Abstract: An apparatus such as a domestic oven incorporates an induction motor which drives a fan. The temperature of the circulating gas and the slip of the rotor, coupled to the fan, are used to determine the humidity of gas within the oven. The temperature of the stator coil is also taken into account. The fan is driven with relatively high torque to maximize the signal to noise ratio. The fan may be provided as the main fan or as a secondary fan dedicated to humidity measurement. In either case the fan has a long operational lifetime.

Abstract: An apparatus such as a domestic oven incorporates an induction motor which drives a fan. The temperature of the circulating gas and the slip of the rotor, coupled to the fan, are used to determine the humidity of gas within the oven. The temperature of the stator coil is also taken into account. The fan is driven with relatively high torque to maximize the signal to noise ratio. The fan may be provided as the main fan or as a secondary fan dedicated to humidity measurement. In either case the fan has a long operational lifetime.

Abstract: A method of obtaining the concentration of one component in a fluid mixture of a plurality of components, comprising leading to one side of a sensing element from a source of said mixture a sample of said mixture, leading to another side of said sensing element from said source another sample of said mixture after having substantially removed said one component therefrom, thereby to cause a monitoring device to which said sensing element is connected to signal the ratio between the concentrations of the one component in the samples at the respective sides of the sensing element.

Abstract: A self-cleaning photovoltaic module which when combined with other identical modules forms a large solar panel which is protected from the vice of dust deposition. The module, which has all the properties of a solar panel in itself, has a dividing fin and a circular vent capable of flushing out the water along with the dust deposited on the module. The fins, which form a dam like structure, along with the aid of gravity guide the condensed atmospheric moisture along with the dust to the circular vents present on the corners of the photovoltaic module. The invention overcomes the difficulty of effectively self-cleaning a solar panel without much costs being involved.