Experiemnet on Properties of Materials

1.0 Aim

To determine the illuminance of a room using a photocell illuminance and carrying out a survey of the artificial lighting provision in the room by reference to the horizontal illuminance on the working plane

1.1 Apparatus

Photocell illuminance meter, measuring tape

2.0 Method

All the lights from the external windows were reduced by the dropping down of the blinds.

one person from the group was designated to record the readings called out from the various measurements from the tape and photo cell illuminance meter done by the other group members ,with tasks roles swapped as the experiment proceeds in no particular order

The dimensions of the room were taken, that is the length (L) and width (W) of the room and recorded.

the mounting height of luminaire (H_M ) was measured which is the height from the desk to the lamp

the room index was determined with the formulae (RI)=(L×W)/(L+W) H_M

the number of grid points required for the accuracy and the calculated room index was mapped up from table 1

The room was divided into equal grids based on the dimension of the room measured previously. The measurement points where marked up using a marker ensuring the spacing

Between measurement points is uniform in both directions. The measurement points was then marked out by marker

The illuminance meter was then used to take the measurement at each grid intersection by placing the light meter at the correct intersection of the grids and taking the measurements, ensuring that that person taking the reading is not blocking the view of the lighting system .the results recorded in a tabulated form as in table

3.0 Results

Table 1: shows results of measurements at each grid point

Measuring plane height 1.72m

Room dimension X: 9.5 m Y: 9.5m

Actual grid steps 1.58m ↓y windows

144 301 304 329 287 182

197 423 450 429 369 243

230 462 511 510 488 246

253 431 479 495 454 231

217 440 469 497 458 250

227 416 462 460 419 211

Total 1268 2473 2675 2720 2475 1363

← X widows

Table 2: WHAT DOES THIS TABLE SHOW???

← 9.5 →

Table 3: showing the final results of the survey

Average illuminance System efficacy Lamp efficacy

360.6 Lux 44.3Lm/W 87.8 Lm/W

4.0 Conclusion

It can concluded that there was a difference between the system efficacy which was 44 .8 and the lamp efficacy which was 87.8.This could have come about as a result of the age of the installation and the maintenance of the installation making the light output from the lamp being minimized, room surfaces becoming dull eventually ,luminaries becoming dirty which makes light available to the work plane deviate from the target value as a result.

Other factors that could have contributed to the variations in the efficacies could have been poor maintenance of surface reflectance, mains voltage variation, lamp operating temperature and the reduction of the light output as time passes because of the depreciation of lumen.

According to fact file number 3 task uniformity measurements and calculations are needed which is the usually