Marconi Instruments Limited was a British company, one of the Marconi group of companies, formerly part of GEC. In 1941, there was a buyout of Marconi-Ekco Instruments to form the company Marconi Instruments.
The company was based in St Albans,Colchester and Stevenage (where it eventually consolidated), all in southern England. Prior to the consolidation in Stevenage, its main site was at Longacres on the eastern outskirts of St Albans, where it was the largest employer. There were four other sites, one at Hedley Road, one on Hatfield Road, St Albans (Fleetville Works), one on the Donibristle Industrial Estate in Fife, Scotland and one at Luton Airport, Luton.
The company produced electronic test and measurement equipment and systems, including automatic test equipment. It was known for its extensive range of signal generators, from audio up to microwave frequencies. It also made oscilloscopes, voltmeters, spectrum analysers, frequency counters, function generators, component (LCR) bridges, impedance analysers, power supplies, distortion analysers, moisture meters and logic analysers. The company operated an approved calibration and metrology laboratory for the electronics industry.