332 Appendix D Optimizing Throughout and Reading Rate
Measurement List The most efficient method of using the 3458A within a system is to establish a
measurement list in Program Memory that corresponds with a channel list in the
signal switching instrument. The 358A's External Output is connected to the
Channel Advance input of the switching instrument and the Channel Closed
output of the switching instrument is connected to the External Trigger input of
the 3458A. Regardless of how long it takes to close a channel or make the
measurement, the channel is always closed and the measurement is always had
time for completion without programming additional WAIT statements or added
delay. Further, the reduction in GPIB data messages results in faster, more
convenient programming. In the Figure 48, the circuit is tested to show the
interaction of the 3458A with a switching unit, the 3488A, using External Trigger
and External Output. The measurements are simple AC and DC Volts and
resistance. In this case, the time to change a function or a range is important to
the test set-up because the channel closure is relatively slow (the 3488A uses very
versatile, but slow armature relays with switching speeds of about 25 ms per
channel closure); therefore, multiple measurements are made on a test point. If
reed relays were used, it would be generally faster to change test points and stay
on the same function if the test situation allowed.
Figure 48. Measurement
list and scan list increase
test throughput when
used with External
Increment tied to
External Output and
Channel close tied to
external trigger.
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