Guide · 8 min read · Updated October 2026

Choosing feedback for a new servo or BLDC motor: a guide for motor makers

The feedback device decides how well a new motor will run, how it will be aligned in production and how it will be repaired in ten years. Choose the drive first, then the feedback the drive can read, then the cheapest device that meets your speed, accuracy and environment needs.

By Suresh Sankaran, founder of Star Automations, servo motor repair since 1998.

01Options

Feedback options compared

Feedback	Resolution	Strengths	Watch out for	Good fit
Hall sensors	6 states per electrical cycle	Cheap, simple, tolerant	Torque ripple at low speed; alignment of the Hall board	Fans, pumps, EV hub motors, simple BLDC
Incremental ABZ + UVW	1,000 to 10,000 lines	Widely supported, low cost	Needs homing; noise on long cables; alignment of UVW	General servo axes
Sine/cosine 1 Vpp	High after interpolation	Smooth low-speed control	Sensitive to noise and cable quality	Precision axes, spindles
Serial absolute (EnDat, Hiperface, BiSS, proprietary)	17 to 26 bits per turn	No homing, motor data in memory, few wires	Drive compatibility; memory programming in production	Modern servo motors
Resolver	Moderate	Rugged in heat, shock, coolant	Needs R/D converter; lower accuracy	Presses, high-temperature, heavy duty

02Questions

Questions to answer before you choose

Which drives must run this motor, and which feedback protocols do they accept?
What speed range and speed ripple does the application allow?
Is absolute position needed at power-up, and across multiple turns?
Battery-backed, geared or battery-free multi-turn?
Temperature, vibration, coolant and IP rating at the motor
Cable length and the number of wires available
Shaft type: tapered, hollow or coupling, and how it will be removed for service
Functional safety requirements, if any

03Production

Plan alignment and test in production

Decide early how the commutation offset will be set: mechanically by rotating the encoder, or electronically by writing an offset to the encoder memory. Electronic offset is faster and repeatable, but it needs the right tool and a record of the value for every motor.

Build an end-of-line test that checks insulation, winding balance, back-EMF, feedback counts and the offset at every pole pair, then a run test. Keep the records: they make warranty and repair much easier.

04Service

Design for repair

Use connectors and pinouts that a service shop can test without your drive
Make the encoder removable without pulling the rotor
Store the motor data in the encoder or on the nameplate
Publish the commutation reference so a repairer can verify alignment

05Help

When to send it to us

We test prototype motors and feedback on our universal test platform and can help you define an alignment and end-of-line test. Send the nameplate or WhatsApp +91 97866 22233. Related: custom motor manufacturing, BLDC driver solutions, encoder services.

Free downloads for your maintenance file

Printable one-page sheets from our bench. More on the resources page.

Motor feedback selection guide

For motor makers and machine builders: Hall sensors, incremental encoders, absolute encoders and resolvers compared on cost, resolution, temperature, noise immunity and drive compatibility.

PDF · 1 page · 4 KB · free, no sign-up

Download PDF

Servo motor encoder quick reference

Encoder families, interfaces, counts per revolution and the motors they sit on: Fanuc pulsecoders (alpha A64, A1000), Mitsubishi OBA/OSA, Yaskawa UTOPH, Tamagawa, Heidenhain ECN/EQN/ERN and SICK SKS/SRS/SRM.

PDF · 2 pages · 8 KB · free, no sign-up