A mixing bin for the blending of materials (e.g., pharmaceuticals, foodstuffs, etc.) bears a spectrometer which monitors the characteristics of the material being tumbled within the bin interior to thereby obtain an indication of the degree to which the material is mixed. An accelerometer also rides on the mixing bin with the spectrometer, and it monitors the position of the mixing bin as it rotates. The accelerometer measurements can then be used to trigger the taking and/or recordation of spectrometer measurements at times during which the material within the bin falls against the spectrometer's input window, thereby promoting greater accuracy in spectrometer measurements, and/or at the same bin position, thereby promoting greater uniformity between spectrometer measurements.