Product category:
Rotary Position, Tilt and Angular Sensors
News Release from: Newall Electronics | Subject: ScrewCoder
Edited by the Engineeringtalk Editorial
Team on 16 October 2002
Screw marries encoder for true linear
positioning
The ScrewCoder is an industry first that combines a lead screw assembly with a linear encoder.
The ScrewCoder is an industry first that combines a lead screw assembly with a linear encoder True straight-line positioning is now possible as the nut and screw are integral parts of the measuring components
This article was originally published on Engineeringtalk on 16 Oct 2002 at 8.00am (UK)
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As opposed to the traditional separate lead screw and rotary encoder assembly, the accuracy of the ScrewCoder is not influenced by screw pitch or reversal errors.
This is due to the fact that the nut is the actual reader head and the lead screw is the actual scale.
This provides for true straight-line linear measurement of the axis that is generated from a rotary movement.
In addition, the system does not require period recalibration due to screw wear and it will not misread due to geometric errors such as pitch, roll and yaw of the machine.
The ScrewCoder is based on Newall's Spherosyn technology which operates on the principle of induction.
A drive coil contained within the nut generates an electromagnetic field.
This field interacts with high precision steel balls that are contained in the screw.
A set of pickup coils detect the variations of the induced field, which are then combined and processed to generate signals that vary in sine and cosine form caused by axial (not rotary) movement along the scale.
The degree of phase shift between 0 and 360 degrees is related to the position of the nut over a ball.
A high-speed digital signal processor samples the signals and converts them from their natural analogue state to an industry standard differential quadrature at TTL levels.
The DSP also synchronises the periodic reference marker pulse to the A and B high output levels.
The ScrewCoder offers accuracy to +/-10um, includes the performance benefits of an IP67 rating, and is highly shock and vibration resistant.
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