Rotary Measurement Technology
BOGEN products support customers with diverse solutions for rotary measurement, both incremental and absolute. Rotary solutions are used for continuous or discrete positioning, motion control, such as commutation, and many other solutions.
Rotary measurements requires two components:
- Rotary sensing heads
- Rotary scales
BOGEN develops and produces both absolute and incremental angle measurement solutions. In the combination of individual sensing head and task-specific scale, an optimal rotary measuring solutions can be developed.
Dipole rotary shaft end encoder
The most simple rotary measurement solution is a shaft end encoder, where an array of hall cells is measuring the orientation of a dipole magnet. The measurement of the position of the dipole magnet is absolute, since the orientation can be determined in relation to the hall cell array.
Hollow shaft, off axis encoder
Sensing heads that measure not at the shaft end and in the middle of the shaft are called off axis encoder. The off axis encoder can be used with hollow shafts to provide many different uses. The magnetical scale can be on the flange, on the outer or the inner diameter allowing for a high level of design freedom.
Rotary sensing heads
BOGEN offers a wide product range of linear sensing heads.
BOGEN Off Axis Sensing heads for counting
BOGEN Off Axis Absolute Sensing heads for position measurement and motion control
BOGEN can adapt these sensing heads for different applictaions, by adapting pole pitch or resolution.
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1.1.1 Rotary scales
BOGEN can produce rotary scales for many application areas. BOGEN can produce rotary scales on the flange, outer or inner diameter.
BOGEN produces rotary scales from 3 mm to 2.1 m outer diameter.
BOGEN produces rotary scales as true angular divisions. At a circumference of 360 mm and a number of 360 poles the universal magnetizing tool from BOGEN writes a north or south pole for each mm equaling exact 1°. There is no gap or mating place at any point of the scale.
The BOGEN magnetization process allows for several tracks and pole lengths from a minimum of 0. 1 mm. Scales can be produced for high accuracies up to <0,005°. For such high accuracies, the eccentricity errors of the scale need to minimized.
Due to the digital creation of the scale pattern, only a low programming fee instead of high tooling costs for magnetizing tools is required enabling engineers to experiment with different pole patterns.
Rotational scale accuracy
Using a flexible manufacturing process BOGEN offers scales for arbitrary lengths with different pole lengths. BOGEN uses different accuracy classes for rotary scales
- G006 +/- 6 arc seconds maximum deviation of a pole boundary of the ideal position
- G010 +/- 10 arc seconds maximum deviation of a pole boundary of the ideal position
- G060 +/- 60 arc seconds maximum deviation of a pole boundary of the ideal position
- G100 +/- 100 arc seconds maximum deviation of a pole boundary of the ideal position
- G600 +/- 600 arc seconds maximum deviation of a pole boundary of the ideal position
Rotary scale material
BOGEN uses different materials for rotational scales
- Ferrite ring – Using a sintered ferrite ring, BOGEN can magnetize many different patterns on the ring. While ferrite is cheap, once a tool is created, the accuracy of the ferrite is limited. Typically, the magnetized face has been ground before magnetization.
- Ferrite ring on a hub – The ferrite ring is glued on a hub to provide a more accurate positioning of the scale.
- Plastoferrite ring – Using plastics filled with ferrite, BOGEN can magnetize different patterns. Due to the production process, the accuracy of the rings is more limited than with other materials. Due to high tool costs, this material is only relevant for higher volumes.
- Elastomer on a hub – Gluing a ferrite filled elastomer on a hub enables many geometries and different scale width on a big variety of hubs. This method can be used for prototypes and scales well for high volume production.
- Vulcanized rubber on a hub – For harshest applications, vulcanizing ferrite filled rubber on a hub provides the best environmental performance while having high costs. Industrial and automotive applications are typically using vulcanized rubber.
BOGEN produces rotary magnetic scales with one or more tracks. A reference point or index can be written in the second track, which is used as the zero point for the control.
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Or contact BOGEN to get professional advice how to engineer the best possible rotary magnetic solution.