sensors behave similarly and these calibration curves can be used with other type of sensors according to embodiments of the present invention sensor recalibrations will be performed not only based on independent characteristic values e g blood meter values but with use of the expected normalized calibration curves as will be described in greater detail below with respect to fig4 and 5 in fig2 the vertical axis designated as i g i g0 represents the ratio of real time glucose current to an imaginary glucose current in the absence of glucose i g represents a sensor current output modulated by real time glucose measurements i g0 represents a nominal value of the sensor output current when no glucose is present for measurement i g0 can be calculated using the following formula where r is a conversion factor that is based on blood meter values to calibrate the sensor and i o is oxygen electrode output current since the presence of glucose lowers the glucose current i g should never exceed i g0 therefore the highest point along y axis is 1 when i g i g0 the horizontal axis designated by c g c o represents the ratio of measured glucose concentration versus a nominal glucose concentration c g represents the glucose concentration c o may be calculated by multiplying a nominal sensor oxygen electrode output current i o by a constant in other words in equation 1 the value u201c k u201d is a constant based on the ratio of the oxygen concentration to the oxygen electrode current as described previously phase 1 of the sensor 39 s life may be viewed as a sensitivity period during the initial output of the sensor current with respect to.