Precautions in the use of standard instruments

The paper summarizes briefly the main precautions which should be adopted in the purchase, installation and use of electrical instruments which in a test department serve for calibrating instruments of a lower order of accuracy. The errors to which the potentiometer, dynamometer wattmeter, electrostatic voltmeter and moving-coil indicator are liable are considered, and means for eliminating or reducing such errors are pointed out. The author emphasizes the advantage of the method of discovering how errors may be produced, with the object of securing control of such errors. The conclusion is reached that, although preliminary investigations may be somewhat tedious, the result of due precautionary measures is increased all-round efficiency.