RELAY MEASURING EQIII'MKNT 



Fig. 13 — Schematic of sliado\vgrai)h action 



graph mentioned alcove, has on many occasions been modified to also 

 record a silhouette of the moving parts of the structure on a moving 

 strip of photographic paper, and thus pro\'lde a simultaneous trace of 

 displacement and current against time. One of the more advanced 

 shadowgraph-oscillograph e([uipments is shown in Fig. 13, and a typical 

 record made on a wire spring relay is given in Fig. 14. In this case the 

 single record shows the current to the winding and the mechanical move- 

 ment at the two opposite ends of the contact-operating card attached to 

 the armature of this relay. From such measurements, ^'elocities of im- 

 pact, location of the parts at a given instant, stagger between parts, 

 relative motion, unbalanced motion, and the like, may all be determined 

 and correlated with electrical changes. 



Motion of parts may also be studied optical!}' to give displacement or 

 velocity data, using the photocell. Properly placed flags on the moving 



CARD MOTION ■-^--, 



TOP OF CARD >■ 



BOTTOM OF CARD-*" 



CORE MOTION ^-j 



WINDING CURRENT—-' 



4 H 



^ 10 1^ 



MILLISECONDS 

 Fig. 14 — Typical shadowgram of 2S7 relay armatiiro motion. 



