Abstract: The chemical and/or physico-chemical determination of the ageing of a motor oil is very expensive and requires measuring methods which cannot be carried out on board a motor vehicle. The determination of only one oil condition parameter, for example the viscosity, only enables conditional statements to be made with respect to oil quality since conflicting effects may exist to varying degrees in this case. According to the invention, oil quality can be determined by a quartz base coated with a sensitive layer. The sensitive layer has a surface or volume which is adapted to an oil component and is suitable for the repeated incorporation and release of the oil component according to the concentration thereof. When the oil component is present, it is incorporated in the sensitive layer causing the resonant frequency of the layer to decrease via a mass effect or causing an effective increase of the component thickness or mass.

Abstract: The multi-roll calender for producing a sheet of elastomeric material comprises a calender frame and a series of rolls mounted in the calender frame. The rolls including an intake roll and a series of vertically superimposed rolls, with all adjacent rolls being variably spaced so as to provide variable roll gaps between each adjacent pair of rolls. Means are associated with the rolls for sensing the pressure of the material being calendered in each roll gap and means are provided on opposite ends of certain of the rolls responsive to the sensing means for adjusting the width of each roll gap formed by adjacent rolls to cause the difference between the pressures in said gaps to be as small as is practicable. Means are provided for maintaining the adjusted pressures substantially constant.

Abstract: A method of controlling a multi-roll calender producing a sheet of synthetic plastics, rubber or other elastomeric material comprising sensing the pressure of material being calendered in roll gaps of the calender, which roll gaps follow one after another in the direction of movement of the sheet; adjusting the width of the two gaps formed with mating rolls on opposite sides of at least some of the rolls to cause the difference between the pressures in the two gaps to be as small as is practicable; and maintaining such pressures substantially constant.