A Less Expensive Magnetic Linear Encoder
I haven’t found the linear encoder promised land I was looking for, but recently I did learn a bit about some reasonably priced linear encoders: Turck’s LI20 and LI50 hall effect based magnetic linear encoders.
The LI20 is available with 10 micron resolution, and handles speeds up to 25 m/sec.Â The LI50 is available with 5 micron resolution and speeds up to 16.25 m/sec (although at 5 microns, max speed is about 3 m/sec).
If I have my part numbers and PLC Center pricing correct, a T8.LI20.1111.2050 with 1 meter encoder strip (magnetic band) would be about $315, and a T8.I.LI50.1111.2250 with a 1 meter encoder strip would be about $430.Â (For the magnetic band, I’m assuming buying 90 m (T8.B1.10.010.0900 or T8.B2.10.010.0900) and cutting into 90 pieces each 1 m long; it looks buying shorter lengths is considerably more expensive per meter).
Note 5/10/2010: Honeywell also makes affordable magnetorestrictive linear encoders, although I don’t think they are well suited for typical industrial automation applications.Â Minimum resolution is 140 microns, length is 75 or 225 mm, and output is analog or RS-232 (225mm only).Â The SPS-L225-HALS (225mm analog) is about $250.