(2) Root-Mean-Square and Peak Value Calculations
Y o u r V T - 1 7 1 F V T - 1 7 1 E J , an voltmeter of absolute-mean
value indication type, reads root-mean-square values of
sinusoidal w a v e inputs. A l s o , it deflects the pointer in
proportion to the absolute-mean value of a given input
wave.
If the f o r m f a c t o r ( = root-mean-square v a l u e / a b s o l u t e
mean value) of the input wave and the crest ( = peak
v a l u e / r o o t - m e a n - s q u a r e v a l u e ) are known, then the
root-mean-square value and peak value can be cal-
culated a s f o l l o w s .
a . A s s u m e t h a t the meter reads V .
2
\Tl
• Absolute mean v a l u e = • V ^ 0.9 V .
TZ
• Root-mean-square v a l u e = ( A b s o l u t e mean v a l u e )
x ( f o r m f a c t o r ) .
• Peak v a l u e = (Root-mean-square value) x ( c r e s t ) .
b. F o r rectangular waves, their f o r m f a c t o r is u n i t y
(1) and the crest u n i t ( 1 ) .
2v
/
~2~
• Absolute mean v a l u e = - V ^ 0 . 9 V .
7C
• Peak v a l u e = 0 . 9 V .
c. F o r sawtooth w a v e s , their f o r m f a c t o r is 2 / v
/
3
_
and
the crest \ / 3 " .
• Absolute mean value = V ^ 0.9 V .
7T
• Root-mean-square value =
x - = V = - - ^ - V ^ 1.04V.
• Peak v a l u e = -
^
x
^ — 1 . 8 V .
7TV
3 %