231-E023

Check encoder cable connections

Power down the control. Inspect the B-channel encoder cable connections at both the encoder head and the CC drive module input connector specified by parameter %5. Ensure locking mechanisms are fully engaged and pins are not bent or corroded.

Always disconnect power before checking encoder connections to prevent damage to drive inputs.

Verify encoder signal quality

Navigate to Diagnostic → TNC Scope, configure to monitor the B-channel encoder signals (typically labeled as encoder 2 or secondary encoder for the axis %2). Manually move the axis and verify clean square wave signals with proper amplitude (typically 1Vpp for 1Vpp encoders or proper TTL levels).

Set the Scope trigger to capture signal dropouts during movement. B-channel signal amplitude below 0.6Vpp on analog encoders often causes probe input errors.

Review dynamic test parameters

Access MOD function → System Parameters → CC Configuration → Dynamic Test Parameters. Verify the test speed and acceleration values are within the encoder's specified maximum velocity. Reduce test dynamics by 30-50% and retry the dynamic test sequence.

Default dynamic tests run at high speeds. Older or lower-grade encoders may lose signal integrity above certain velocities, especially if cable length exceeds 50 meters.

Test with encoder swap if available

If the machine has multiple axes with identical encoder types, temporarily swap the B-channel encoder cable with a known-good axis encoder. Retry the dynamic test on axis %2. If the error follows the cable, replace it; if the error stays with the axis, suspect drive hardware.

Ensure encoder types match exactly before swapping to prevent configuration mismatches.

Access CC drive probe configuration

Enter MOD → Machine Parameters → CfgAxisPosCtrl[axis %2] → Encoder2 (B-channel). Verify parameter 'probeInputNumber' matches the physical connection and equals %5 shown in the alarm. Verify 'encoderType' matches installed hardware (EnDat, 1Vpp, TTL, etc.).

Parameter names vary slightly by TNC version. On iTNC 530, look for 'secondaryEncoderInput' parameter in the axis-specific configuration tables.

Verify probe input electrical settings

Navigate to System Parameters → CC6x Configuration → PL Input Configuration → PL Input %5. Confirm the input type (differential, single-ended, voltage level) matches the B-channel encoder specifications. For 1Vpp encoders, ensure differential input mode is selected; for TTL, ensure RS422 mode.

Incorrect electrical mode can damage encoder outputs. Verify encoder datasheet before changing these parameters.

Reset and reinitialize drive parameters

After verifying configuration, select MOD → CC Drive Functions → Initialize Drive Parameters for axis %2. This reloads all probe input settings to the drive. Then execute MOD → CC Drive Functions → Static Test before reattempting the dynamic test.

Always run the static test successfully before dynamic tests. Static tests verify basic encoder connectivity without motion.

Inspect encoder cable routing

Physically trace the B-channel encoder cable from the encoder to the CC drive module. Ensure it is routed separately from power cables, motor cables, and VFD wiring. Minimum separation should be 200mm for parallel runs. Verify the cable is properly shielded and shield is grounded at the drive end only.

Encoder cables running in cable carriers with servo motor cables are a common EMI source. Relocate encoder cables to a separate carrier section if possible.

Check grounding and shielding continuity

Use a multimeter to verify shield continuity from encoder connector to drive module ground point. Resistance should be below 1 ohm. Verify the shield is connected at the drive end only, not at both ends (which creates ground loops). Check cabinet PE grounding integrity.

Never disconnect cabinet grounding during testing. Only verify connections are tight and low-resistance.