188 



ELECTRICAL MEASUREMENTS 



-AAAA^ — II 1(— -^WT nm 



Resistor 

 R in ohms(ii) 



Capacitors 

 C in farads, 

 /ifd, or ixfjLf 



Inductance Inductance 



L in iron Transformer 



henries core 



+ 





Connected Crossing Ground 

 conductors or wires 



Switch 



Double-throw 

 switch 



H»- ^■|l|•- 



Fuse 



Cell 



Battery 

 of cells 



r\ <^ <^ <ty ^ 



Phototube Heater Meter Voltmeter Ammeter Indicator 



Gas- filled 

 tube 



Variable 

 capacitor 



filament 

 of vacuum tube 



lamp 



y^ -^WW- -AAA/v L -y>^ 



Potentiometer, 

 voltage divider 



Variable resistors 



-J--VVV-J- 



nm^ 



m X. 



RC filter LC filter Bridge 



Fig. 13-8. Commonly used symbols. 



Circuit diagrams 



Most electronic instruments are accompanied by instruction books 

 containing the complete circuit diagrams. These diagrams increase the 

 likelihood that the operator can maintain the instrument and make neces- 

 sary repairs and adjustments. Symbols have become more-or-less stand- 

 ardized, which makes the task easier. Figure 13-8 is arranged to show 

 some commonly used symbols as well as some representative circuit com- 

 ponents. An interesting and very instructive exercise is to draw a circuit 

 diagram by tracing the parts and connections of a finished electronic 

 device, even a radio. 



