The way the controller works is to start with the feild current at max and the motors speed control is all carried out on the armature current and supply.
Above something like 20mph or there abouts theres nothing left on the armature and its running at full chat so the only way now to get more speed out of the motor is to start weakening the feild current to it , so the controller now holds the amature at full whack and the throttle pedal now starts to control the feild winding current and backs it off to allow the motor to increase speed and hence more throttle makes the controller supply less currently to the feild and hence increases the motor speed.
Does that make sence.
So if you hold a steady throttle position you will feel the controller go through the transitional period where its going from controlling the motors armature current to the feild current , pretty clever stuff really
The Eco meter does sort of show current out but its not that acurate as such but generally you can say anything in the green upto the yellow area is less than 100A or there abouts .
Try this link and use the next button, it tells you all about motors
http://www.tpub.com/content/doe/h1011v2 ... v2_112.htm
Our motor in the blingo in Fig7 is (a) i.e seperately excited.
ChrisB