A New High Speed Inkless Recorder

A portable instrument is described for recording level changes or low frequency wave forms on a 2‐inch wide strip chart. A novel servo system, employing a power driven stylus, is utilized, giving a greater force‐to‐mass ratio than has heretofore been possible. Recording speeds in excess of 1000 db per second on a logarithmic db scale are attainable, with a continuously variable stylus‐speed control. A novel feed‐back loop used in conjunction with antihunt circuits makes possible very rapid stylus movement insuring maximum accuracy and stability. Eight synchronous chart speeds from 1 to 200 mm/sec. are push‐button selected for accurate time axis recording. A take‐up chart spindle is provided for continuous recording. Especially designed for acoustic reverberation studies, it provides accurate means for investigating low reverberant chambers of 0.1 second, and less, reverberation time.