A method of mass analysis and a mass spectrometer are provided wherein a batch of ions is accumulated in a mass analyzer; the batch of ions accumulated in the mass analyzer is detected using image current detection to provide a detected signal; the number of ions in the batch of ions accumulated in the mass analyzer is controlled using an algorithm based on a previous detected signal obtained using image current detection from a previous batch of ions accumulated in the mass analyzer; wherein one or more parameters of the algorithm are adjusted based on a measurement of ion current or charge obtained using an independent detector located outside of the mass analyzer.