Question

A position sensor is used in a microprocessor-based feedback control system for accurately moving the cutter blades of an automated meat-cutting machine. The machine is an integral part of the production line of a meat processing plant. What are primary considerations in selecting the position sensor for this application? Discuss advantages and disadvantages of using an optical encoder in comparison to a LVDT in this context.

Answer 1

In optical encoders, a source shines light through or on to a rotating disk, which is marked so that the light is blocked or travels through. The optical sensor senses the passage of the light and then produces a corresponding electrical pulse.

By the arranging the optical scales as a series of markings, the angle or motion can be measured. The scale of the markings can be extremely fine – down to microns.

Advantages of an optical Encoder
- Highly reliable and accurate
- Low-cost feedback
- High resolution
- Integrated electronics
- Fuses optical and digital technology
- Can be incorporated into existing applications
- Compact size

Disadvantages of an Encoder
- Subject to EM magnetic or radio interference.
- Direct light source interference.
- Susceptible to dirt, oil and dust contaminates.