Cycle Analyst V3.1 User Manual
Rev 1.0
High current shunt resistors for larger EV's do not typically
list their rating in mOhm. Instead they are characterized by
the current which will produce a full scale reading on a 50mV
(most common) or 100mV galvanometer. To calculate the
RShunt from one of these devices, divide the mV full scale
value of the shunt by the amps rating. For instance, a 200A
50mV unit has an RShunt value of:
50mV / 200A = 0.250 mOhm
It's worth noting that shunt resistors are large blocks of metal that can handle
significantly more current for short times than their "rated" current. Don't be
concerned if you have a 75A shunt but draw 150 or 200A peak currents, in
general this is fine.
Most high current shunts will be less than 0.8 mOhm and the Cycle Analyst must
be set to High Range (0.1A) mode to accomodate them. The High Range mode
will show power in kilowatts instead of watts, and current to the nearest 0.1A
instead of 0.01A.
6.13.1 Zero Amps
If the Cycle Analyst consistently shows a small positive or negative power even
when the motor is not running, it means that the amps offset needs to be zeroed
to recalibrate the no-current reference point.
This is done by pressing and holding the button on the “Zero Amps” setup
routine. The screen shows the actual output voltage from the two current
sensing amplifiers, and they should both be approximately 2.50V. If the resulting
voltages are widely different from this, it usually indicates a bad connection on
either of the shunt sensing wires (S+ and S-, white and blue respectively).
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