A novel wind speed and direction sensor designed for the atmosphere of Mars is described. It is based on an spherical shell divided into four triangular sectors according to the central projection of tetrahedron onto the surface of the unit sphere. Each sector is individually controlled to be heated above the ambient temperature independently of the wind velocity and incidence angle. A convection heat rate model of four hot spherical triangles under forced wind has been built with FEM thermal-fluidic simulations. The angular sensitivity of the tetrahedral sphere structure has been determined theoretically and compared with tessellation of the sphere by four biangles. A 9mm diameter prototype has been assembled using 3-D printing of the spherical shell housing in the interior commercial platinum resistors connected to an extension of a custom design printed board. Measurements in Martian-like atmosphere demonstrate sensor responsiveness to the flow in the velocity range 1m/s to 13m/s at 10mBar CO2 pressure. Numerical modelization of the sensor behavior allows to devise an inverse algorithm to retrieve the wind direction data from the raw measurements of the power delivered to each spherical sector. The functionality of the inverse algorithm is also demonstrated.

The objective of this paper is to introduce a modeling strategy to characterize the dynamics of the charge trapped in the dielectric of MOS capacitors, using Diffusive Representation. Experimental corroboration is presented with MOS capacitors made of Alumina in three different scenarios. First, the model predictions are compared with the trapped charge evolution due to arbitrary voltage excitations. Second, the predictions are compared with the measurements of a device in which a sigmadelta control of trapped charge is implemented. Finally, the time evolution when the device is simultaneously controlled and irradiated with X-rays is compared with the predictions. In all cases, a good matching between the models and the measurements is obtained.

This work describes a new circuit which applies a configurable voltage across an RTD while the current flowing through it is measured with a current mirror. The circuit also allows to work with voltages above the IC supply voltage to cope with the high power RTD dissipation normally required in thermal anemometers. The circuit is periodically calibrated to cancel the errors and amplifier offset and therefore improves measurement accuracy. Experimental measurements of the circuit fabricated using 0.35 µm AMS technology show the functionality and improved power efficiency.Introduction: Thermal anemometers are widely used to measure flow velocity by sensing the heat transfer between the fluid and a hot element [1][2][3]. Open and closed loop strategies have been extensively used [4][5][6][7] to measure the convection heat transfer. Several challenges have to be faced, the first is how to increase the power efficiency as in a conventional anemometer bridge [7] at most 50% of the power goes to heat the sensing resistor. Moreover, the bridge arrangement does not allow four-wire measurement of the resistor value increasing noise and the measurement is sensitive to the amplifier offset. Finally, the anemometer bridge structure does not allow an easy programable target of the operation temperature.In this work a measurement strategy based on controlling a loop to keep constant the voltage across the RTD and measuring the current I RT D with a current mirror in series is proposed. At any value of the flow speed, the power delivered to the RTD is the maximum availableThe resistor value at a given flow speed can be calculated accurately using a four-wire measurement (The power efficiency can be greatly increased as the voltage drop in the current mirror can be kept much lower than the constant voltage drop across the sensing resistor.The described circuit can be used with several control loop arrangements such as constant voltage (CVA) [4], thermal sigmadelta modulation (Σ∆) [5] or pulse width modulation (PWM) [6]. To implement Σ∆ or PWM modulation the voltage applied across the RTD is switched between two values (to deliver high or low power) depending on the value of the current at given time. This circuit allows the configuration of the loop to set different voltage values. Since the accuracy of current measurement can generally be affected by offset errors [8], the circuit includes calibration and offset cancelation.