Tektronix 2247A Operator's Manual page 40

·. ,o
Operators Familiarization .
(TO RISE/FALL MENU)- selects the rise/fall measurement menu.
In this menu, the top two Items are the actual measurements. Only
one of these two may be selected at a time. When a measurement Is
selected, the peaks of the signal are automatically measured, the
trigger levels are set (as described below), and the measurement
starts.
RISE
FALL
TRIG 10-90
TRIG 20-80
I+-
SET REF~
Rise/Fall menu
The next two menu Items determine how the rise/fall trig levels are set ;
only one of these two may be selected (underlined when selected) .
When TRIG 10-90 Is selected, the rise or fall measurement will trig ger
at the 10% and 90% points between the positive and negative peaks of
the waveform. Selecting TRIG 20-80 will cause the measurement to
use the 20% and 80% points.
The I+- SET REF -+I Item toggles on (underlined) or off each time It
button Is pushed. When on, the I+- 0% and 100%-+! cursors will appear
for manual adjustment of the rise/fall reference levels. When toggled
back off again, the rise/fall measurement will resume , using these new
levels to calculate and set the 10%-90% (or 20%-80°/ e ) trigger level .
RISE measures the rise time of either CH 1 or CH 2. When thl
measurement Is first selected, the peaks of the signal are measur d
and stored as the 0% and 100% reference levels. Then the 10% nd
90% trigger levels are calculated and set from the reference lev I ,
and the time Interval Is measured and displayed. During RISE/FA L
measurements, all B Trigger mode, source, and coupling LED s r
turned off, and these parameters may not be set. The B Trigger I v I
may not be adjusted; when A is selected, the usual modes , slop ,
couplings, and level may be controlled. B Trigger SLOPE Is also not
settable. B SLOPE LED will be on If doing a RISE measurement and off
If doing a FALL measurement.
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2247 A Oper
tor
I
Operators Familiarization
FALL measurements are the same as RISE, except that the fall time Is
measured .
The following error messages are possible during RISE and FALL
measurements:
Message
NO A SWEEP
NO START
NO STOP
NO RISE
NO FALL
>100s
CHANGE A
CPLG
INCREASE
SIGNAL
AMPLITUDE
MEAS SOURCE
INPUT IS
GROUNDED
MEAS SOURCE
VAR OUT OF
DETENT
2247 A Operators
Reason
No A sweep was detected after timeout.
No start trigger was detected.
No stop trigger was detected.
No rising edge was see~ by C/T during a rise time
measurement, after timeout.
No falling edge was seen by C/T during a fall time
measurement, after timeout.
Time lnterval greater than 100 seconds (timeout
disabled).
A Trigger CPLG set to NOISE REJ (not allowed,
because this would caus~ Incorrect measurement
triggering) .
.
Source signal's pk-pk amplitude ls too l~w '
for accurate rlse/f all measurement; shoufd be at
•
least 4 divisions.
This message Is shown If th_ e source
coupling Is set to GND.
Trigger levels cannot be computed correctly
unless attenuator Is calibrated.
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