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For detailed troubleshooting of the PH20 system please refer to the CMM support knowledgebase ( or contact your local Renishaw office.

PH20 system status indicator LEDs

The head incorporates two LEDs for status indication in various modes, located as illustrated below.

PH20 head LEDs


 Servo LED

 Probe LED


 No power (probe LED also off)

 Probe triggered or module removed


 Servos on

 Probe seated


 Servos off

 Probe inhibited

 Flashing red

 Power,  no comms



 'Soft engage' mode*


* The ‘Soft engage' is a fault condition where the PH20 head uses a weak motor drive and can be manually rotated to prevent damage.

Head comms signal booster box indicator LEDs

PH20 booster box LED labels

There are three LEDs on the head comms signal booster box that can be used for basic fault indication.






 No system power
 HCSB not connected to UCC or UCC powered down

 No comms from UCC
 Downloadable isn't running
 Check cable and system software

 No comms from head and / or UCC or downloadable isn't running
 Check cable and check system software


 Normal operation



 Flashing green


 Comms OK from UCC

 Comms OK from head

 Flashing red


 Comms error from UCC - check cable to UCC

 Comms error from head - check cable to head