advantest corporation TR5821 - Measurement a Ccu Ra Cy

5-3. M e as ure m e n t A ccu ra cy
5 -3 -1 . F re q u e n c y M e asu re m e n t (F R E Q . A , C)
T he m e as u re m en t m e th o d e m p lo y e d h ere c o u n ts th e n u m b e r o f re p e titio n s
o f th e signal to be m ea su re d p er u n it tim e a n d d isp lay s it as th e fre q u e n cy
(c /s = H z). As a c o n se q u e n c e, th e q u a n tiz a tio n e rro r o f ±1 c o u n t as sh o w n
b elo w o cc u rs in th e le ast s ig n ifica n t dig it.
Signal to be measured
Measurement gate A
Measurement gate B
Counting by gate A
Counting by gate B
T his is e xp resse d as fo llow s:
f * T = ± L S D o f th e d isp lay
I X ^ 1 G
w h ere : f x = M easured fre q u e n c y (H z )
T g = G ate tim e (s)
T h e a cc ura cie s fo r d iffe re n t fre q u en c ie s a n d gate tim es are sh ow n b elo w .
F R E Q . C uses a d iv id e -b y -tw e n ty p re sc a le r; th e acc u ra cy is re d u c ed b y 1
digit fo r th e sam e gate tim e .
I I ....... I I I I I I I I I
ft ta - L
il- TB --L
1111II ......... II
11111 111 11 111
Ta -TB
- 14 counts
-1 3 counts
5-7