Many of the instruments at Turner Designs will initially display a measurement called RFU, which stands for Raw Fluorescence Units, before the instrument is calibrated. Some examples of RFU being displayed are on our AquaFluor Handheld Fluorometers and Trilogy Benchtop Fluorometers.
RFU indicates the fluorescence intensity measured by the instrument in relative units. Essentially, it represents the amount of light the instrument detects, but it is not yet adjusted for calibration. Calibration is necessary to convert these raw measurements into meaningful data. For our instruments that can store calibration settings internally, the calibration process includes correcting for variations in excitation and emission spectra. This correction involves applying multiplicative factors specific to each calibration, which are adjusted based on the particular sample used for that calibration. These factors ensure that the instrument provides accurate and consistent fluorescence measurements.
As an example:
We frequently receive inquiries about why two AquaFluor instruments with Rhodamine channel optics, manufactured in different years, display different RFU values when measuring the same known concentration solution before calibration. The Raw Fluorescence Unit (RFU) value reflects how the instrument interprets the light into data, but it is not very useful for comparison without calibration. To get accurate and consistent measurements, it's important to calibrate both instruments with a known calibration solution. This ensures that the RFU values are standardized and comparable, rather than relying solely on uncalibrated RFU readings.
We also recommend that you should calibrate both instruments using the same calibration solution. Once calibrated, both instruments will provide consistent readings across an instrument model of the same type. This process helps ensure that our instruments give identical results and reduces variation in sample measurements. Calibrating two different model types of our instruments will not produce the same effect.