Bandgap Temperature Sensors Research Articles

Brief communication: Comparison of the performance of thermistors and digital temperature sensors in a mountain permafrost borehole

Abstract. Monitoring mountain-permafrost temperatures in boreholes is challenging regarding the resilience and long-term temperature stability of the sensor systems. Whilst resistance thermistors boast a high accuracy, they are prone to drift when exposed to moisture, pressure or cable strain. Supplementing or replacing them with digital bandgap temperature sensors requires careful analysis of the sensor performance. We carry out a first comparison of two temperature sensor systems under field conditions in mountain permafrost at 15 identical depths in 1 borehole. Temperature values, sensing delays and noise levels are compared and discussed.

A Stacked Multi-Sensor Platform for Real-Time MRI Guided Interventions

We present a stacked temperature, pressure, and localization platform, targeted for minimally invasive surgical and diagnostic applications under Magnetic Resonance Imaging. The platform comprises a micro-fabricated three-layer (Titanium-Parylene-Titanium) membrane pressure sensor, a Gallium Arsenide band-gap temperature sensor, and a magnetic material on double prism retro-reflector that benefits from Magneto-Optic Kerr effect as a magnetic field sensor, to provide localization feedback under Magnetic Resonance Imaging. All sensors can be addressed with a single fiber optic cable, where the collected light is directed to a spectrometer and a polarimeter. For the three-layer microfabricated membrane sensor, an analytical formulation is derived, linking the pressure to optical intensity. Moreover, finite-element simulation results are provided, verifying analytical findings. Wavelength division multiplexing is exploited to address the sensors simultaneously. We measured sensitivities of 0.025 millidegree/Gauss rotation of polarization, 1.5 nm/mmHg displacement (in agreement with simulation results and analytical findings), 0.36 nm/°C bandgap wavelength shift for magnetic field, pressure, and temperature sensors; respectively. With further development, the proposed device can be adapted to a clinical setting for use in Magnetic Resonance assisted surgical procedures.

High-temperature characterisation and analysis of leakage-current-compensated, low-power bandgap temperature\xa0sensors

This paper analyses leakage current compensation techniques for low-power, bandgap temperature sensors. Experiments are conducted for circuits that compensate for collector-substrate, collector-base, body-drain and source-body leakage currents in a Brokaw bandgap sensor. The sensors are characterised and their failure modes are analysed at temperatures from 60 to 230^{,circ }hbox {C}. It is found that the most appropriate compensation circuit depends on the accuracy requirements of the application and on whether a stable reference voltage is required by other parts of the circuit. Experiments show that the power consumption is dominated by leakage current at high temperatures. One type of sensor was seen to consume 260 nW at 60 ^{,circ }hbox {C}, 2.1, upmu hbox {W} at 200^{,circ }hbox {C} and 14, upmu hbox {W} at 230^{,circ }hbox {C}. This work is motivated by the need to accurately monitor the temperature of power semiconductors in order to predict emerging faults in power semiconductor modules, a task for which cheap, single-chip, low-power, high-temperature, wireless bandgap temperature sensors are appropriate.

Superior Temperature-Sensing Performance in Cladding-Modulated Si Waveguide Gratings

This paper presents a silicon photonic temperature sensor based on a complementary metal-oxide-semiconductor (CMOS) compatible cladding-modulated (CladMod) grating design on the silicon-on-insulator platform. The resulting device achieves narrow-band reflection (Δλ = 0.63 nm), a high extinction ratio (21 dB), high temperature sensitivity (83.4 pm/°C), and a wide temperature-sensing range. More importantly, this grating design allows stable reflection bandwidth $\rm{(\Delta \lambda / \Delta W}_{\rm{g}}\,\rm{ = 0.013)}$ , Bragg wavelength $\rm{(\lambda }_{\rm{B }}\rm{/ \Delta W}_{\rm{g}}\,\rm{ = 0.002)}$ , and temperature sensitivity $\rm{(\delta \lambda / \delta T/ \Delta W}_{\rm{g}}\,\rm{ = - 1.3\times 10}^{- 5}\rm{ K}^{- 1}\rm{)}$ against variations in grating width. This level of temperature-sensing performance is difficult to achieve using a strip/slab-type grating or microring resonator. The CladMod gratings were further implemented on a polysilicon gate in a standard bulk CMOS process, thereby enabling integration with other microelectronic devices to serve as an on-chip distributed temperature-sensing element This approach shows considerable promise for applications such as future photonic-electronic integrated circuits requiring in situ temperature monitoring for wavelength stabilization, or high-temperature microelectronics where silicon bandgap temperature sensors are unable to operate properly

Integrated Multifunctional Environmental Sensors

We present the design, microfabrication, and characterization of ten sensors on one silicon die. We demonstrate simultaneous monitoring of multiple environmental parameters, including temperature, humidity, light intensity, pressure, wind speed, wind direction, magnetic field, and acceleration in three axes. Through an integrated design and fabrication process, these ten functions require only six photolithography mask steps. Temperature is measured redundantly using aluminum and doped silicon resistance thermal detectors and a bandgap temperature sensor. Humidity is transduced by the dielectric change of a polymer due to water absorption. Light intensity is measured with a p-n junction photodiode and doped silicon photoresistor. Pressure is transduced using piezoresistor strain gauges on a sealed membrane. Wind speed and direction are measured with two perpendicular hot wire anemometers. Magnetic field strength is measured with a doped Hall effect sensor. Acceleration in three axes is measured using electrostatic comb finger accelerometers, and an additional <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> -axis accelerometer uses piezoresistor strain gauges. We measured the cross-sensitivity of each function to all other environmental parameters and can use the chip's multifunctional capabilities to compensate for these effects. Sensor integration can enable significant cost, size, and power savings over ten individual devices and facilitate deployment in novel applications.

A Thermal-Diffusivity-Based Frequency Reference in Standard CMOS With an Absolute Inaccuracy of $\pm $0.1% From $-$55 $^{\circ}$C to 125 $^{\circ}$C

An on-chip frequency reference exploiting the well-defined thermal-diffusivity (TD) of IC-grade silicon has been realized in a standard 0.7 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\mu{\hbox{m}}$</tex></formula> CMOS process. A frequency-locked loop (FLL) locks the frequency of a digitally controlled oscillator (DCO) to the process-insensitive phase shift of an electrothermal filter (ETF). The ETF's phase shift is determined by its geometry and by the thermal diffusivity of bulk silicon ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$D$</tex> </formula> ). The temperature dependence of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$D$</tex></formula> is compensated for with the help of die-temperature information obtained by an on-chip band-gap temperature sensor. The resulting TD frequency reference has a nominal output frequency of 1.6 MHz and dissipates 7.8 mW from a 5 V supply. Measurements on 16 devices show that it has an absolute inaccuracy of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\pm $</tex></formula> 0.1% ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\sigma= \pm $</tex></formula> 0.05%) over the military temperature range ( <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$-$</tex></formula> 55 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{\circ}{\hbox{C}}$</tex></formula> to 125 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{\circ}{\hbox{C}}$</tex></formula> ), with a worst case temperature coefficient of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\pm \hbox{11.2~ppm}/^{\circ}{\hbox{C}}$</tex></formula> .