BS-EN-379 pdf free download
BS-EN-379 pdf free download. Personal eye-protection — Automatic welding filters.
5.2.1.2 High speed optical shutter A device capable of switching on the switching light source at a speed meeting the requirements of 5.2.2. 5.2.1.3 Light source for the measurement of luminous transmittance A source of standard illuminant A (see ISO/CIE 10526). 5.2.1.4 Light detector and recording apparatus A device capable of detecting and recording the light from the measurement light source transmitted by the welding filter. 5.2.2 Performance of test equipment Check that when the light beam is switched by the high speed shutter, the rise time between 10% and 90% of the light transmitted by the shutter is no greater than 10% of the switching time required for the scale number difference to be measured. See Table 4. 5.2.3 Measurement Maintain the test specimen at the appropriate test temperature for a minimum of 2 h before testing and during the period of the test. Set up the measurement light source (5.2.1.3) and the test specimen so that the plane of the test specimen is at (90 ± 5) o to the measurement beam. With the switching light source on, switch the high-speed shutter to allow the light through to the test specimen, thereby switching the test specimen to its darkest state. Record the measurement light transmitted through the test specimen during the switching period. 5.2.4 Calculation Calculate the switching time t s from the equation given in 3.5, with t = 0 as the time when the illuminance at the test specimen reaches a level between 40 and 60% of the value given in 5.2.1.1. 5.3 Scale number setting of welding filters with automatic scale number setting 5.3.1 Test equipment High-pressure xenon lamp as source of radiation producing a variable illuminance. 5.3.2 Measurement of the scale number setting a) Set up the light source of 5.3.1 and the test specimen so that the plane of the sensor field of the test specimen is at (90 ± 10)° to the light beam including the divergence of the beam. b) Determine the luminous transmittance at the illuminance applicable for the scale numbers according to the formula given in 4.3.2.5 (a) respectively in Table 2 within the range specified by the manufacturer. The tolerance of the illuminance values shall be ± 10 %. Perform the measurements at (-5 ± 2)°C and at (55 ± 2)°C and check if the requirement of 4.3.2.5 (b) is met. c) Determine the luminous transmittance at (23 ± 5)°C and at the illuminance applicable for the scale numbers according to the formula given in 4.3.2.5 (a) respectively in Table 2 within the range specified by the manufacturer. The tolerance of the illuminance values shall be ± 10 %. Calculate the scale number from the luminous transmittance. Plot a graph of scale number against illuminance and check if the requirement of 4.3.2.5 (a) is met. d) At double the illuminance value applicable for the darkest state scale number, check that the luminous transmittance of the filter corresponds to the range of the darkest state scale number. Perform the measurements at (23 ± 5)°C and check if the requirements of 4.3.2.5 (c) and (e) are met. Note In the preceding section “darkest state scale number” means the highest scale number specified by the manufacturer. 5.4 Spectral sensitivity of welding filters with automatic scale number setting 5.4.1 General Two methods are described in this section. Alternatively, any equivalent method may be used. Measurements shall be carried out at (23 ± 5)°C. Set up the light source for the scale number setting and the test specimen so that the plane of the sensor field is irradiated by the light beam with an illuminance in the range of the automatic scale number setting. 5.4.2 Method using monochromatic radiation a) Irradiate the sensor(s) for the automatic scale number setting with radiation in the wavelength range between 400 nm and 900 nm having a spectral bandwidth not greater than 50 nm and determine the irradiance at the sensor (SI unit: W/m²); b) Reduce this irradiance until the lowest scale number of the dark scale number range of the filter is just set; c) The reciprocal of these irradiance values, as determined in 5.3.2 (c), gives the spectral sensitivity curve in dependence on the wavelength.BS-EN-379 pdf download.
