Zero Method.—In electrical measurements, a zero method is one in which the arrangement of the testing devices is such that the value of the quantity being measured is shown when the galvanometer needle points to zero.
In the zero method either a contact maker or contact breaker may be used in connection with a galvanometer and slide wire bridge, as shown in [figs. 2,595] and [2,596].
Fig. 2,595.—Diagram illustrating zero method of wave measurement with contact maker. The voltage of the battery must be at least as great as the maximum pressure to be measured and must be kept constant.
Ques. What capacity of battery should be used?
Ans. Its voltage should be as great as the maximum pressure to be measured.
Ques. What necessary condition must be maintained in the battery?
Ans. Its pressure must be kept constant.
Ques. How are instantaneous values measured?