Various methods and devices are provided for removably coupling a sensor assembly to a catheter to measure conditions surrounding the catheter when the catheter is implanted in a patient. In one embodiment and a modular sensor assembly is provided and includes a housing having an antenna therein adapted to be removably coupled to at least a portion of a catheter. The housing can be a closed loop having an opening therethrough. One or more sensors can be coupled to the antenna for measuring conditions surrounding the catheter when the catheter is implanted in a patient. In one embodiment, the housing can be adapted to removably couple to a distal end of the catheter and the opening of the housing can be adapted to receive the catheter. The antenna can be a loop disposed within the housing.
