2.1.1. Counting chambers with electrodes and measuring apertures
Impedance method is used for determination of volume and number of cells. In this method
a known volume of dilution is drawn through a small aperture. Constant current is passed
through the aperture from one side to the other. When a cell passes through the aperture, it
causes a change in resistance, which generates a voltage pulse.
The amplitude of the voltage pulse is proportional to the ratio of cell volume per aperture
volume. This is used to determine the volume of cells. The number of cells can be obtained
by counting the pulses.
perture, and
-shaped
metal fixing as it is shown in the next figure.
The aperture is made of ruby and it is moulded into the measuring tube.
2.1.2. HGB Head
Hemoglobin head is placed on the two sides of the WBC chamber.
It contains: light source (LED) at 540 nm wavelength and Photo Detector (TSL235). The
Photo Detector converts the light to frequency. The HGB concentration is a logarithmic
function of this frequency measured by the FPGA circuit of the COMB card.
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