SIGNAL-ENHANCEMENT SYSTEM FOR PHOTODETECTOR OUTPUTS

摘要

A light scattering photometer signal-enhancement systems includes an adaptive sample and subtract circuit controlled by a computer or microcontroller (MCU). The MCU controls the gain of a programmable-gain amplifier (PGA) cascade that is used to amplify the raw photometer signal. In order to maintain the DC accuracy, the DC offset contained in the raw signal from the photometer is estimated by an algorithmic within the MCU and then subtracted from the raw signal before allowing it to be amplified by the PGA cascade. In addition to DC estimation and adaptive cancellation, the MCU applies a digital filtering scheme to compensate irrelevant frequency bands in the amplified signal and offers user determined averaging functions for additional signal conditioning. Moreover, hardware filters are used to prevent signal aliasing by the analog to digital converters (ADC) and a 60 Hz notch filter suppresses general electrical noise.