The central question is surely: how much "light" is emitted by a lamp, and in what direction? The luminous intensity that must be emitted from different angles by the lamps is a point that arises in all regulations. Since the luminous intensity is derived from the illuminance and the measuring distance, and the measuring distance has a decisive influence on the accuracy of the measurement, it is appropriate to choose a measuring distance that is as large as possible. In the case of weak light sources, however, the sensitivity of the sensors may be insufficient, which means that a smaller measuring distance is to be preferred. Luminous intensity as a function of both the horizontal and the vertical angle is measured with a goniophotometer. There are several ways of constructing a goniophotometer. With the goniophotometer used at Pintsch, the lamp is mounted and adjusted on a holding plate. The holding plate then revolves around the verticle or horizontal axis of the lamp. The sensor is placed in front of the lamp at the appropriate distance. A computer controls the goniometer movement and the measuring sensor. The size of the objects to be measured and their maximum weight is limited by the design principle of the goniophotometer. The optical laboratory therefore possesses a second, manually operated goniophotometer. To ensure that only the light from the lamp itself is measured, the measuring area must be blacked out. Reflections on the walls, the ceiling and the floor must be suppressed as far as possible. In the Pintsch Bamag optical laboratory, ceilings and walls are therefore painted a dull black. Three curtains and an additional light-suppressing cover on the floor reduce the stray light further.

A particularity in lamp measurement are lamps that do not radiate a constant luminous intensity but emit flashes - such as omnidirectional beacons, hazard warning lights, or beacons for lighthouses. These lamps cannot be measured with a normal goniophotometer. They necessitate the use of a special flash-measuring instrument, which scans the flash very quickly, records it, performs the necessary evaluation of the results, and calculates the effective luminous intensity.
Another point that plays a role in most regulations is the colour of the emitted light. The colour is defined in accordance with DIN 5033. This involves the marking all all visible colours by two coordinates (x and y). The coordinate system is constructed in such a way that the colour location of the mixed light of the light of two colour locations lies on the connecting line between the two colour locations.

There are several ways of measuring colours. In the Pintsch Bamag optical laboratory the spectral method according to DIN 5033 - 4 and the three-range method according to DIN 5033 - 6 are used.
When the spectral method is used, the entire range of the visible light is scanned and thus the spectrum of the light source is recorded. The spectrum is evaluated with the sensitivity of the human eye and the resulting colour is calculated. When the three-range method is used, this evaluation is performed by means of one or several filters.

The next question is the question of how much "light" an illuminant emits. The so-called
luminous flux can be measured with an Ulbricht sphere photometer. To do this, an illuminant with a known luminous flux is placed in the sphere photometer and the lumininous intensity measured behind a screen, which prevents light from falling directly from the illuminant onto the sensor. The illuminant to be inspected is then attached at the same position and operated. From the luminous intensity now measured and the values of the previous measurement, the luminous flux of a lamp can be measured. Other measurements that can be made with an Ulbricht sphere photometer are efficiency measurements of reflectors, colour measurements and transmittance measurements.

In the Pintsch Bamag optical laboratory, three Ulbricht sphere photometers are available for use.
The luminous-intensity measuring instruments of the photometers are too unwieldly for measuring luminous intensities e.g. in railway vehicles. The light laboratory therefore possesses a handheld luxmeter as well.
Phantom light suppression plays an important role especially in the case of signals. The signals must be designed in such a way that, as far as possible, light shining from the low-lying sun on the signal does not emerge from the signal and deceive the observer into believing that the signal is switched on. To perform the necessary measurements in this case, a luminance measuring instrument is required. To generate a defined luminous intensity e.g. for the adjustment of twilight switches, a luminous intensity standard is required.

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