AdvancedMedium risk

Encoder feedback fault (position/speed wrong)

Position or speed feedback from an encoder is wrong — counts drift, position is lost, or a drive faults on encoder loss, so motion control misbehaves.

Start fault-finding

Safety first

Loss of position/speed feedback can cause unexpected motion. Ensure the axis is safe and clear before testing. Isolate before handling encoder wiring.

Isolate, lock out / tag out, and prove dead before working unless a live test is specifically required, authorised, and carried out under proper supervision. Always follow local regulations, your site procedures, and the equipment manufacturer's documentation.

Full detail — causes, the why, and common mistakes.

Likely causes

Ranked from most to least likely.

1
Encoder cable/connector fault
Most likely
A damaged, chafed, or loose encoder cable corrupts the feedback signals — common on moving axes.
2
Electrical noise on the feedback
#2
Poor screening/earthing lets noise corrupt the counts, causing drift or loss.
3
Coupling slipping on the shaft
#3
A loose encoder coupling slips, so feedback doesn't match real movement.
4
Failed encoder
#4
The encoder itself has failed or is producing bad signals.
5
Drive/controller encoder config wrong
Least likely
Wrong PPR, type, or input setup makes good signals read incorrectly.

Reports are saved on this device to reflect what you actually find.

Premium fault tree

The full ranked causes, test sequence and flowchart for this fault are part of Sparkie Sidekick Pro.

Coming soon — no payment required during preview.

Testing sequence

Work through one test at a time. Expected reading and what each result means.

Test 1 of 3

Check the encoder cable and connector along its run and at both ends (especially on moving parts).

Expected reading

Intact, secure cable and clean connectors.

Your actual reading

If it passes

Cabling sound — check coupling and configuration.

If it fails

Damaged/loose cable or connector — repair/replace.

Often leads toSensor intermittent / drops out randomly Analogue sensor (4-20mA / 0-10V) reading wrong

View all expected readings at once

1. Check the encoder cable and connector along its run and at both ends (especially on moving parts).

Intact, secure cable and clean connectors.

2. Confirm the encoder coupling is tight and turning exactly with the shaft (no slip).

No slip between encoder and shaft.

3. Verify the drive/controller encoder configuration (type, PPR, direction) and check signal quality/screening.

Config matches the encoder; clean screened signals.

Full test sequence

The step-by-step test flow with expected readings for this fault is part of Sparkie Sidekick Pro.

Coming soon — no payment required during preview.

Fault-finding flowchart

The same logic as a decision tree.

1
start
Encoder feedback fault
→ step 2
2
decision
Is the encoder cable/connector intact and secure?
Yes→ step 3No→ step 4
3
decision
Is the coupling tight (no slip)?
Yes→ step 5No→ step 6
4
result
Damaged/loose cable or connector — repair/replace.
5
decision
Is the config correct and signal clean/screened?
Yes→ step 7No→ step 8
6
result
Slipping coupling — secure it.
7
result
Suspect a failing encoder — replace and re-test.
8
result
Wrong config or noise — correct config / improve screening & earthing.

Common mistakes apprentices make

Replacing the encoder before checking the cable on a moving axis.
Ignoring screening/earthing and chasing intermittent count errors.
Missing a slipping coupling.
Wrong PPR or encoder type in the controller config.

When to stop & escalate

Persistent noise problems may need a cabling/earthing review. Configuration changes on motion systems should follow the machine's commissioning data; back up before changing.

If you're past your competence, authorisation, or the safe limits of the job — stop and hand it on. There's no fault worth getting hurt over.

Related faults

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5 causes3 test steps

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VSDs

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Learn the theory

How the gear and circuits behind this fault actually work.

Device

Encoder

Gives precise position or speed feedback by producing pulses (or a coded value) as a shaft turns.