Abstract: An instrument has a rotatable part and a helical spring secured to the instrument casing at its outer end and to the rotatable part at its inner end. The spring characteristics are made to depart from linear, by changing the cross-sectional area of the spring progressively substantially from one end to the other of the spring. Preferably, the spring thickness is kept constant and its width varied, as by providing a tapered slot through the spring along its length. Provision is made for further selectively varying the spring characteristics, by rendering inactive selected lengths of the outer turns of the spring. In one embodiment (FIGS. 1 and 2) this is done by providing a split ring that encircles the spring and whose ends can be moved toward or away from each other to contact selected lengths of the outer turns of the spring. In other embodiments (FIGS. 3 and 4) a helical rib coaxial and coextensive with the spring is rotated relative to the spring to contact varying lengths of the inner (FIG.

Abstract: An instrument for continuously indicating the instantaneous rate of fuel consumption (e.g. in terms of liters per 100 kilometers) during operation of a motor vehicle comprises a stationary speed scale juxtaposed with a movable consumption scale, the two scales carrying relatively inverted logarithmic graduations and being swept by a common pointer driven through a gear train from a speedometer biased by a spring of logarithmic characteristic. The movable scale is magnetically entrained, via a friction coupling, by a flowmeter which is thermostatically controlled to take changes in fuel viscosity due to temperature variations into account; the friction coupling can be manually preadjusted in accordance with the specific weight of the fuel. The pointer and the movable scale are carried by two coaxial disks that coact through a differential coupling with a switch which energizes different signal lamps according to whether, at a given speed, the rate of fuel consumption is normal, subnormal or excessive.

Abstract: A flow-rate meter has a cylindrical housing in which a counterweighted blade is pivotable on a shaft about the axis of the housing which is subdivided by a radial partition, an inlet port and an outlet port opening axially into this housing on opposite sides of the blade. The blade is magnetically coupled with a logarithmic scale and is provided with a logarithmic spring against which the force of the water flowing past the blade works.