Knowledge Bank

The chopped-beam, double-beam, and double-pass methods, and combinations and variations of these, have sparked the development of various spectrometric systems, and suggest other, yet untried, systems. The following systems are discussed qualitatively as to convenience and freedom of errors, and are compared quantitatively to the single-pass chopped-beam (first harmonic only) as to noise factor (n. f.): DC thermocouple (n.f., .45) Single-beam single-pass (n.f., 1.00) Double-beam single-pass (n.f., 1.00) Single-beam double-pass (n.f., 1.00) Halford-Savitzky twin-beam (n.f., 2.30) Hornig double-beam (n.f., 1.62) A modified Hornig double-beam (n.f., 1.09) The speaker’s twin-beam phase system, developed at the Eppley Laboratory (n.f., 2.37 and 2.85, the latter permitting double-pass operation). A twin-beam phase system with phase nulling (n.f., 1.12) A double-beam double-pass system proposed by Coates-Scott (n.f., 2.00) A modified Coates-Scott system (n.f., 1.62) A double-beam double-pass phase system (n.f., 2.11)