He invented two alloys, constantan and manganin. Weston developed measurement instruments for electrical current—the modern foundation for the voltmeter, ammeter and wattmeter. In 1888, he formed the Weston Electrical Instrument Corporation which was known for its voltmeters, ammeters, wattmeters, ohmmeters, frequency meters, transformers, and transducers. Weston developed a method for producing a "true" permanent magnet. Weston conceived of and built a magnetic speedometer. Weston also developed the dashboard ammeter for Harley-Davidson motorcycles. 