Illustration of the determination of the global measurement errors in low spectral resolution in the L band with the ATs. Top: visibility fundamental noise standard deviation (σ_F in grey), flux dependent error due to the broadband photometric error (σ_P in yellow), broadband calibration error (σ_C in cyan), and their combination (σ in red). Middle: same for the closure phase, without σ_P. Bottom: differential phase fundamental noise standard deviation (σ_F in grey).