Integral subtraction differentiator

摘要

A differentiation signal is generated by a subtractor 203 that subtracts a mathematical integral of an original signal generated by an integral module 201 from the original signal. The differentiation signal can contain less high frequency noise than a mathematical derivative of the original signal. The original signal can be a voltage representing either the current through or the voltage across a solenoid coil such as a fuel-injector, as a function of time and be used to detect an end of motion of an armature. Integral module 201 can comprise an integrator or a low-pass filter having an optimised time constant. Subtractor 203 can comprise a differential amplifier that applies gain to the difference signal.