Coulter counter
（重定向自Coulter principle）
![Coulter Principle — the transient current drop is proportional to the particle volume.](/Images/godic/202501/06/Particle_Transit_Channel2049.gif")
![The tip of the Coulter counter in a buffer solution, counting cells in solution.](/Images/godic/202501/06/Coultercounter2049.jpg")
![Coulter patented several different implementations of the Coulter Principle. Image taken from US Patent #2,656,508.](/Images/godic/202501/06/Coulter_geometries2050.png")
![Model A Coulter Counter - The First Commercial COULTER COUNTER](/Images/godic/202501/06/Model_A_COULTER_COUNTER_from_Advertisement2050.jpg")
A Coulter counter is an apparatus for counting and sizing particles suspended in electrolytes. It is used for cells, bacteria, prokaryotic cells and virus particles.
A typical Coulter counter has one or more microchannels that separate two chambers containing electrolyte solutions. As fluid containing particles or cells is drawn through each microchannel, each particle causes a brief change to the electrical resistance of the liquid. The counter detects these changes in electrical resistance.