The ‘Edspot’ is a very sensitive long range galvanometer, used to detect direct current flow. Because of the very sensitive nature of the Edspot, it is very useful in detecting the very small currents that flow when experimenting with electromagnetic induction. In this case, a coil of wire is connected to the Edspot’s front connectors and a bar magnet is then pushed through the coil. A small current will flow through the wire which can be read from the illuminated scale. The Edspot takes the place of a microammeter in this case as it is far more sensitive.
The Edspot contains a moving mirror instead of a pointer and as such is known as a light beam galvanometer, this different approach helps to make the device incredibly sensitive
The scale can be centred using the knob on the front of the device. The other dial adjusts the sensitivity and should be set to suit the application the Edspot is being used for. There are several settings here including ‘direct’
(where the scale is free to swing) and ‘short’ which applies heavy damping to the mechanics. This is the setting you should select when moving the device to prevent damage.
Edspot galvanometers are fairly expensive (around £600) and delicate. Care should be taken when moving and connecting the device, ensuring you do not connect it directly to a high voltage/current power supply where it may be irreparably damaged. Many schools allow only staff use of the Edspot. In electromagnetic induction class practicals, pupils can use the less expensive and slightly less delicate milliammeters or millivoltmeters.