what advantage might there be to having the encoder located on the motor side of the gearhead instead of at the output shaft of the gearhead

The definition is defined in the clarification segment following the table, as per the particular circumstance.

Explanation:

In something like a closed-loop device, shaft encoders were being used, the output of which could be influenced either by encoder location. Most motors have been used for gearbox speed reduction (RPM). Assume there's also a gearbox reduction of 30:1 as well as the motor is already spinning at a higher 3000 rpm, then the outcome feature shaft speed would be 100 rpm. This suggests that every other output shaft turning correlates to 30 input shaft flips, and even if the encoder contains 40 holes through its diameter, instead every output shaft revolution contributes to pulses. That implies an accuracy of 0.3 degrees of rotation of the final output shaft .  

Accuracy as well as reliability are thus given by positioning the encoder on the engine side instead of on the outcome shaft including its gear head.