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    I came across this question in my textbook while revising.

    Q) Explain why the biosensor and colorimeter need to be calibrated?

    The answer on the mark scheme states.

    I really can't understand what this means, is someone able to make sense of this?

    The importance of calibration is to ensure that you do not end up having a systematic error - for example when a scale weighs wrong and indicates the mass of everything to be 2g higher than the actual mass.

    Calibrating a colorimeter with a blank cuvette shows us what 100% transmittance and 0% absorbance is. The following measurements of absorbance or transmittance of the samples in your experiment will be measured in relation to the initial absorbance or transmittance set by the blank cuvette when callibrating. Without calibration, a cuvette containing a purple solution could be declared as 100% transmittance by the colorimeter even though it is clearly not allowing all the light to pass straight through (which would truly be 100% transmittance)

    The answer given by the mark scheme refers to "electrical signal" because it is referring to the biosensor, whereas I have been referring to "transmittance" or "absorbance" given by the colorimeter.

    I hope this helps and good luck!
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