Z1 instruments incorporate a unique, new oil displacement pump which delivers a high degree of accuracy and precision, and eliminates the need for mercury utilized in the traditional mercury manometers. The Beckman Coulter Z1 Dual Cell and Particle Counter was specifically designed for simple operation. Enter the cell size (diameter or volume) and press START. The count is completed in seconds. Clear messages on the LCD display lead you through all set-up and analyses functions. Calibration requires only several keystrokes; optimum instrument settings are automatically computed and set. The constant current feature of the Beckman Coulter Z1 Dual Cell and Particle Counter eliminates calibration drift due to changes in electrolyte conductivity and temperature, a very common problem with other instruments.