Hey there folks I am trying to gain a more technical understanding of dynos and how they really work. When measuring the power at the wheels of a vehicle there are really two variables being measured: Torque and rotational speed of the roller. I have read on the different methods of controlling the torque. Now I need to clear up some things: How does a dynamometer actually measure the a) Torque and b) Rotational speed? Let me clarify my question a little: I know different ways that one could measure these things; but I am hoping someone with a little dyno experience can step in here and tell me how dyno manufacturers actually do measure these things. Is an encoder built in to the roller? Or a tachometer? How is the torque actually measured? Some kind of load cell? Anyone know of a specific brand of Dyno that has a white paper about it that I could read? (Yes. Google is working, but I am still looking for more technical writings.) Any thoughts? EDIT: After much Googling, I am thinking that a tachometer and load cell are used for the measurements. However, the load-cell reference that I came across was in a patent filing that was never granted; so that is hardly a reliable source. I am looking for some concrete instances of a particular kind of transducer being used on practice.