Example device meters disclosed herein include a signature reporter to report, to a data processor, media signatures of a first type to monitor media presented by a media device Disclosed example device meters also include a signature generator to (i) generate the media signatures of the first type, (ii) generate media signatures of a second type, different from the first type, to continue monitoring the media presented by the media device after receipt, from the data processor, of an indication that a first media signature of the first type is associated with first reference media, and (iii) in response to detection at the device meter of a change in a source of the media presented by the media device, revert to generation of the media signatures of the first type to monitor the media presented by the media device.