Diagnosable remotely - YES
Fixable remotely - NO
Newer CPS Instruments have a Dynamic Balancing Module (DBM) which - in addition to monitoring the balance of the disc - count the actual revolutions of the disc. It does this via a small sensor mounted behind the disc, above the motor shaft, which recognises a white line painted onto the motor shaft as the disc rotates.
In practice, this means the software is able to set the spin speed more accurately than old instruments and make finer adjustments. This is why on DBM instruments the "Actual Speed" is ususally very close to the "Set Speed", but does not match perfectly.
Sometimes, a fault occurs where the actual speed of the disc "drifts" above and below the set speed. There is an acceptable tolerance built into the software, and if the actual speed drifts too far away from the set speed, the "Operate Analyser" button - which is used to start measurements and collect data - becomes "greyed out" and cannot be accessed until the measured speed is closer to the set speed.
SOLUTION
Requires a site visit from an engineer. The most likely cause of this is that the motor shaft and/or the "white mark" on it have become scratched or discoloured. The sensor relies on a stark contrast between the black motor shaft and the white mark.
When on site, the motor shaft should be "blackened" using a thick permenant black marker all around the circumference of the motor shaft in line with the DBM sensor.
If the white paint mark is damaged, this should be patched up using TipEx to recreate the strong contrast between black and white.
In addition, if the customer is on an older software version (v11c-v11h) it can be updated to the latest version (v11n1 as of Feb '22). Later software versions have wider tolerances for the speed fluctuations. It is recommended to consult Merijn at Inventech before doing this.
If this does not solve the issue, consult with CPS/Inventech as the instrument may require a hardware replacement.