? on Mr Hall Effect

[Bruce Plecan]

In the past, I done some trouble shooting with Hall Effect Devises.
Now, for the first time I hooked a meter to one with it sitting on the
table.  The one I'm starring at is a Toyota, it has a red lead, a white
lead, and a sheilded cable with ground.
  So being the Cone Shaped Hat Wearer that I am, I did the following.  Using
a 9v battery, I grounded it to the shell of the sensor
applied + to the read lead, grounded the meter (DVM on V),
hooked the meter's lead to the white wire, and then tested it.
The test being held a gm crank disc near the tip of the toyota
sensor.  The meter just flickers as I expose it to the metal?.
I thought it would open and close as the metal came close to it?,
yes/no?..
  In various gm training references they show a pattern like

       ___       ___       ___       ___
___I      I___I     I___I      I___I      I

Can someone splain this to me, or refer me to an online source for
accurate info?.
Thanks
Bruce