Counting Chambers With Electrodes And Measuring Apertures; Hgb Head - Diatron Abacus + Service Manual

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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.
In the instrument there are two Cellcounter Probes: WBC probe with 100 μm aperture, and
RBC probe with 80 μm aperture. Both have a ground electrode assembly and U-shaped
metal fixing as it is shown in the next figure.
Assembled Cell-counter Probe
Measuring tube Reference electrode
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.
LED
Measuring tubes
Connection to the amplifier
TSL235
rev 1.09
Diatron MI PLC
Red rings mark
measuring tubes:
One: RBC – 80 μm
Two: WBC – 100 μm
O-ring
U-shaped metal fixing