The Galvanometer

Figure 1. Tangent Galvanometer

Brief: The Galvanometer is a device used to detect the electric current flowing through an object. The current disrupts the magnetic field in the coil of the device. The word galvanometer was first attributed to Luigi Galvany in 1836 when he realized that the electric current would make a dead frog's leg jerk. The earliest galvanometer relied on Earth's magnetic polarity to reset the device after every use. Eventually improvements led the galvanometer to its final form as the Mirror galvanometer. This device was designed by William Thomson (Lord Kelvin) uses permanent magnets hung by a thread between a coil with a mirror affixed to the magnets. The light would bounce of the mirror onto a scale when a current would displace the magnets holding the mirror.

Figure 2. Mirror Galvanometer

The galvanometer quickly became an important toll to the medical profession because it was discovered that organic matter reacts to electricity. Additionally, the body creates its own electricity from its muscles. The most well known application of this aspect is the ECG or Electrocardiogram, where the electrical signals are plotted on a standardized form to measure a patient's heartbeat cycle. However it was found that galvanometer can measure additional muscle groups like the EMG (Electromyography) and EEG (Electroencephalogram). Overall, the galvanometer's use and application are the basis of many electromechanical control devices today.

Figure 3. Sample ECG Reader

Use: Originally the galvanometer was used to troubleshoot telecommunications cables. Additionally, they make up the basic functions for the ECG, EMG, and EEG. In more modern times they are used in positioning and control systems. This utilizes all types of galvanometers from tangent to mirrors.

Additional Information: General History, More History, General Information