# Laboratory Assessment of In-Pavement Airport Lamp's Luminous Intensity Distribution
## 4 Photometric Quality Investigation of a Light Sensor  
During the measurement of the photometric characteristics of an airport lamp, according to the recommendations, the luminous intensity of the main light beam should be checked. For this task, sensor modules based on a photodiode can be used [17], from which the results obtained, after appropriate conversion, can indicate the value of the luminous intensity. Sensors of this type are resistant to the influence of the angle of incidence of light on the obtained intensity values [21], and they show very good dynamic properties during measurements [22]. The GY-302 module that uses the BH1750 sensor for measurement has a range from 1 to 65,535 lx, and the shape of its spectral response corresponds to the shape of the spectral response of the human eye. It is a digital module with a resolution of 16 bits and communicates via the I\({}^{2}\)C interface. It can operate in three different modes, which differ from each other in measurement time and resolution (Table 1). It should be noted that the measurement times in individual modes may differ from those listed in Table 1 because, with the increase in the size of the transmitted measurement value, the time is proportionally extended. In the case of measurements in H-Resolution modes, according to the documentation, the measurement time (integration time) is long enough to eliminate the influence of 50/60 Hz noise [23]. An important aspect in the context of measuring the photometric characteristics of airport lamps is the repeatability of the obtained measurement results. The navigation lighting lamps operate in five different modes, differing from each other in the illuminance level, which is regulated by changes in the current intensity of the power supply system; the exact values are presented in Section 5. Taking these conditions into account, an experiment was carried out consisting of making a series of 10,000 measurements using the GY-302 module with a BH1750 sensor for the brand new touchdown zone lamp IDM 4671, changing its power modes and changing the illuminance sensor operating modes. To ensure that the obtained values of illuminance are correct, a Sonopan L-200P certified luxmeter measurement was also taken [24]. The photometric distance was assumed to be consistent with the length of the goniometer arm, which is 1 m. Figures 6a, 7a, 8a, 9a and 10a show the measured illuminance values and statistical box plots in Figures 6b, 7b, 8b, 9b and 10b. \begin{table}
\begin{tabular}{c c c} \hline
**Measurement Mode** & **Measurement Time (ms)** & **Resolution (lx)** \\ \hline L-Resolution Mode & Typ. 16 & 4 \\ H-Resolution Mode & Typ. 120 & 1 \\ H-Resolution Mode2 & Typ. 120 & 0.5 \\ \hline \end{tabular}
\end{table} 
Table 1: BH1750 measurement modes [23]. Figure 6: Measurements of illuminance in the 28A power mode: (**a**) linear chart; (**b**) statistical chart. Figure 8: Measurements of illuminance in the 4.1A power mode: (**a**) linear chart; (**b**) statistical chart. Figure 10: Measurements of illuminance in the 6.6A power mode: (**a**) linear chart; (**b**) statistical chart. Figure 7: Measurements of illuminance in the 3.4A power mode: (**a**) linear chart; (**b**) statistical chart. Figure 9: Measurements of illuminance in the 5.2A power mode: (**a**) linear chart; (**b**) statistical chart. For the measurements taken, the mean value, median, and standard deviation were determined, as shown in Table 2.  
The analysis of the data in Table 2 shows that with the increase in the value of the lamp supply current, and thus the measured value of the illuminance, the differences in the mean value of the measurement between the various operating modes of the sensor also increase. The median values also have a similar tendency; however, the values of the standard deviation remain at a level which, in relation to the measured illuminance, constitutes its small percentage in the case of high current intensities.