Magnetic Linear Encoders – Tape Magnetization Technology

bmlPrecision Tape Magnetization Leads to Precision Position Measurement

The key to ultimate accuracy for any magnetic linear encoder system is the precision of the magnetic encoding on the tape (sometimes called a scale). Sensors inside the encoder read head respond to the strength and position of the magnetic flux coming from the magnetic poles encoded onto the tape. Precise placement of these poles – and just as importantly, the precise shape of these poles – is critical to the ultimate level of accuracy that can be delivered by the encoder system. Any inaccuracy in the position, strength, or shape of these fields will directly influence the accuracy of the encoder’s indicated position. This effect is amplified with increasing gap distance between the tape and the encoder read head. The further away from the tape, the weaker and more indistinct the shape and position of the magnetic poles becomes.

Not All Magnetic Tapes Are Created Equal

Many magnetic encoder tapes on the market are surface magnetized utilizing the conventional parallel magnetization process. This is a straightforward technique that results in an encoder tape that meets performance specifications at close gap settings between the read head and the tape.

A more recent tape magnetization process called Permagnet® produces magnetic poles with improved control over their strength, shape, and location on the tape. The best way to appreciate the advantages of this technology is to compare magnetic scans of some conventionally magnetized tapes to some examples of tapes encoded with the Permagnet® process. Note the visible difference in sharp definition of the magnetic poles that is produced by the newer technology.

Conventionally Magnetized Tape – Sample #1

Sample #1 - Conventionally magnetized tape: 2 mm pole spacing, scanned at a distance of 0.2mm from the tape surface

Sample #1 – Conventionally magnetized tape: 2 mm pole spacing, scanned at a distance of 0.2 mm from the tape surface

Sample #1 - Conventionally magnetized tape: 2mm pole spacing, scanned at a distance of 0.8 mm from the tape surface

Sample #1 – Conventionally magnetized tape: 2 mm pole spacing, scanned at a distance of 0.8 mm from the tape surface

Tape Magnetization with Permagnet® Technology – Sample #2

Sample #2 - Permagnet tape: 2mm pole spacing, scanned at a distance of 0.2 mm from the tape surface

Sample #2 – Permagnet tape: 2mm pole spacing, scanned at a distance of 0.2 mm from the tape surface

Sample #2 – Permagnet® tape: 2 mm pole spacing, scanned at a distance of 0.8 mm from the tape surface.

Sample #2 – Permagnet® tape: 2 mm pole spacing, scanned at a distance of 0.8 mm from the tape surface.

The stronger, more sharply-defined magnetic poles produced by Permagnet® technology enables encoders to be more tolerant of variation in the working distance between the encoder read head and the tape. Reduced dispersion and distortion of the magnetic fields at any distance within the specified working range reduces the influence of distance variation on the accuracy of the position measurement in real-world applications.

Summary of Application Benefits

  • Improved linearity at close working distances for ultimate system accuracy
  • Improved linearity at longer working distances
  • Higher tolerance to deviations in the working distance, with reduced non-linearity
  • Less need to closely control the working distance in the application, saving cost by reducing painstaking setup and alignment effort
  • Full system accuracy, even if gap distance varies during operation
  • Better linearity for any given pole spacing on the tape

About Henry Menke

I have an electrical engineering background that provides me with a solid technical foundation for my current role as Marketing Manager.
This entry was posted in All posts, Linear Position and Distance Measurement and tagged , , , , , . Bookmark the permalink.

What do you think?

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s