Low-power A.C. generators of square-wave or sinusoidal signals can be used in combination with impedimetric sensors to detect stimuli on the basis of the voltage drop taking place at the sensor electrodes. When a.c. generators with a power of only a few µ-Watts are used, this approach becomes extremely sensitive. A very low-power generator is the LCD back panel driving signal, which has a flipping polarity with a voltage of 3-5Vpp, depending on the generator model. This type of square-wave generator is contained in many low-cost handheld digital multimeters, and it is used as signal tracer to test, for example, low-frequency amplifiers. As an example, this method has been used to acquire a human breath rate pattern, by using a zeolite-based water sensor. If the generator I-V characteristics has been measured, the achieved breath pattern can be converted from a voltage drop vs. time graph to an impedance or current intensity vs. time graph.
A. Aliverti, “Wearable technology: role in respiratory health and disease”, Breathe, vol. 13(2), pp. e27-236, 2017.
B.W. An, J.H. Shin, S.Y. Kim, S. Ji, J. Park, Y. Lee, J. Jang, Y.-G. Park, E. Cho, S. Jo, and J.-U. Park, “Smart sensor systems for wearable electronic devices”, Polymers, vol. 9(8), pp. 303-343, 2017.
M. Stoppa, and A. Chiolerio, “Wearable electronics and smart textiles: a critical review”, Sensors, vol.14(7), pp. 11957-11992, 2014.
H.E. van den Brom, E. Houtzager, S. Verhoeckx, Q.E.V.N. Martina, and G. Rietveld, “Influence of sampling voltmeter parameters on RMS measurements of Josephson stepwise-approximated sine waves”, IEEE Transactions on Instrumentation and Measurement, vol. 58(10), pp.3806-3812, 2009.
I.N. Zhelbakov, “Low-frequency accuracy of rms voltmeters”, Measurement Techniques, vol. 40(2), pp. 30-33, 1997.
Z. Chen, and C. Lu, “Humidity sensors: a review of materials and mechanisms”, Sensor Letters, vol. 3(4), pp. 274-295, 2005.
J. Heikenfeld, A. Jajack, J. Rogers, P. Gutruf, L. Tian, T. Pan, R. Li, M. Khine, J. Kim, J. Wang, and J. Kim, “Wearable sensors: modalities, challenges, and prospects”, Lab on Chip, vol. 18(2), pp. 217-248, 2018.
G. Carotenuto, “Isothermal kinetic investigation of the water-cations interaction in natural clinoptilolite”, European Journal of Engineering Research and Science vol. 4(5), pp. 119-125, 2019.
This work is licensed under a Creative Commons Attribution 4.0 International License.
The names and email addresses entered in this journal site will be used exclusively for the stated purposes of this journal and will not be made available for any other purpose or to any other party.
Submission of the manuscript represents that the manuscript has not been published previously and is not considered for publication elsewhere.