Scott Beversdorf and Chuck Whiting
Analog Devices

A solenoid is a linear motor with a fixed range of travel. Solenoids may be designed for simple on-off applications, acting much like relays. For example, they are used this way in starters and door locks. On the other hand, a linear, or proportional, solenoid is one whose position can be controlled in a precise manner. They are used to operate pistons and valves for accurate control of fluid pressure or flow in applications such as transmissions and fuel injection. this article provides an introduction to current measurement in solenoids for automotive control systems.