the digital pressure gauge system is particularly useful for reading blood pressures of humans , and has general utility in dial or disc type gauges for reading liquid and gas pressures . the digital pressure gauge system includes a rotary encoder which takes the place of the dial or disc of a conventional pressure gauge and therefore rotates to a degree proportional to the magnitude of the pressure being read . the rotary encoder carries a plurality of light sources which are selectively located for encoding particular angular positions of the rotary encoder . these light sources selectively direct light on photosensors which are connected by circuitry to digital readouts for converting the encoded information into a digital display . the displays may be contained in the gauge unit or they may be located remotely from the gauge unit if desired .