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A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

He D, Morgan SP, Trachanis D, van Hese J, Drogoudis D, Fummi F, Stefanni F, Guarnieri V, Hayes-Gill BR - Sensors (Basel) (2015)

Bottom Line: The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations.With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise.The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

View Article: PubMed Central - PubMed

Affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.

ABSTRACT
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

No MeSH data available.


CMOS Sensor chip and LED illumination PCBs.
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sensors-15-17076-f002: CMOS Sensor chip and LED illumination PCBs.

Mentions: Figure 2 shows the prototype including a test board with the CMOS sensor chip and an LED board. The light source consists of four λ = 660 nm (ROHM—SML-310LTT86N) and four λ = 940 nm (KINGBRIGHT—KP-2012F3C) LEDs, providing even illumination to the tissue. There are four holes at the corners of the LED board and four corresponding pins on the CMOS sensor board for fixation. In reflection configuration, the LED board is placed at the top of the CMOS sensor board with LEDs facing upward, the light backscattered by the tissue passes through the central hole (4 mm × 4 mm) and illuminates the photodiode on the CMOS sensor. The separation of the LED and the CMOS sensor is 5 mm. The system can also work in transmission mode by flipping the LED board so that it is situated on top of the finger.


A Single-Chip CMOS Pulse Oximeter with On-Chip Lock-In Detection.

He D, Morgan SP, Trachanis D, van Hese J, Drogoudis D, Fummi F, Stefanni F, Guarnieri V, Hayes-Gill BR - Sensors (Basel) (2015)

CMOS Sensor chip and LED illumination PCBs.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4541923&req=5

sensors-15-17076-f002: CMOS Sensor chip and LED illumination PCBs.
Mentions: Figure 2 shows the prototype including a test board with the CMOS sensor chip and an LED board. The light source consists of four λ = 660 nm (ROHM—SML-310LTT86N) and four λ = 940 nm (KINGBRIGHT—KP-2012F3C) LEDs, providing even illumination to the tissue. There are four holes at the corners of the LED board and four corresponding pins on the CMOS sensor board for fixation. In reflection configuration, the LED board is placed at the top of the CMOS sensor board with LEDs facing upward, the light backscattered by the tissue passes through the central hole (4 mm × 4 mm) and illuminates the photodiode on the CMOS sensor. The separation of the LED and the CMOS sensor is 5 mm. The system can also work in transmission mode by flipping the LED board so that it is situated on top of the finger.

Bottom Line: The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations.With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise.The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

View Article: PubMed Central - PubMed

Affiliation: Electrical System and Optics Research Division, Faculty of Engineering, University of Nottingham, University Park, Nottingham NG7 2RD, UK. diwei.he@nottingham.ac.uk.

ABSTRACT
Pulse oximetry is a noninvasive and continuous method for monitoring the blood oxygen saturation level. This paper presents the design and testing of a single-chip pulse oximeter fabricated in a 0.35 µm CMOS process. The chip includes photodiode, transimpedance amplifier, analogue band-pass filters, analogue-to-digital converters, digital signal processor and LED timing control. The experimentally measured AC and DC characteristics of individual circuits including the DC output voltage of the transimpedance amplifier, transimpedance gain of the transimpedance amplifier, and the central frequency and bandwidth of the analogue band-pass filters, show a good match (within 1%) with the circuit simulations. With modulated light source and integrated lock-in detection the sensor effectively suppresses the interference from ambient light and 1/f noise. In a breath hold and release experiment the single chip sensor demonstrates consistent and comparable performance to commercial pulse oximetry devices with a mean of 1.2% difference. The single-chip sensor enables a compact and robust design solution that offers a route towards wearable devices for health monitoring.

No MeSH data available.