Description and accuracy tests of an improved lambdameter J. Cachenaut, C. Man, P. Cerez, A. Brillet, F. Stoeckel, A. Jourdan et F. Hartmann Rev. Phys. Appl. (Paris), 14 6 (1979) 685-688 DOI: 10.1051/rphysap:01979001406068500