Efficiency: The ratio of power output to power input.

Electrical Time Constant: The ratio of armature inductance to armature resistance.

Electrohydraulic Servo Valve: A directional type valve which receives a variable or controlled electrical signal and which controls or meters hydraulic flow.

Electromagnetic Interference(EMI): A modification of signal contained in circuit wiring (or stored in a microprocessor) caused by a strong magnetic field radiated from some other electrical or electronic device or conductor.

Electromotive Force (EMF): The force produced by a difference of electrical potential that causes current to flow in a circuit. EMF is measured in units called volts.

Energy: The ability or capacity to do work. Measured in units of work.

Enclosure: A rectangle drawn around a graphical component or components to indicate the limits of an assembly.

Encoder: A device that translates mechanical motion into electronic signals used for monitoring position or velocity.

Error (Signal): The signal which is the algebric summation of a command signal and a feedback signal.