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J I
6.4. 1.3. Decibel measurements (dBV-)
G E N E R A L
T h e d B f u n c t i o n o f f e r s t h e p o s s i b i l i t y t o m e a s u r e t h e r a t i o b e t w e e n a c v o l t a g e s , a n d t o e x p r e s s t h i s i n d e c i b e l s
( d B ) . D e c i b e l m e a s u r e m e n t s c a n b e m a d e i n t w o w a v s v i z . :
-
d B m e a s u r e m e n t s ( S t a n d a r d m e t h o d ) ,
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d B m e a s u r e m e n t s i n r e l a t i v e r e f e r e n c e m o d e .
T h e r e l a t i v e r e Í e r e n c e m o d e e n a b l e s s e l e c t i o n o f a p r e d e t e r m i n e d r e l a t i v e r e f e r e n c e z e r o l e v e l . E a c h s u b s e q u e n t
r e a d i n g w i l l i n d i c a t e t h e p o s i t i v e o r n e g a t i v e d e v i a t i o n f r o m t h e r e l e v a n t r e f e r e n c e v a l u e .
E x a m p l e :
0 . 1 V r y
1 0 V r u
1 C V t u
0 . 1 V t u
s T 3 0 1 1 .
Fig. 14. dB measurements
F U N C T I O N
A M P L I F I E R
I N
O U T
d B
d B
Z E R O S E T
1 0 0 . 0 0 m V
- ' t 7 . 7 d B
0 0 . 0 d B
1 0 . 0 0 0 v
+ 2 2 . 2 d B
+39.9 d B
A T T E N U A T O R
I N
O U T
1 0 . 0 0 0 v
+ 2 2 . 2 d B
0 0 . 0 d B
1 0 0 . 0 0 m V
- ' t 7 . 7 d B
- 3 9 . 9 d B
d B M E A S U R E M E N T S ( S T A N D A R D M E T H O D )
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S e l e c t f u n c t i o n V - w i t h t h e f u n c t i o n s e l e c t o r .
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S e l e c t t h e a u t o m a t i c r a n g i n g m o d e w i t h p u s h b u t t o n A U T O / M A N * .
R e m a r k :
Manual ranging is indicated with a * on the disptay. In automatic ranging mode the UP level is 20200 and the
D O W N l e v e l i s 0 1 8 0 0 .
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c o n n e c t t h e v o l t a g e s o u r c e t o t h e 0 a n d V t e r m i n a l a n d m e a s u r e t h e v o l t a q e .
R e m a r k :
Take care that the maximum input voltage of 600 V rms is not exceeded.
6 0 0 V r m s = + 5 7 , 8 d B .
D e p r e s s p u s h b u t t o n d B ( V - ) o n c e .
R e m a r k :
ïhe measured ac voltage is now expressed in decibels (dB).
0 dB = 1 mW, 600 í2O,775 V is used as reference
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T o l e a v e t h e d B f u n c t i o n a n d t o j u m p t o t h e V - f u n c t i o n a g a i n , d e p r e s s p u s h b u t t o n d B ( V - ) t w i c e .
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