Abstract
The front-end circuit of blood diagnostic machine consists of a light source, photodiode and transimpedance amplifier (TIA). Various researchers have used separate photodiode and the TIA circuit to measure absorbance for different wavelengths that made the circuit bulky and limited its application for measurement of specific parameters. At high gain of around 4000 plus normally any amplifier, including TIA becomes unstable. We are presenting here auto gain TIA that is stable and precise even at the gain of 4000. MSP432 32 BIT Arm Cortex 4 microcontroller with inbuilt precision analog to digital convertor is used for sensing, implementing auto gain selection logic and calculating the absorbance. With this circuit, we measured the absorbance up to 4.2 and satisfactory results with maximum error of 0.04 were achieved up to the range of 3.5 on the absorbance scale. Further, the performance of TIA is tested and found satisfactory for 300nm to 800nm wavelength range.
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More From: IOP Conference Series: Materials Science and Engineering
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