41. The galvanometer is constructed as a number of moving-iron galvanometers , sharing the same excitation coil. 42. Have I misunderstood, is there an implicit resistor, not on the diagram, protecting the galvanometer ? 43. Crookes had Fay hold two electrodes in an electrical circuit connected with a galvanometer in an adjoining room. 44. There she built galvanometers , a device that detects electrical currents and is used to help geologists locate oil. 45. A moving coil galvanometer can be used as a voltmeter by inserting a resistor in series with the instrument. 46. He patented the key elements of his system, the mirror galvanometer and the siphon recorder, in 1858. 47. A tangent galvanometer consists of a coil of insulated copper wire wound on a circular non-magnetic frame. 48. {{ cquote | The mirror galvanometer consists of a long fine coil of silk-covered copper wire. 49. Each of the two flat or polygonal mirrors is then driven by a galvanometer or by an electric motor. 50. The direction of travel was read by comparing the indications on two independent galvanometers , one for each armature.
