Front Panel Operation
2-61
Semi-synchronous operation
In the Semi-synchronous Trigger Link mode, all triggering
(input and output) is controlled by a single line. When the
normally high (+5V) trigger line is pulled low (0V), a trigger
occurs on the negative-going edge. When the trigger line is
released, a trigger occurs on the positive-going edge (see
Figure 2-26). The advantage of this single line trigger is that
as long as one of the instruments in the system holds the line
low, the trigger is suppressed. In other words, the trigger
does not occur until all instruments in the system are ready.
Figure 2-26
Semi-synchronous Trigger Link specifications
ª +5V
Trigger on
negative-going
edge
Trigger on
positive-going
edge
Pulled low by
source instrument
Released by
acceptor instruments
0V
For example, assume that a Model 2002 is connected to two
Model 7001 or 7002 Switch Systems for semi-synchronous
operation, as shown in Figure 2-27. All three instruments are
programmed to use trigger line #1. The two Model 7001s/
7002s have relay settling times of 10msec and 50msec, re-
spectively. The Model 2002 is designated as the trigger con-
trol source and the two Model 7001/7002 units as trigger
control acceptors.
Assume that the Model 2002 initially performs a measure-
ment. After the reading is done, the Model 2002 drives the
trigger line low. The negative-going edge triggers both Mod-
el 7001s/7002s to close a channel. While the Model 7001s/
7002s are in the process of closing a channel, they hold the
trigger line low. Ten milliseconds after switch closure, the
first Model 7001/7002 releases the trigger line. However, the
second Model 7001/7002 continues to hold the line low since
it is not finished. Fifty milliseconds after switch closure, the
second Model 7001/7002 releases the trigger line. The posi-
tive-going edge triggers the Model 2002 to make a measure-
ment and subsequently pull the trigger line back down to
close the next channels. This process continues until all
channels are scanned and measured.
Figure 2-27
Typical semi-synchronous mode connections
Trigger
Link
IN
OUT
Trigger
Link
7001 or 7002 Switch System
Trigger Link
Cables (2)
(8501)
2002 Multimeter
IN
OUT
Trigger
Link
IN
OUT
Line #1
Line #1
7001 or 7002 Switch System
Содержание 2002
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