A new system which combines two independent diagnostic devices on the same line of sight is used to measure the X-ray spectrum in the 50-1000 eV regime. The first device is an array of six channels of time-resolved X-ray diodes (XRD's), arranged to cover the spectral band with low spectral resolution (λ/Δλ ∼ 3). The second device is a time-integrated sinusoidal transmission grating spectrometer (STGS) with a wide spectral range coverage and moderate spectral resolution (λ/Δλ ∼ 30). The spectral band of each XRD can be tuned by selecting a cathode, an x-ray mirror, and a filter. The novel sinusoidal shape of the STGS allows acquisition of a pure first-order spectrum without contribution of high dispersion orders, resulting in a higher accuracy spectrum measurement. The system described here has recently been used [Y. Ehrlich et al., Rev. Sci. Instrum. 88, 043507 (2017)] to demonstrate an improved unfolding algorithm of an XRD-acquired spectrum, achieved by experimental information gathered from the STGS measurement.