or I = K tan θ, where K is called the Reduction Factor of the tangent galvanometer.
One problem with the tangent galvanometer is that its resolution degrades at both high currents and low currents. The maximum resolution is obtained when the value of θ is 45°. When the value of θ is close to 0° or 90°, a large percentage change in the current will only move the needle a few degrees.[citation needed]
Geomagnetic field measurement