Giving Delta-Sigma Converters

Sensing small signals is a challenge in process control environments where the sensors used to capture tempera- ture, pressure, and other environmental information produce low level signals. These signals can easily be masked by the ambient noise in the physical vicinity of the measurement, placing tough requirements on the electronics in the remain- der of the signal path. If a high level of accuracy is required in these data acquisition systems, the effective signal full- scale range must be decreased making the signal-to-noise ratio (SNR) higher. Several techniques, in the digital domain as well as analog domain, can be used to improve the signal-to-noise ratio of the sensing system. An example of a circui  that can easily implement digital and analog techniques to  improve the signal to noise ratio is shown in Figure 1. In this circuit an instrumentation amplifier is used at the front end of the analog signal path. This analog gain stage directly changes the effective full scale range of the overall system. Following the instrumentation amplifier, a delta-sigma con- verter is utilized because of its internal analog gain and digital filtering capability. When the delta-sigma converter  is properly configure, analog gain and digital filtering are optimized to further improve the SNR. The finishing touches of the signal conditioning is performed by the µController,where software gain or bit shifting is used.