HP 5335A - Page 37

Operation and Programming
3-100. To measure the frequency of a pulsed stream, use the AUTO TRIG mode and dc
coupling. AC coupling these types of signals tends to distort them slightly, due to the charging
of the coupling capacitor. Additionally, the position of the signal on the zero preset trigger level
is determined by the average dc level of the input. Depending on the pulse width and duty cycle,
this dc average may be low enough to allow the base line noise to trigger the counter, producing
extra counts.
DUE TO
ACCOUPLING
INPUT
AC COUPLED
TRIG
LEVEL
\
1 1 1 ! i i I 1
1
!
!
1 1 ! i 1 1 1 1 1
r
! i ! 1
!
I ! 1 1 !
i
1
1
_i__
- VWVVWAVVWWWi
/VVwvVA'WVWWvj
kwvVVVvVAWvV
i i
OV
BASE
LINE NOISE
HYSTERESIS
BAND
3-101. DC coupling “fixes” the dc level of the input signal. Using AUTO TRIG in Preset or
Adjustable allows the trigger level to be easily positioned at an optimum point.
AUTO
TRIG
OV
—
. -
1 1 1 1 ! ! 1
-
1 1
1 1 1 t 1
-
I 1 1 1 1 1
ANVWWVA*
<VyVWWAVWWvv
-•
- ■
VvWWWvV _
BASE
LINE NOISE
HYSTERESIS
BAND
3-102. TIME A - B
3-103. The TIME A-~B mode measures the time interval between a start signal at Channel A and
a stop signal at Channel B. The START and STOP slopes, as well as trigger levels, are individually
selectable. If the START and STOP signals are to be derived from a single signal, set the INPUT
SEPARATE/COMMON key to COM A.
3-104. When TIME A—B is selected, the 5335A automatically shifts the GATE MODE from
NORM to MIN (NO DELAY). If a “delay” (stop channel prevented from triggering for a specific
period of time) is desired, the NORM, FAST, or MANUAL gate modes may be selected. When the
delay is active, the red DELAY indicator will fight.
3-105. For a simple time interval measurement with both slopes set to positive, the counter will
display the time period illustrated above. If the signals are not repetitive, be sure that AUTO
TRIG is off.
CHANNEL A
CHANNELB
TIME
MEASURED
3-21
Model 5335A