We propose a time domain analog front-end for real time water quality monitoring which can simultaneously detect dissolved oxygen (DO) concentration and temperature and transmit on a single frequency band. The DO information changes the centre frequency of an oscillator and a delay line switches the oscillator ON/OFF, where ON/OFF time depends on the ambient temperature. A power amplifier (PA) sends that signal to an antenna can choose among three different power supplies to have variable output swing depending on the present operating voltametric range. Therefore, the PA output essentially combines and transmits three data simultaneously over a single channel of the 2.4GHz ISM band. The linear ranges of amperometric and temperature measurement circuits are ±200nA and 2oC-60oC (with 4 different sensitivities) having average R2 linearity of 0.99993 and 0.9997. Their respective noise levels are 40.4 pA and 0.33 ppm/ oC