Abstract: A fuel economy indicator for vehicles having liquid fuel engines. The indicator comprises fuel flow and vehicle speed sensors, and means for using the information provided by such sensors to determine and display a performance ratio, consisting of the ratio of the instantaneous rate of fuel usage to the average rate of fuel usage.

Abstract: A method and apparatus for sampling a particle-bearing gas in which a vacuum is applied to the gas to generate a stream of gas, the flow of the stream is maintained constant, and particles are collected from the stream. A constant flow controller responsive to the static pressure of the gas in the stream provides a flow restriction which gradually decreases to compensate for a gradually increasing flow restriction caused by particles collecting on an initially particle-free collection filter located in the stream.

Abstract: An improved integrating nephelometer having superior sensitivity and long-term stability to previous designs includes a container defining a measurement chamber. A continuously energized light source, such as a tungsten filament incandescent bulb, illuminates the measurement chamber through an opal glass diffuser. The intensity of the light source is regulated in one embodiment by a simple optical-electric feedback system, and in another embodiment by a voltage regulated supply. A cone of observation of the chamber is defined by a plurality of spaced, apertured plates located in the chamber, at right angles to the light source. A measuring photomultiplier tube views the cone of observation and provides an output signal including components resulting from detected photoelectrons, noise, and thermally emitted "dark current" electrons. A photon-detecting apparatus removes the noise component and provides an output pulse for each photoelectron and "dark current" electron.