HP 4262A Operating And Service Manual page 239

Section VIII
A14 BOARD CIRCUIT DESCRIPTION.
Model 4262A
In a 10kHz measurement, the four phase generator
output is fed to the 1/10 down counter whose
output is inputted to gate circuitry U13. The U13
output is a Imsec (1kHz) pulse train which drives
the sampling switch Q5 at a rate of once in 20
periods of the period averaging circuit input (phase
detector output) signal. The periodic rate is
sufficient for period averaging of the high fre-
quency input signal.
INTEGRATOR NULL OFFSET CONTROL.
Phase
Detector
uio ul4 vl
N L+ PHASE 3R/2 eret - t
Low oSS L
VO
H9—O
4t
| 4 prase
—+ PHASE
T
ue | T i | ]GENERATOR g ::fig J";/2
-
et I r
| I uis
Q O | 1710 DOWN {-
l counter [ 1
LE—J
-+ us JL 7ps
ui3 | |
| _{o-l—' Sob?oET + To period
L o averaging
_ circuit QS
In a 10kHz measurement,
active switches U13 and
U14 change their states.
8-56 .
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