Neutralization of the ion beam produced by a FEEP thruster is in principle a task similar to the well-known problem of neutralizing a traditional ion rocket.On the other hand, the neutralization of a small, micronewton thrust level FEEP poses several practical problems. The neutralizer has to produce a very low electron current, that must couple with the very fast ions exhausted by the thruster. As the envisaged use of FEEP is based on its fine throttling capabilities, the neutralizer has to be proportionately able to follow the variations of the ion current, with the same rapidity. A first experimental assessment of the problem has been recently performed at Centrospazio. A series of test has been carried out on a 3 cm emitter, together with two neutralizers, namely a plasma bridge hollow cathode and a hot filament. The hollow cathode, developed by SEP, was fed by gaseous cæsium. A thoriated tungsten filament was also tested. The thruster and neutralizer operational parameters have been recorded, including the coupling potential between the neutralizer and the ion beam. In order to measure this potential, the thruster assembly was electrically isolated from the vacuum facility and kept floating during the tests. This paper presents the experimental setup and the test results. A critical analysis of the data gathered is provided, aimed at the identification of the optimal technology for a flight model.