938 THE BELL SYSTEM TECHNICAL JOURNAL, JULY 1954 



may be put on the vertical plates. The chatter of 16 contacts may also 

 be observed at one time to obtain a ciuick check of the contact per- 

 formance. Operate and release times of the contacts may be read directly 

 from the scope if a pip is put on the vertical axis when the test relay coil 

 is energized. The front end of the relay is clamped for all measurements. 

 Switches are pro\dded to select different combinations of contacts 

 to be checked with either a time base horizontal sweep or with the ar- 

 mature displacement as the horizontal sweep. 



DISCUSSION 



The electronic relay tester was designed primarily for rapid inspection 

 of wire spring relays. It provides a means for observing the position of 

 the armature for the operation of all contacts simultaneously while 

 the relay is pulsing. This method has several advantages over thickness 

 gauges which are frequently used: (1) The contacts are gauged under 

 conditions of use, that is, the armature moves as in normal operation 

 without touching the gauging device; (2) Inspection is more rapid since 

 the go-no-go positions are displayed on the scope face. Relaj^ spring 

 combinations requiring a sequence of contact operation are readilj^ 

 observed while the relaj^ operates in a normal way; and (3) When relaj^ 

 adjustments are made the results of the adjustment are shown im- 

 mediately so the contact operate points are centered within the desired 

 range giving more margin for changes that may occur with use. This 

 de\dce is readily changed to measure other relaj^ characteristics that may 

 be of interest such as operate or release time, contact chatter and arma- 

 ture rebound. 



ACKNOWLEDGMENTS 



The authors are indebted to J. H. McConnell who designed a similar 

 electrostatic transducer and to R. L. Peek, Jr., who derived the equa- 

 tions for it. Mr. Peek also suggested the method used in the scanning 

 circuit. 



