MEASURING SMALL TIME INTERVALS 349 



In order to avoid the necessity of correcting the measurements for the 

 error in the bridge, a value of resistance corresponding to the error may 

 be connected permanently in series with Ri. This should be made 

 variable if a high degree of accuracy is desired, because the operating 

 time of the two relays in the bridge may change slightly from day to 

 day and small readjustments of the resistance will, therefore, be 

 necessary. 



The sensitivity of the bridge, that is, the ease with which small 

 intervals of time can be distinguished by the deflection of the meter, is 

 dependent upon the sensitivity of the meter, the voltage of the common 

 charging battery, the value of capacity, and the ratio of the capacity 

 of the large condenser to that of the small condenser. With a par- 

 ticular type of meter, the larger the voltage, the condenser capacities, 

 and ratio of condenser capacities, the more sensitive will be the bridge. 



Although the chief use for the bridge up to the present time has been 

 in connection with voice operated relay devices, its future use will 

 undoubtedly be extended to other fields. Some indication of the uses 

 to which it might be put may be obtained from the following suggested 

 applications. 



1. For measuring the functioning tirnes of electromagnetic switching 



arrangements in various kinds of communication and signaling 

 systems. 



2. For measuring propagation time at different frequencies over 



telephone circuits and "lag" in telegraph instruments and 

 circuits. 



3. For studying the operation of a machine with a view to improving 



it by measuring the speed of operation of various parts and the 

 relative time of operation of certain parts with respect to other 

 parts. Electrical contacts would have to be provided tempo- 

 rarily at suitable places on the machine. 



4. For maintaining the proper adjustment of time-limit over-load 



relays, circuit breakers, etc., on power circuits. 



5. To determine the rate of acceleration of motors or other machinery 



by employing a suitable centrifugal contact arrangement. 



6. In psychological tests for determining whether the time of response 



of a person to a particular signal is above or below a required 



value. 

 Numerous other applications to laboratory and field work might be 

 suggested where such a time measuring device could be employed to 

 considerable advantage. The cases mentioned above are not neces- 

 sarily the most practical but they serve to illustrate the capabilities of 

 the device as described or when provided with simple modifications. 



