Ultraviolet recorders are generally electromechanical Oscillographic recorders.  This is a modified version of Doodle's oscillograph.  This recorder consists of several galvanometer elements or moving coils which are housed in a single magnet block.  The ultraviolet recorder is shown in Figure. 

The Doodle Multichannel Oscillograph uses a separate magnet assembly for each galvanometer element.  Ultraviolet recorder is bigger in size and cost more.  Ultraviolet light is used as the source in the galvanometer which gives white light.

Ultraviolet recorder | Working & diagrams And applications
Ultraviolet recorder 

Paper sensitive to ultraviolet light is used for the purpose of producing traces in the recording.  Ultraviolet light is projected onto the paper with the help of mirrors attached to the moving coil. 

Working Method - When current is passed through a moving coil in an ultraviolet recorder, it gets deflected into the magnetic field of a permanent magnet.  As soon as ultraviolet light is incident on the mirror, the mirror deflects it.  With the help of lens and mirror system, this light is reflected or reflected on the ultraviolet light sensitive paper.  The paper is moved forward along with the moving light spot.  Changes occur in the trace relative to time and with current.  In most ultraviolet recorders, the appropriate paper driving speed is selected based on 12 different speeds.  Some galvanometers require an external applied voltage to control the paper speed.  Ultraviolet sensitive paper is used for photocopying and photo making. 

Using Ultraviolet Recorder  and D.C.  It is used in a signal whose fundamental frequency ranges from 400 to 500 Hz.  Frequency range depends on recorder and paper driving speed.  High-frequency input is possible for recording in an ultraviolet recorder, but the paper speed should be around 10 m/s.

Applications - Various applications of ultraviolet recorder are for 

  1.  Output of transducer, 
  2. Control system performance,  
  3. Regulation transient of generator, 
  4. Recording magnitude of low frequency signal.