Ammeter, Magnifying Spring.
A solenoid ammeter in which a spiral spring is used to convert the
longitudinal motion of the armature or movable core into a rotary motion
(see Ammeter, Ayrton's) and magnify the apparent range of motion.
Ammeter, Permanent Magnet.
An ammeter with a magnetic field produced by a permanent magnet.
Ammeter, Solenoid.
An ammeter in which the attraction, when a current is passing through
it, exerted by a hollow coil of wire upon an iron bar or tube in line
with its axis, is utilized to indicate the strength of current. The bar
is drawn into the coil to different extents proportional to the
attraction. As an example see Ammeter, Ayrton's, and cut of Gravity
Ammeter.
Ammeter, Spring.
An ammeter in which the part moved by the current is controlled or
brought to the zero position by a spring.
Ammeter, Steel Yard.
A solenoid ammeter in which the solenoid core is suspended vertically
from the short end of a steel yard fitted with a sliding weight. The
current passes through the solenoid coil and attracts or draws downwards
the coil. A sliding weight is moved in and out on the long steel-yard
arm which is graduated for amperes. In use the weight is slid out until
the arm is in equipose; the divisions give the amperes.
Fig. 12. STEEL YARD AMMETER.