Strange electrical problem
 

I have been trying to adjust my mixture, this has happened twice now, I hook up my dwell meter to the test plug by the rear harness, while I make my adjustments, the battery is getting drained, and I mean quickly, the car stays running but in just a few minutes the tach begins to go hay wire and then dies completely, once I shut it off I have to hook up a battery charger, anyone have this problem? I verified my connections, positive on dwell meter to the green wire and negative to the brown wire, I need to use the meter method because I can't get my hands on an o2 meter, any ideas will be appreciated. :(

What kind of car, year etc? Need more info to troubleshoot. Something is not correct as you should not be able to run the battery down that fast.

I knew I was forgeting something duh!
 

Sorry, the car is a 911 80SC