Dual data pulse width modulator for wireless Simultaneous Measurement of Redox Potential and Temperature using a Single RFID Chip

A dual data pulse width modulator has been proposed and demonstrated for simultaneous wireless measurement of two sensors. The measured modulation sensitivity of the two inputs were 84.69 and 85.16 μs/V, respectively. Here, redox potential and temperature were measured wirelessly using the proposed circuit. The measured redox potential showed fairly good linearity for a concentration ratio of hexacyanoferrate (III) to (II) ranging from 10^-2 to 10² and the slope was 58.0 mV/decade, almost the same as the theoretical value. Temperature change measurement shows a sensitivity of 9.501 μs/°C in the range of 25-40°C. The chip area and power consumption were 0.36 mm² and 650 μW, respectively, using 1.2-μm, 2-metal, 2-poly CMOS technology.