Method for determining a pulse duration T₉₀ of a 90° pulse in a nuclear magnetic measuring method and respective nuclear magnetic flowmeter

摘要

A method for determining a pulse duration T₉₀ of a 90° pulse in a nuclear magnetic measuring method. A signal generator has a known generator resistance R_S, wherein a coil has a coil impedance Z_L with a coil resistance R_L and a coil reactance X_L, wherein a coupling circuit has an adjustable matching capacitance C_M and an adjustable tuning capacitance C_T, and wherein the medium has a Larmor precession having an angular Larmor frequency ω_P. The time needed for determining the pulse duration T₉₀ of the 90° pulse is reduced by the matching capacitance C_M and the tuning capacitance C_T being set so that the angular resonance frequency ω₀ corresponds to the angular Larmor frequency ω_P and by power matching being present between the signal generator and the coil. The coil resistance R_L is determined and the pulse duration T₉₀ is determined as a function of the coil resistance R_L.