Low Noise, Single-Supply, Toxic Gas Detector, Using an Electrochemical Sensor with Programmable Gain TIA for Rapid Prototyping

Application Circuit for the ADA4528-2 is a single-supply, low noise, portable gas detector, using an electrochemical sensor. The Alphasense CO-AX carbon monoxide sensor is used in this example. Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of many toxic gases. Most sensors are gas specific and have usable resolutions under one part per million (ppm) of gas concentration. The ADA4528-2, dual auto zero amplifier, which has a maximum offset voltage of 2.5 uV at room temperature and an industry leading 5.6 uV/Hz of voltage noise density. For applications where measuring fractions of ppm gas concentration is important, using the ADA4528-2 and the ADR3412 makes the circuit performance suitable for interfacing with a 16-bit ADC, such as the AD7790