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BMS001 and BMS002 Stepper Motor Controller
Motor
These parameters are used to set the 'resolution' characteristics of the stepper motor
connected to the selected channel. The resolution of the motor, combined with other
characteristics (such as lead screw pitch) of the associated actuator or stage,
determines the overall resolution.
Steps Per Rev - The number of full steps per revolution of the stepper motor
(minimum '1', maximum '1000').
Note. The Gearbox Ratio parameter is applicable only to motors fitted with a gearbox.
Gearbox Ratio - The ratio of the gearbox. For example, if the gearbox has a reduction
ratio of X:1 (i.e. every 1 turn at the output of the gearbox requires X turns of the motor
shaft) then the Gearbox Ratio value is set to X. (minimum '1', maximum '1000').
Notes.
•
The ‘Steps Per Rev’ and ‘Gearbox Ratio’ parameters, together with the ‘Pitch’ and
‘Units’ parameters are used to calculate the calibration factor for use when converting
real world units to microsteps (in the same way as the ‘Channel Calibration’ parameter
entered via the front panel when in ‘Local’ mode). However, the ‘Steps Per Rev’
parameter is entered as full steps, not microsteps. The system automatically applies a
factor of 128 microsteps per full step.
•
The stepper motors used on the majority of Thorlabs stages/actuators have 200 full steps
per rev and no gearbox fitted. For these motors the Steps Per Rev and Gearbox Ratio
parameters have values of 200 and 1 respectively. As an exception to this, the ZST family
of actuators use 24 steps per rev stepper motors fitted with a 76:1 reduction gearbox. In
this case, the Steps Per Rev and Gearbox Ratio should be set to '24' and '76' respectively.
The equivalent front panel calibration constant is then calculated as:
24 x 128 x 76 x 2 = 466944
24 steps per revolution
128 microsteps per full step
76:1 reduction gearbox
0.5mm lead screw pitch
•
The correct default values for Steps Per Rev and Gearbox Ratio are applied automatically
when the APTConfig.exe utility is used to associate a specific stage or actuator type with
a motor channel. See the APTConfig helpfile and the tutorial Section 4.2. for more
details.
