coil current only as the voltage across a .1 <br>
ohm resistor. 3 volts or 30 amps. When I activated channel one all digital <br>
readings defaulted to channel one so you will see the DV reading change with <br>
scale. The input <a href="./Current.jpg">current</a> remained the same throughout. I did not notice any <br>
timing differences with magnet distance and so I simple set for scale / 
distance that gave a good response.<br> <a href="./Sneo.jpg">sneo</a> is sintered neodymium, 
<a href="./Bneo.jpg">bneo</a> is 
bonded neodymium, <a href="./Scobalt.jpg">scobalt</a> is sintered samarium cobalt, <br>
<a href="./Alnico.jpg">alnico</a> is cast, 
<a href="./Rubber.jpg">rubber</a> is a stacked cheap rubber strip type (probably ceramic) 
<a href="./Ceramic.jpg">ceramic</a> is 
sintered ceramic. <br>There is some ringing in the signal as well as noise. I 
need to add a buffer circuit as the signal decays<br> too rapidly to show slow 
respose times especially if they are buried in the signal.<br>
Regards<br>
sonoboy<br>