Encoders - Prior Scientific ProScan III Manual

4.15 Encoders

Prior stages can be equipped with either linear or rotary encoders for higher
positioning repeatability and accuracy.
A linear encoder is an optical system that reflects light off a graduated scale through a
grating and onto photo sensors.
electrical currents generated are used to determine distance and direction the stage has
travelled. Unlike rotary encoders which imply a distance travelled by measuring the
rotation of the motor, linear encoders/scales are actually mounted to the moving plates
of a stage and therefore directly measure stage movement.
Linear Encoders benefit the stage user by providing:
• The ability to use a Digital Read Out (DRO)
• The ability to provide closed loop "servo" control
• Superior precision and finer resolution.
Linear scales mounted on Prior stages now provide repeatability to +/- 0.3 microns and
resolution (step size) as small as 50 nanometres (for the linear stages). This superior
performance is extremely critical in many industrial and bioscience applications such as
the performance of time-lapse photography studies.
An encoded controller will have 3 or 4 round 12 pin connectors on the back of the
control box labelled, "X Axis", "Y Axis", etc. Turn the controller off and plug in the
appropriate encoder or scale that corresponds with the appropriate axis.
The linear scales also have a home or reference position. This is a specific mark on the
scale that is read by the controller and it can be used to establish the same reference
position at any time. To use this feature, see the commands SIS and RIS described below.
When an encoder is fitted and enabled (the default condition) the controller uses the
position measured by the encoder as the true position and not the number of pulses sent
to the stepper motor.
The controller will sense which encoder input has an encoder fitted. It will control the
individual axis using motor pulses or encoder pulses depending on whether that axis has
an encoder fitted (and enabled).
© Prior Scientific Instruments Ltd
These sensors generate electrical currents.
Version 1.12 June 2017
ProScan® III Manual
The
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