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Encoders vs. Resolvers
| How are
incremental encoders different
than resolvers? |
| Output Signal |
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Encoders
produce
pulses indicating movement over a short distance; counting these
pulses indicates distance (and speed over time) and checking the order
of pulses in channel A vs. channel B indicates direction (quadrature). |

Resolvers
produce a set of sine/cosine waves (analog voltage) indicating absolute
position within a single revolution; these signals are typically
converted with a resolver interface board to a digital signal. |
| Input Signal |
|

Encoders are typically powered with simple DC voltage. |

Resolvers are “excited” by an AC sine wave, typically created with a
dedicated resolver power supply; this power supply is typically powered
with simple DC voltage. |
| Location of Electronics |
|

Encoders typically have all their electronics onboard, minimizing
interconnections, but limiting operating temperatures. |

Resolver systems typically mount the resolver power supply and resolver
interface board near the input device, requiring substantial inter-device
wiring, but allowing the resolver to withstand higher temperature
environments. |
| Can I replace a resolver with an encoder? |
| For existing installations,
encoders can
only replace resolvers if the input device (drive, PLC, etc.) can accept
encoder quadrature input signals as an alternative to resolver input. |
| For new installations,
encoders can replace all resolvers, unless the
environment is below -40°F/-40°C or above 212°F/100°C ambient, or the input
device cannot accept encoder signals. |
| Virtually all modern AC and DC drives can use
encoders for feedback; very
few can use resolvers. |
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