A quantitative measurement system includes an external unit (101a) and an internal unit (102a) are provided for obtaining quantitative analyte measurements, such as within the body. In one example of an application of the system, the internal unit (102a) would be implanted either subcutaneously or otherwise within the body of a subject. The internal unit (102a) contains optoelectronics circuitry (102b), a component of which may be comprised of a fluorescence sensing device. The optoelectronics circuitry (102b) obtains quantitative measurement information and modifies a load (102c) as a function of the obtained information. The load (102c) in turn varies the amount of current through coil (102d), which is coupled to a coil (101f) of the external unit (101a). A demodulator (101b) detects the current variations induced in the external coil (101f) by the internal coil (102d) coupled thereto, and applies the detected signal to processing circuitry, such as a pulse counter (101c) and computer interface (101d), for processing the signal into computer-readable format for inputting to a computer (101e).