A Measuring System for Low Frequency Noise in Resistive Gas Sensors

In this paper, a versatile measurement system to characterize noise in resistive sensors is presented. To reliable measure sub-Hz physical variables like gas concentration, the noise processes that affect the sensor need to be understood, and thus is important to have reliable low frequency noise measurements. Low-level measurements are achieved by employing 23.8-bit-ENOB ADC and low noise analog signal conditioning. The circuit has two identical channels that allow the recording of a reference sample while the noise of a sensor is being measured. Each channel has four different biasing circuits to experiment with different circuit topologies and increase the versatility of the setup. The system was tested with a polypyrrole chemiresistive gas sensor and found to be capable of measuring the low-frequency noise, down to 1 mHz in all four configurations.