ExpainCounting Instruments 2 Major Principles: 1. Electrical Impedance Analyzes the resistance created by each cell passing through an electrical field Coulter principle - increased resistance occurs when poorly conductive blood cells pass through aperture. Ex: Abbott Diagnostics, Beckman Coulter Inc., and Sysmex Corporation 2. Optical Light Scatter Analyzes the scatter of light (forward and side) detected by each cell passing through a beam of light (optical or laser) Ex: Siemens Healthcare, Sysmex Corporation, and Abbott Diagnostics