SV0382 Count Miss (Separate Detector) fault in Fanuc drive

SV0382 Count Miss (Separate Detector) fault in Fanuc drive

Description

SV0382 is a specific digital error for machines equipped with external linear scales (Heidenhain/Fagor). It stands for "Count Miss." The drive receives serial position data from the scale. If the internal phase relationship of the signals (A-phase vs B-phase) violates the quadrature logic, or if the checksum of the data packet is invalid, SV0382 triggers. This implies the data is corrupted, usually due to signal attenuation or noise.

Cause

• Dirty Scale Glass: The most common cause. Oil or condensation on the glass scale disrupts the optical reader, causing it to "skip" a count.
• Ground Loops: Improper grounding of the scale body versus the machine casting creates electrical noise.
• Cable Length: The cable from the scale to the drive is too long, causing voltage drop and weak signals.
• Vibration: Heavy machining vibration causing the reader head to dither.

Solution

1. Clean the Scale: Use the manufacturer's recommended cleaning kit (usually air and isopropyl alcohol). Ensure the air purge system is working to keep positive pressure inside the scale.
2. Check Shielding: Verify the shield of the scale cable is clamped to the ground bar in the cabinet.
3. Bypass: To verify the fault, disable the scale in parameter 1815 (Bit 1). If the machine runs fine on the motor encoder, the scale hardware is at fault.