set pointer

11111.1111114111 Aneroid barometers invariably have two pointers: one that is operated by the mechanics, and one that is set manually. The manually set pointer is really nothing but a mechanical memory that enables variations in barometric pressure to be ascertained. The set pointer can, of course, be made electronic, for which a slide potentiometer is ideal. Such a pointer is not restricted to a barometer: it can also be used with a thermometer, a hygrometer, a battery that needs to be monitored; in short, with any sensor that delivers a slowly varying voltage. The circuit consists of an amplifier, IC1, and a display stage, IC2. The display consists of between 3 and 9 LEDs, the centre one of which, D5, is yellow and represents the point of origin. Potentiometer P1can be adjusted to make this LED light. When the input voltage rises slightly, D6 (the colour of which depends on the application) lights; when it drops, 0 4 (again, the colour depends on the application, but it should b...