CDA Systems' DC motor speed modules measure the speed of a DC electric motor based on the ripple in the motor's supply current. No physical contact or line of sight is required.
These modules allow for test of correct installation and/or operation of motor embedded inside the end product.
There are several benefits to utilizing motor current waveforms for speed tracking. The obvious case is where there is no line of sight to a moving part from which to sense the speed, but there are other reasons:
Advantages of DC Motor Speed Sensing via Motor Current