A manual of home-making

iaspection may result in the reading l^eing made as 548 kilo- watt hours. However, the index of the units' dial standing on the figure 8 -sliows that it has not quite completed a revolution, and honre that tlie index of the fsecond dial (if it is properly set on its shaft) ssliould I>e rlo.se to a ihvision and al>otit to reach it. Hence, it should be reatl lus having passetl the 3 anil nut having reached the 4, A view of a meter dial face having the KILOWATT MOUR5 Flo. 44.— Dm! of u wntthour meter. In tfib dial the Jiinid on tbi^ second rirrk* from ibv riiilit ts tiUghtly in iidvarire of ha proper position on its t^hnfi. The rending is thcfuiitic as in Fi^. 43, niimely, 538 kilowatt hours, although at u glance it might lie iiicorrt'ttly rcjuJ oh 548 kilo- watt houra« Fserond index to the left slightly displaced in this way m shown' in Fig. 41. When one that hand jwints to 9, special care must he taken that the dial hand of the next hip;her dial is not read too high, as it may appear to have reaehetl the next nuoilxT» but will not have done so until the dial hantl at 9 has come it) 0. A sim- pie illostratiou will make 1 his clear. If the hour liand of a rlock points to 10, as closely sm can be read, and if the clock had no minute handj the time would be read us 10 o'clock. If the niin* ute hand, however, is pointing to the figure 11, the time Is read as 9.55* Ten minutes later the hour lumd may not have moved perceptibly, hot the time is now read as 10.05. Sim- ilarly, in the electric meter, the reading of each dial must l>e interpreted by noting the reading of the next dial to the right. The dial hands on adjacent dials revolve in opposite direc- tions; therefore, a reading .should always Ix^ checked iifter being- written down, as it is easy to mistake tlic direction of rotation. I HOUSEHOLD MEASUREMENTS AND THEIR USE 149 Checking Oie wailhour meter. The eler-tric mvAar may be checked approximately by the hotLsehoIdtT witiiout the use of electrical instrument's. For this purpose it is only necessary to note the reading of the meter, then turn on a number of lamps azid note ilie time in hours re- quired to cause the index of the dial farthest to the right to ad- vance one division. It Is necessary to use lamps which are rated in watts, as is done with most incandescent lamps now made. If the meter is niotlern, it will have a dial marked "kilowatt hours," and one division on the dial farthest to tlie right is a kilowatt hour, which means 1000 watt hours. For example, if 10 lamps, each marked 25 w^atts, are lighted at a given time, the rate of using electrical energy is 10x25 =250 watts. In 4 hours these lamps will use 4x250=11300 watt hours, and this should cause the index of the dial farthest to the right to ad- vance one division. As it is not possible to read a single (;h\ision aecuratel3^ the lamps may Ix* allowed to run until the index has moved over several divisions. If more lam|)s can be turned on, or larger lamps used, the time required for the test will be re- duced. The preceding test is approximate but will settle the question of whether any large error exists in the meter. To make an ac- curate test requires portable watt hour meters or other electrical apparatus which is suitable for use only Ijy uieter inspectors.