A portable analog lock-in amplifier for accurate phase measurement and application in high-precision optical oxygen concentration detection

Abstract

A portable analog lock-in amplifier capable of accurate phase detection is proposed in this paper. The proposed lock-in amplifier, which uses the dual-channel orthometric signals as the references to build the xy coordinate system, can detect the relative phase between the input and x-axis based on trigonometric function. The sensitivity of the phase measurement reaches 0.014 degree, and a detection precision of 0.1 degree is achieved. At the same time, the performance of the lock-in amplifier is verified in the high precision optical oxygen concentration detection. Experimental results reveal that the portable analog lock-in amplifier is accurate for phase detection applications. In the oxygen sensing experiments, 0.058% oxygen concentration resulted in 0.1 degree phase shift detected by the lock-in amplifier precisely. In addition, the lock-in amplifier is small and economical compared with the commercial lock-in equipments, so it can be easily integrated in many portable devices for industrial applications.

Keywords

Portable analog lock-in amplifier / phase shift measurement / high accuracy / optical oxygen detection

References

[1] Marcellis A. D., Ferri G., D'Amico A., Natale C. D.. A fully-analog lock-in amplifier with automatic phase alignment for accurate measurements of ppb gas concentrations. Sensors Journal IEEE, 2012, 12(5): 1377-1383.

[2] Graaf G., Wolffenbuttel R. F.. Lock-in amplifier techniques for low-frequency modulated sensor applications. Conference Record–IEEE Instrumentation and Measurement Technology Conference, 2012, 8443(8): 1745-1749.

[3] Aguirre J., García-Romeo D., Medrano N., Calvo B., Celma S.. Square-signal-based algorithm for analog lock-in amplifiers. IEEE Transaction on Industrial Electronics, 2014, 61(10): 5590-5598.

[4] Gabal M., Medrano N., Calvo B., Martínez P. A., Celma S., Valero M. R.. A complete low voltage analog lock-in amplifier to recover sensor signals buried in noise for embedded applications. Procedia Engineering, 2010, 5(41): 74-77.

[5] Amico A., Marcellis A., Carlo C. D., Natale C. D., Ferri G., Martinelli E., . Low-voltage low-power integrated analog lock-in amplifier for gas sensor applications. Sensors and Actuators B Chemical, 2010, 144(2): 400-406.

[6] Aguirre J., Medrano N., Calvo B., Celma S.. Lock-in amplifier for portable sensing systems. Electronics Letters, 2011, 47(21): 1172-1173.

[7] Walker W. D.. Sub-microdegree phase measurement technique using lock-in amplifiers. IEEE International Frequency Control Symposium, 2008 825-828.

[8] Azzolini C., Magnanini A., Tonelli M., Chiorboli G., Morandi C.. Integrated lock-in amplifier for contact-less interface to magnetically stimulated mechanical resonators. 3rd International Conference on Design and Technology of Integrated Systems in Nanoscale Era, 2008 1-6.

[9] A. D. Marcellis and G. Ferri, Detection of small and noisy signals in sensor interfacing: the analog lock-in amplifier. Netherlands: Springer, 2011: 181–204.

[10] H. M. Kalayeh, G. R. Paz-Pujalt, and J. P. Spoonhower, “System and method for remote quantitative detection of fluid leaks from a natural gas or oil pipeline,” US Patent 6822742, 2004.

[11] Quaranta M., Borisov S. M., Klimant I.. Indicators for optical oxygen sensors. Bioanalytical Reviews, 2012, 4(2–4): 115-157.

[12] McEvoy A. K., Mcdonagh C. M., Maccraith B. D.. Dissolved oxygen sensor based on fluorescence quenching of oxygen-sensitive ruthenium complexes immobilized in sol–gel-derived porous silica coatings. Analyst, 1996, 121(6): 785-788.

[13] Murtagh M. T., Ackley D. E., Shahriari M. R.. Development of a highly sensitive fiber optic O2 sensor based on a phase modulation technique. Electronics Letters, 1996, 32(5): 477-479.

[14] Mcdonagh C., Kolle C., Mcevoy A. K., Dowling D. L., Cafolla A. A., Cullen S. J., . Phase fluorometric dissolved oxygen sensor. Sensors and Actuators B Chemical, 2001, 74(1–3): 124-13.

[15] Limpouchová Z., Procházka K.. Theoretical principle of fluorescence spectroscopy, 2016, Netherlands: Springer