Okuma OSP codes
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Okuma OSP Controller

Servo/Axis · Intermediate

Alarm 1121

Okuma OSP Alarm A 1121 - PSC Optical scale encoder error

The position encoder of the optical scale reported an error. The code distinguishes between a mismatch with the J-type encoder, simultaneous A-phase and B-phase pulse changes, and wrong signal amplitude, all of which point to a failing scale or its cable.

Okuma OSPServo/AxisIntermediate

1121

Okuma OSP Alarm A 1121 - PSC Optical scale encoder error

PSC Optical scale encoder error

The position encoder of the optical scale reported an error. The code distinguishes between a mismatch with the J-type encoder, simultaneous A-phase and B-phase pulse changes, and wrong signal amplitude, all of which point to a failing scale or its cable.

Common Causes

  • Breakdown of the optical scale itself
  • Breakdown or damage of the optical scale cable
  • Contamination on the scale tape or readhead causing amplitude errors

Troubleshooting Steps

  1. 1Read the code number shown with the alarm: code XX bit1 = J-type encoder and optical scale values too different by a negative sign; code XX bit0 = J-type encoder and optical scale values too different by a positive sign; code YY bit0 = A-phase pulse and B-phase pulse changed at the same time; code ZZ bit1 = B-phase amplitude wrong; code ZZ bit0 = A-phase amplitude wrong
  2. 2Read the code: the XX bits tell whether the J-type encoder and optical scale values are too different (bit1 negative sign, bit0 positive sign), YY bit0 means A-phase and B-phase pulses changed at the same time, and ZZ bit1/bit0 mean wrong amplitude on the B-phase or A-phase.
  3. 3Lock out power and inspect the optical scale cable from readhead to control for crushing, sharp bends, or coolant ingress; exchange the cable if damaged, as the manual directs.
  4. 4Clean the scale tape and readhead window with the approved cleaner; contamination is a common cause of wrong amplitude.
  5. 5Check the readhead mounting for looseness or a changed gap after a crash.
  6. 6If errors persist after cable exchange and cleaning, exchange the optical scale per the manual.

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