The first patent for the idea was filed in 1949 with the US Patent Office and issued in 1953 to American electrical engineer Wallace Coulter who was conducting research into the field with his brother Joseph Coulter. The voltage pulses provide insight into the volume of cells passing through in the suspension.

For example, there may be a drop in current as a molecule passes through the aperture because the molecule is less conductive than the surrounding electrolyte.

The count is achieved by observing the changes in voltage detected as either a cell or electrolyte travels through the aperture. With a Coulter Counter, an electrolyte containing the cells travels through a small aperture that is connected to an electric current. They are also useful for counting other types of cells such as bacteria, fat, muscle, and other types of cells. The instruments are commonly found in hospitals to help the medical staff determine the cell count of a patient’s blood sample – the ‘Complete Blood Count’. A Coulter Counter is able to count the erythrocytes (red blood cells), leukocytes (white blood cells), and platelets. High or low cell blood counts are significant in identifying diseases. For example, the number of cells of a certain type in a blood sample can provide clues to the type of disease that a patient is suffering. A Coulter Counter is an instrument that can count and size the cells in an electrolyte to provide valuable information for researchers.

Beckman coulter cell counter