Month: March 2018

Oscilloscopes

The oscilloscope was developed over 50 years ago. As a piece of test equipment, it was one of the most exciting advances in electrical testing at that time and still is. Ordinary analog and digital meters merely give numerical quantities, whereas the oscilloscope does that and in addition, gives a graphic picture of what the test signal looks like. The shapes, frequencies, amplitudes, phases, distortions, interference, and so on, all show up to be examined. One cycle or less of an AC signal, or multiple cycles, or even a stream of cycles can be examined. DC levels and combinations of DC and AC can be viewed.

Every meter coil has a certain amount of dc resistance. The amount of resistance depends upon the number of turns on the coil and the size of the wire used to wind the coil. The strength of the magnetic field about a coil increases as the number of turns of the coil increases. Therefore, if more windings are placed on a meter coil, a small current can create a magnetic field strong enough to cause the coil to deflect full scale.

Scales for Moving-Coil Meters

Moving-coil meter movements have a linear scale; that is, a scale in which the space between numbers is equal. The distance that the pointer deflects across the scale is directly proportional to the amount of current flowing through the meter coil.