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The IDEXX VetLab® UA™ Analyzer is a Reflectance Photometer that reads IDEXX UA Strips
Measuring Principle
The IDEXX UA test strip is placed on a sliding tray that moves the strip into the analyzer and under
the reading head. The analyzer reads the reference pad first, and then reads each of the test
pads on the strip.
The analyzer contains light-emitting diodes (LEDs) that emit light at various wavelengths.
Reading is done electro-optically, as follows:
The LED emits light of a defined wavelength onto the surface of the test pad 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 positioned directly
above the test zone. The phototransistor sends an analog electrical signal to an A/D converter,
which changes it to digital form. The microprocessor then converts this digital reading to a
relative reflectance value by referring it to a calibration standard.
Finally, the analyzer compares the reflectance value with the defined range limits (reflectance
values that are programmed into the analyzer for each parameter) and outputs a semiquantitative
result. Each test pad is read photometrically after a lead (incubation) time of about 55–65 seconds.
The entire process from start to finish takes 70 seconds.
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