Here I gloss over and demonstrate measuring the M260 DC Motor in the SparkFun Inventor's Kit with the included photoresistor and a multimeter. The two parts were recorded months apart, so please bear with any continuity quirks (e.g. I grow a beard mid-video). The last third of part II simply demonstrates measurements using a break-beam concept; the rest is about reflecting light. There is quite a bit more video where I ramble on about the many ways to measure speed (and torque), but I chose to cut it out.

• DC Motor Speed Part 1: https://goo.gl/Ah7udS (YouTube)
• DC Motor Speed Part 2: https://goo.gl/8Gm2EY (YouTube)

My mid-range multimeter, an Extech EX330, was not capable of measuring the frequency of the generated signal, but my professional meter, a Fluke 87V, was able to measure it. (The low-end oscilloscope also measured the frequency, but I stayed away from using it in this video for direct results, instead concentrating on demonstrating the use of more common equipment.)