A method for calibrating a contaminant detection device includes fluidly connecting the contaminant detection device in series to a test reservoir and a light-obscuration-type particle counter, pumping low-end, intermediate, and high-end test dust dilutions through the contaminant detection device and the particle counter until a particle count measured by the particle counter for each of the successive test dust dilutions stabilizes, and setting a low-end gain, an intermediate gain, and a high-end gain for the contaminant detection device based on the stabilized particle counts for each of the test dust dilutions using a first-sized test dust grade. A bubble counting gain of an aeration threshold for the device may be set according to a second test dust grade greater in size than the first-sized test dust grade, and associated with a voltage signal produced by the contaminate detection device indicative of the presence of an air bubble contained within the fluid during use of the fluid in heavy machinery.