Low-Cost Capacitive Humidity Sensor for Application Within Flexible RFID Labels Based on Microcontroller Systems

Pelegrí-Sebastiá, José; García‐Breijo, Eduardo; Ibáñez, Javier; Sogorb, T.; Laguarda-Miró, N.; Garrigues, Jose

doi:10.1109/tim.2011.2164860

Cited by 41 publications

(24 citation statements)

References 19 publications

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“…The direct interface circuits shown in Figure 6 have been applied mostly to measure capacitive relative humidity (RH) sensors [23,25,27], but also tilt sensors or accelerometers [24]. Table 9 summarizes the performance of such direct interface circuits in some of the previous applications.…”

Section: Applications and Resultsmentioning

confidence: 99%

“…From the author's point of view, future work on direct interface circuits could be focused on the following two directions: (a) Applications: Many measurement systems based on resistive and capacitive sensors, but especially those intended for low-cost low-power applications, could benefit from the advantages of direct interface circuits. In fact, recently, such circuits have been proposed to measure low-power magnetic sensors for vehicle detection [30], low-power gas sensors [19] and low-cost low-power RH sensors to be integrated into RFID labels [27]. (b) Measurement of other types of sensor: Most of the research work done so far on direct interface circuits has been focused on measuring resistive and capacitive sensors, but the direct measurement of other types of sensor is also of interest.…”

Section: Discussionmentioning

confidence: 99%

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The Art of Directly Interfacing Sensors to Microcontrollers

Reverter

2012

JLPEA

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This paper reviews the direct connection of sensors to microcontrollers without using any analogue circuit (such as an amplifier or analogue-to-digital converter) in the signal path, thus resulting in a low-cost, lower-power sensor electronic interface. It first discusses the operating principle and explains how resistive and capacitive sensors with different topologies (i.e., single, differential and bridge type) can be directly connected to a microcontroller to build the so-called direct interface circuit. It then shows some applications of the proposed circuits using commercial devices and discusses their performance. Finally, it deals with the power consumption and proposes some design guidelines to reduce the current consumption of such circuits in active mode.

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Section: Applications and Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

The Art of Directly Interfacing Sensors to Microcontrollers

Reverter

2012

JLPEA

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“…The existence of a tradeoff between the measurement uncertainty (u R m ) and the energy consumption (E Meas ) will be demonstrated for the circuit of Applying the law of uncertainty propagation [16], u R m can be obtained from Assuming (2) and (3) are used to deduce…”

Section: Design Constraintsmentioning

confidence: 99%

“…It is one of the main design bottlenecks for incoming new technologies such as powerless sensor nodes integrated in passive radio-frequency identifier systems [1], [2]. Although the main research efforts have focused on lowering the energy spent by the communication system [3], the measurement process can spend more energy whenever not all the measurement data are transmitted.…”

Section: Introductionmentioning

confidence: 99%

Low-Power Direct Resistive Sensor-to-Microcontroller Interfaces

López-Lapeña

Serrano-Finetti

Casas

2016

IEEE Trans. Instrum. Meas.

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Abstract-This paper analyzes the energy consumption of direct interface circuits where the data conversion of a resistive sensor is performed by a direct connection to a set of digital ports of a microcontroller (μC). The causes of energy consumption as well as their relation to the measurement specifications in terms of uncertainty are analyzed. This analysis yields a tradeoff between energy consumption and measurement uncertainty, which sets a design procedure focused on achieving the lowest energy consumption for a given uncertainty and a measuring range. Together with this analysis, a novel experimental setup is proposed that allows one to measure the μC's timer quantization uncertainty. An application example is shown where the design procedure is applied. The experimental results fairly fit the theoretical analysis, yielding only 5 μJ to achieve nine effective number of bits (ENOB) in a measuring range from 1 to 1.38 k . With the same ENOB, the energy is reduced to 1.9 μJ when the measurement limits are changed to 100 and 138 k .

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“…With the aim of reducing the cost and power consumption of sensor electronic interfaces, the concept of "direct interface circuit" has been widely proposed, analysed and tested for resistive [10][11][12] and capacitive [13][14][15] sensors. In these circuits, the sensor resistance (or capacitance) together with a capacitor (or resistor) form an RC circuit whose charging or discharging time is directly measured by a µC through an embedded digital timer and without using any intermediate active circuit (such as comparators, OpAmps, timers and/or ADC).…”

Section: Introductionmentioning

confidence: 99%

Direct inductive sensor-to-microcontroller interface circuit

Kokolanski

Barnils

Gasulla

et al. 2015

Sensors and Actuators A: Physical

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Abstract-This paper proposes and analyses a microcontroller-based interface circuit for inductive sensors with a variable self-inductance. Besides the microcontroller (µC) and the sensor, the circuit just requires an external resistor and a reference inductor so that two RL circuits are formed. The µC appropriately excites such RL circuits in order to measure the discharging time of the voltage across each inductor (i.e. sensing and reference) and then it uses such discharging times to estimate the sensor inductance. Experimental tests using different commercial µCs at different clock frequencies show the limitations (especially, due to parasitic resistances and quantisation) and the performance of the proposed circuit when measuring inductances in the millihenry range. A non-linearity error lower than 0.3% FullScale Span (FSS) and a resolution of 10 bits are achieved, which are remarkable values considering the simplicity of the circuit.

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Low-Cost Capacitive Humidity Sensor for Application Within Flexible RFID Labels Based on Microcontroller Systems

Cited by 41 publications

References 19 publications

The Art of Directly Interfacing Sensors to Microcontrollers

The Art of Directly Interfacing Sensors to Microcontrollers

Low-Power Direct Resistive Sensor-to-Microcontroller Interfaces

Direct inductive sensor-to-microcontroller interface circuit

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