A microcontroller-based lock-in amplifier for sub-milliohm resistance measurements

Bengtsson, Lars

doi:10.1063/1.4731683

Cited by 38 publications

(21 citation statements)

References 16 publications

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“…Another part of the signal processing circuit is a microcontroller-based digital lock-in amplifier (DLIA), as shown in Figure 2. Recently, several kinds of DLIAs have been studied, which, however, either use expensive and hard-to-develop integrated chips like Digital Signal Processor (DSP) [22] or Field-Programmable Gate Array (FPGA) [23], or employ the microcontrollers (MCU) [24] for only low frequency signal processing, with low precisions acquired, due to the limited computing power and lack of floating processing ability. As the rapid development of integrated circuits, a new MCU with a floating processing unit and digital signal processing instructions now is available for the DLIA as the sampling controller and computing core.…”

Section: Signal Processing Circuitsmentioning

confidence: 99%

Fully Integrated Photoacoustic NO2 Sensor for Sub-ppb Level Measurement

Dong

Zhu

et al. 2020

Sensors

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A fully integrated photoacoustic nitrogen dioxide (NO2) sensor is developed and demonstrated. In this sensor, an embedded photoacoustic cell was manufactured by using an up-to-date 3D printing technique. A blue laser diode was used as a light source for excitation of photoacoustic wave in the photoacoustic cell. The photoacoustic wave is detected by a sensitive microelectromechanical system (MEMS) microphone. Homemade circuits are integrated into the sensor for laser diode driving and signal processing. The sensor was calibrated by using a chemiluminescence NO–NO2–NOX gas analyzer. And the performance of this sensor was evaluated. The linear relationship between photoacoustic signals and NO2 concentrations was verified in a range of below 202 ppb. The limit of detection was determined to 0.86 ppb with an integration time of 1 s. The corresponding normalized noise equivalent absorption was 2.0 × 10−8 cm−1∙W∙Hz−1/2. The stability and the optimal integration time were evaluated with an Allan deviation analysis, from which a detection limit of 0.25 ppb at the optimal integration time of 240 s was obtained. The sensor was used to measure outdoor air and the results agree with that obtained from the NO–NO2–NOX gas analyzer. The low-cost and portable photoacoustic NO2 sensor has a potential application for atmospheric NO2 monitoring.

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Section: Signal Processing Circuitsmentioning

confidence: 99%

Fully Integrated Photoacoustic NO2 Sensor for Sub-ppb Level Measurement

Dong

Zhu

et al. 2020

Sensors

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“…O amplificador Lock-iné uma excelente ferramenta para medir sinais com pequenas amplitudes em sistemas imersos em ruído [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Neste caso, um Lock-in de 16 bits de resolução recebe um sinal do Chopper como referência e outro sinal do fotodector através do condicionador de sinais.…”

Section: Metodologiaunclassified

Aparato experimental para medidas de atividade óptica da sacarose usando um amplificador Lock-in

Fauth¹,

Batista²

2018

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Resumo: Este trabalho apresenta a montagem de um polarímetro digital para medidas de atividadeóptica em modo pulsado. Em termos de instrumentação científica, foi desenvolvido um circuito eletrônico para medir a intensidade luminosa usando um fotodetector em conjunto com outros componentesópticos e um amplificador Lock-in. Além disso, um porta amostra foi projetado utilizando uma lente de quartzo acoplada em uma tampa e conectada a um tubo de PVC. O desempenho do sistema de medidasé investigado considerando a resolução e o limite de detecção a partir da determinação da rotaçãoóptica específica da sacarose. Este trabalho foi desenvolvido tendo como base o paradigma open source hardware e, portanto, toda a documentação estará disponível para que possa ser utilizada e aprimorada pela comunidade científica.Palavras chave: AtividadeÓptica, Polarímetro, Lock-in, Open Source Hardware. Abstract:This work presents the assembly of a digital polarimeter for measurements of optical activity in pulsed mode.In terms of scientific instrumentation, an electronic circuit was developed to measure light intensity using a photodetector in conjunction with other optical components and a Lock-in amplifier. In addition, a sample port was designed using a quartz lens attached to a cap and connected to a PVC pipe. The performance of the measurement system is investigated considering the resolution and the limit of detection from the determination of the specific optical rotation of sucrose. This work was developed based on the open source hardware paradigm and, therefore, all the documentation will be available so that it can be used and improved by the scientific community.

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“…The LIA can be of analog or digital architecture, or both. The digital LIA has gained popularity as it is suitable for multi-frequency operation (Sun et al 2007;Sonnaillon and Bonetto 2005;Yang et al 2007;Yang et al 2009;Bo and Li 2015;Bengtsson 2012), hence commercial lock-in-amplifiers often use a digital architecture (Instruments 2017;FEMTO 2017). However to develop a portable hand-held LIA, where single frequency excitation is sufficient, the use of a costly and bulky digital architecture is excessive.…”

Section: Introductionmentioning

confidence: 99%

A portable battery powered microfluidic impedance cytometer with smartphone readout: towards personal health monitoring

Talukder

Furniturewalla

et al. 2017

Biomed Microdevices

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We present a portable system for personalized blood cell counting consisting of a microfluidic impedance cytometer and portable analog readout electronics, feeding into an analog-to-digital converter (ADC), and being transmitted via Bluetooth to a user-accessible mobile application. We fabricated a microfluidic impedance cytometer with a novel portable analog readout. The novel design of the analog readout, which consists of a lock-in-amplifier followed by a high-pass filter stage for subtraction of drift and DC offset, and a post-subtraction high gain stage, enables detection of particles and cells as small as 1 μm in diameter, despite using a low-end 8-bit ADC. The lock-in-amplifier and the ADC were set up to receive and transmit data from a Bluetooth module. In order to initiate the system, as well as to transmit all of the data, a user friendly mobile application was developed, and a proof-of-concept trial was run on a blood sample. Applications such as personalized health monitoring require robust device operation and resilience to clogging. It is desirable to avoid using channels comparable in size to the particles being detected thus requiring high levels of sensitivity. Despite using low-end off-the-shelf hardware, our sensing platform was capable of detecting changes in impedance as small as 0.032%, allowing detection of 3 μm diameter particles in a 300 μm wide channel. The sensitivity of our system is comparable to that of a high-end bench-top impedance spectrometer when tested using the same sensors. The novel analog design allowed for an instrument with a footprint of less than 80 cm. The aim of this work is to demonstrate the potential of using microfluidic impedance spectroscopy for low cost health monitoring. We demonstrated the utility of the platform technology towards cell counting, however, our platform is broadly applicable to assaying wide panels of biomarkers including proteins, nucleic acids, and various cell types.

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A microcontroller-based lock-in amplifier for sub-milliohm resistance measurements

Cited by 38 publications

References 16 publications

Fully Integrated Photoacoustic NO2 Sensor for Sub-ppb Level Measurement

Fully Integrated Photoacoustic NO2 Sensor for Sub-ppb Level Measurement

Aparato experimental para medidas de atividade óptica da sacarose usando um amplificador Lock-in

A portable battery powered microfluidic impedance cytometer with smartphone readout: towards personal health monitoring

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