Design of integrated thermal flow sensors using thermal sigma—delta modulation

Verhoeven, H.J.; Huijsing, Johan H.

doi:10.1016/0924-4247(96)80149-x

Cited by 21 publications

(12 citation statements)

References 5 publications

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“…A schematic of the general topology for this circuit can be found in figure 9 (for δ=0) [4,9]. A pulsed power source is switched ON and OFF and the feedback loop keeps the integrator output close to the voltage offset (V off ) set at the input of the comparator.…”

Section: Thermal σ−∆ Modulator Dynamic Range Enhancementmentioning

confidence: 99%

“…The representation of the transfer function of the thermal filter (h(t)) as a function of a time constant density is [12]: (4) where f 0 is the clock frequency of the modulator. Assuming the finiteness of the above integrals, which is expected for most practical thermal circuits as they always act as strong low-pass filters (first time constant greater than 0), Equations in (3) and (4) show that for every value of λ 1 it is possible to work at a sufficiently high frequency such that the AC component at the output of the thermal integrator is smaller than any desired small value. In fact it is advisable to have a small AC component because if not, a fractal response is expected [9] and then, for some given voltage offsets, small variations of flow might not be detected at the output of the modulator.…”

Section: Thermal σ−∆ Modulator Dynamic Range Enhancementmentioning

confidence: 99%

“…Silicon devices have been developed [1][2][3][4] in which a micromachined channel is built and where thermal detectors are integrated on top of bridges across the duct. This solution achieves short response times but is restricted to very small air ducts and subject to problems of dust deposition and duct occlusion.…”

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confidence: 99%

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Low-cost thermal Σ-Δ air flow sensor

et al. 2002

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This paper describes the design and optimization of a hot-wire air flowmeter. A low cost design of the packaging allows good thermal contact with the airflow as well as good thermal isolation between the hot and cold points. It is a compact solution which allows easy PCB mounting and adaptation to standard size small air pipes. The design has been optimized for low-cost applications. The sensor is read out by a thermal sigma-delta modulator. The dynamic range of this modulator has been extended by adding a constant power offset to its output. The fractal nature of the modulator response at low clock frequencies is also experimentally shown.

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Section: Thermal σ−∆ Modulator Dynamic Range Enhancementmentioning

confidence: 99%

Section: Thermal σ−∆ Modulator Dynamic Range Enhancementmentioning

confidence: 99%

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Low-cost thermal Σ-Δ air flow sensor

et al. 2002

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“…Finally, for even more efficiency, a switching circuit may be used, possibly even combining switching with A/D conversion into thermal delta-sigma modulation [17] using a specialised circuit. However, several aspects must be borne in mind:…”

Section: Figurementioning

confidence: 99%

Integrated SMD pressure/flow/temperature multisensor for compressed air in LTCC technology: Thermal flow and temperature sensing

Maeder

Fournier

Coma

et al. 2011

Microelectronics Reliability

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“…One approach is to replace the loop filter by the sensor element because many active sensors have a first-or second-order lowpass transfer function. This technique was first employed in capacitive accelerometer designs with force feedback [16,22] and later adapted for thermal flow sensors [24] and microfluxgate sensors [25]. In the case of the capacitive sensor, no filtering function or feedback mechanism is available.…”

Section: Single-bit Rd-modulation Techniques For Sensor Interfacesmentioning

confidence: 99%

CMOS Single‐chip Gas Detection Systems: Part II

2003

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Sensor arrays based on industrial CMOS-technology combined with post-CMOS micromachining (CMOS MEMS) are a promising approach to low-cost sensors. In the first part of this article [1], the state of research on CMOS-based gas sensor systems was reviewed, and a platform technology for monolithic integration of three different transducers on a single chip was described. In this second part, the transduction principles of three polymer-based gas sensors are detailed and the read-out circuitry is portrayed. The first transducer is a micromachined resonant cantilever. The absorption of analyte in the chemically sensitive polymer causes shifts in resonance frequency as a consequence of changes in the oscillating mass. The cantilever acts as the frequency-determining element in an oscillator circuit, and the resulting frequency change is read out by an on-chip counter. The second transducer is a planar capacitor with polymer-coated interdigitated electrodes. This transducer monitors changes in the dielectric constant upon absorption of the analyte into the polymer matrix. The sensor response is read out as a differential signal between the coated sensing capacitor and a passivated reference capacitor, both of which are incorporated into the input stage of a switched capacitor second-order RD-modulator. The third transducer is a thermoelectric calorimeter, which detects enthalpy changes upon ab-/desorption of analyte molecules into a polymer film located on a thermally insulated membrane. The enthalpy changes in the polymer film cause transient temperature variations, which are detected via polysilicon/aluminum thermocouples (Seebeck effect). The small signals in the lVrange are first amplified with a low-noise chopper amplifier, then converted to a digital signal using a RD-A/D-converter and finally decimated and filtered with a digital decimation filter.

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Design of integrated thermal flow sensors using thermal sigma—delta modulation

Cited by 21 publications

References 5 publications

Low-cost thermal Σ-Δ air flow sensor

Low-cost thermal Σ-Δ air flow sensor

Integrated SMD pressure/flow/temperature multisensor for compressed air in LTCC technology: Thermal flow and temperature sensing

CMOS Single‐chip Gas Detection Systems: Part II

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