A very small Fermi‐type neutron chopper fashioned by cutting slots in a boron nitride cylinder was developed for use with a source of thermal and cold (subthermal velocity) neutrons. The original goal was to characterize spectra emerging from glass capillary fibers of less than 1 mm diameter, but other applications became apparent. For approximately 1 m flight paths, conventional nuclear electronics had to be adapted to the millisecond flight times. Both time‐to‐amplitude converter and multiscaling time‐data storage methods were used. Data corrections for the particular geometry are reviewed and applied to the present geometry. Among examples of its potential use, the spectrum of a newly installed cold source was measured. ©1996 American Institute of Physics.