INPUT-OUTPUT TESTS 53 



The input-output method of measuring efficiency 

 is subject to considerable inaccuracy. It is not recom- 

 mended and should not be used except under special 

 conditions. It is much more preferable to ascertain the 

 losses directly when reliable results are desired. By 

 adding all the losses to the output at any load, the 

 input for the load may be obtained, which, divided 

 into the output, gives the per cent efficiency. 



The resulting errors from the input-output method 

 are likely to be large, since any inaccuracy in meters 

 or readings influences the results directly. In loss 

 measurement tests, the same per cent error in meters 

 or meter readings influences the results of the efficiency 

 calculations indirectly. Consequently the latter method 

 is superior for accurate determinations. 



