System Description; Measuring Principle - cobas Urisys 1100 Manual De Instrucciones

2. System Description

2.1

Measuring Principle

The test strip is placed on a sliding tray, and a stepping motor moves it under the reading head, which remains stationary.
The ana lyzer reads the reference pad, followed by each of the test pads on the strip.
The reading head contains LEDs that emit light at various wavelengths. Reading is done electro-optically, as follows:
3 5
4
1
6
2
The LED (1) emits light of a defined wavelength on to the surface of the test pad (2) at an optimum angle. The light hitting
the test zone is reflected more or less intensely depending on the color produced on the test pad, and is picked up by the
detector, a phototransistor (3) positioned directly above the test zone. The phototransistor sends an analogue electrical sig-
nal to an A/D converter (4), which changes it to digital form. The microprocessor (5) then converts this digital reading to a
relative reflectance value by referring it to a calibration standard.
Finally, the system compares the reflectance value with the defined range limits (reflectance values that are programmed
into the analyzer for each parameter) and outputs a semi-quantitative result (6).
Each test pad is read photometrically after a lead (incubation) time of about 55–65 seconds. In strongly alkaline urine sam-
ples, the Urisys 1100 system automatically corrects the result of the Specific Gravity test.
Gebrauchsanweisung V04 / Operator's Manual V04 / Manual de instrucciones V04 31