Please cite this article in press as: V. Stornelli, et al., The assessment of wind conditions by means of hot wire sensors and a modifed Wheatstone bridge architecture, Sens. Actuators A: Phys. (2017), http://dx.doi.org/10.1016/j.sna.2017.05.005 ARTICLE IN PRESS G Model SNA-10114; No. of Pages 10 Sensors and Actuators A xxx (2017) xxx–xxx Contents lists available at ScienceDirect Sensors and Actuators A: Physical journal homepage: www.elsevier.com/locate/sna The assessment of wind conditions by means of hot wire sensors and a modifed Wheatstone bridge architecture V. Stornelli ∗ , G. Ferri, A. Leoni, L. Pantoli Department of Industrial and Information Engineering and Economics, University of L’Aquila, L’Aquila, Italy a r t i c l e i n f o Article history: Received 15 January 2017 Received in revised form 7 April 2017 Accepted 2 May 2017 Available online xxx Keywords: Hot wire anemometer Sensors Sensors interface Wheatstone bridge a b s t r a c t In this paper we present a novel complete anemometric electronic system based on an array of hot wire sensors, provided by Telecontrolli SME, and a suitable heater feedback that achieves, thanks to a dedicated algorithm, a CMOS integrable portable solution showing a robust design, without moving parts and small dimensions. The sensor interface is implemented by means of a modified Wheatstone bridge architecture with autobalancing capability. Comparisons with a commercial cup anemometer have shown that the proposed architecture, with reduced space occupancy and low power consumption, is suitable to operate in a natural environment in the −20 to +55 ◦ C temperature range providing wind speed and direction measurement. Concerning the wind speed, a 0.6 m/s sensitivity has been achieved. The integrated CMOS design of the final system is also presented and discussed in the paper. © 2017 Elsevier B.V. All rights reserved. 1. Introduction In the last few decades, wind related industries have invested a huge amount of money and resources to improve their products and systems. Their major goal has been the optimization of costs, operations, production, quality and time, that have been obtained through different improvement methods, tools and wind monitor- ing techniques [1–10]. These monitoring systems are necessary in different situations: from itinerant activities like sports (e.g. sail and ski) to bridges or urban buildings monitoring. Currently, different types of wind meters exist. A well-known solution is certainly the electrome- chanical or cup sensor, typically used in fixed stations [11–13]. Alternatives are usually based either on the pressure measurement or on the heat exchange with the air flow [3–6]. Such solutions are preferable for portable applications and installations in severe conditions. Thermal anemometry is the most common method used to mea- sure instantaneous fluid velocity. The technique depends on the convective heat loss to the surrounding fluid from an electrically heated sensing element or probe. The hot wire anemometer con- sists of a sensor, a small electrically heated wire exposed to the fluid flow and an electronic equipment, which performs the trans- formation of the sensor output into a useful electric signal. A hot ∗ Corresponding author. E-mail address: vincenzo.stornelli@univaq.it (V. Stornelli). wire anemometer is basically a thermal transducer: an electrical current crosses a fine metallic filament, which is exposed against the movement of a fluid. The heat generated by the flux of the elec- tric current in the filament is transferred to the fluid, so the thermal balance varies, modifying the electrical resistance. This variation can be quantified and monitored using suitable electronic circuits able to extrapolate the speed of the fluid. Basically there are two modes of operation for the hot wire anemometers: Constant Current Anemometer (CCA) and Constant Temperature Anemometer (CTA) [14–20]. For both the cases the electronic circuitry is a part of the anemometric system and has a direct influence on the probe characteristics. The basic principle of the system operation is the heat transfer from the heated wire to the cold surrounding fluid. The here proposed CTA anemometer [21,22] is based on a hybrid flow sensor, the FLW1 provided by Telecontrolli, which embeds a thermal resistor (heater) and a thermistor showing a negative thermal coefficient (NTC) on a ceramic substrate. The full system, comprehensive of an autobalancing modified Wheatstone bridge and a suitable heater feedback, is also easily integrable on a CMOS technology and achieves, thanks to a dedicated algorithm, a novel portable solution with a robust design, without moving parts and small dimensions. Comparisons with a commercial cup anemome- ter have shown that the proposed architecture, with reduced space occupancy and low power consumption, is suitable to operate, being all components correctly operating in −20 to +55 ◦ C tem- perature range, providing wind speed with a sensitivity of 0.6 m/s. http://dx.doi.org/10.1016/j.sna.2017.05.005 0924-4247/© 2017 Elsevier B.V. All rights reserved.