A method of operation of a fluid dispenser, the fluid dispenser comprising: a fluid containing reservoir, a dispensing mechanism which on activation causes fluid to be discharged from the from the reservoir, an activation mechanism for activation of the dispensing mechanism by movement of the activation mechanism, the activation mechanism adapted for engagement by a user to move the activation mechanism, an electrical generator for generating electrical energy, the electrical generator coupled to the activation mechanism such that on movement of the activation mechanism, the electrical generator generates electrical energy, the method comprising the step of: (a) moving the activation mechanism by the user to discharge fluid with the dispenser and to generate electrical energy with the electrical generator: characterized by the method including the steps of: (b) measuring at least one feature of the energy generated to produce a measured result, which feature is selected from the group consisting of a feature of the current of the energy generated, a feature of the voltage of the energy generated, a feature of the energy generated and combinations thereof, and (c) estimating as a function of said measured result for the feature an estimated amount of fluid discharged, wherein for a given each step (a) carrying out step (b) to produce the measured result for step (a) and then carrying out a step (c) to estimate an estimated amount of fluid discharged for the given step (a), and a step (d) of comparing the estimated amount of fluid discharged for the given step (a) to a predetermined minimum dose volume, and providing a fluid discharged signal indicative of whether the estimated amount of fluid discharged for the given step (a) is: (i) less than the predetermined minimum dose volume or (ii) at least equal to the predetermined minimum dose volume. a fluid containing reservoir, a dispensing mechanism which on activation causes fluid to be discharged from the from the reservoir, an activation mechanism for activation of the dispensing mechanism by movement of the activation mechanism, the activation mechanism adapted for engagement by a user to move the activation mechanism, an electrical generator for generating electrical energy, the electrical generator coupled to the activation mechanism such that on movement of the activation mechanism, the electrical generator generates electrical energy, the method comprising the step of: (a) moving the activation mechanism by the user to discharge fluid with the dispenser and to generate electrical energy with the electrical generator: (a) moving the activation mechanism by the user to discharge fluid with the dispenser and to generate electrical energy with the electrical generator: characterized by the method including the steps of: (b) measuring at least one feature of the energy generated to produce a measured result, which feature is selected from the group consisting of a feature of the current of the energy generated, a feature of the voltage of the energy generated, a feature of the energy generated and combinations thereof, and (c) estimating as a function of said measured result for the feature an estimated amount of fluid discharged, (b) measuring at least one feature of the energy generated to produce a measured result, which feature is selected from the group consisting of a feature of the current of the energy generated, a feature of the voltage of the energy generated, a feature of the energy generated and combinations thereof, and (c) estimating as a function of said measured result for the feature an estimated amount of fluid discharged, wherein for a given each step (a) carrying out step (b) to produce the measured result for step (a) and then carrying out a step (c) to estimate an estimated amount of fluid discharged for the given step (a), and a step (d) of comparing the estimated amount of fluid discharged for the given step (a) to a predetermined minimum dose volume, and providing a fluid discharged signal indicative of whether the estimated amount of fluid discharged for the given step (a) is: (i) less than the predetermined minimum dose volume or (ii) at least equal to the predetermined minimum dose volume.