Fig. 3. x chart stability comparison of BLUE RADIODMETER at different experiment days. (a) Diaphragm calibration method. (b) ND-filters calibration method. Fig. 4. R chart stability comparison of BLUE RADIODMETER at different experiment days. (a) Diaphragm calibration method. (b) ND-filters calibration method. Experimental Results and Discussion The irradiance measurements of the two applied calibration methods for one of the two test detectors are shown in Fig. 3 and Fig. 4. In Fig. 3b, x chart of BLUE RADIODMETER, shows that there is no indication of an out-of-control condition in the case of the ND-filters calibration method, while there is more than an out-of-control condition in the other case, the diaphragm calibration method (Fig. 3a). Fig. 3 clarifies that all the fluctuations are around the mean X and t 1he changes i xi N due to random error are controlled and satisfied in the ND filter calibration method, i.e., the control limits on the x chart are N October 2022 Fig. 5. BLUE RADIODMETER comparison of repeatability STDEV at all experiment days in the stability of calibration method for diaphragm and ND-filter. IEEE Instrumentation & Measurement Magazine 23