Keysight Technologies 3458A Guide D'utilisation page 447

AC current
AC current measurements are made strictly through the analog ACV section with
the voltage input being supplied by the DCI shunts. While there is no real decision
to make regarding the mode of ACI measurement, you can decide to accept less
accuracy and speed up the reading rate by decreasing the integration and settling
time. As a rule of thumb, the AC to DC converter needs at least 10 cycles of the
input wave form to give representative rms measurements. Hence, the frequency
of the input has a direct impact on the reading rate. Characterization of the 3458A
may be necessary to fine tune the measurement throughput for either ACV or ACI
to fit your application.
Frequency and period
The track-and-hold path is also the route the signal must take for frequency and
its reciprocal, period. The 3458A offers frequency response from 10 Hz to 10 MHz
to 7½ digits with a maximum gate time of 1 second. One can trade speed for
accuracy and resolution by selection of shorter gate times of the internal counter.
Table D-3
Table D-3
After one has optimized each individual measurement in terms of the minimum
time for the measurement with sufficient accuracy, there is yet another factor to
consider to improve test throughput: task allocation. This factor involves the
controlling computer and other instrumentation in the system. As stated in the
introduction to this product note, for the most part, the fastest instrument in the
test system is the dmm. Hence, its measurement rate may not be the throughput
bottleneck in the system. One can take advantage the high-speed measurement
Keysight 3458A User's Guide
shows the trade-off of resolution for each of the gate times.
Shows resolution trade off for each of the gate times.
Gate time
1 second
0.1 s
0.01 s
0.001 s
0.0001 s
Optimizing Throughout and Reading Rate
Resolution
7 1/2 digit
6 1/2
5 1/2
4 1/2
3 1/2
D
Read ing rate
1 rdgs/s
10 rdgs/s
73 rdgs/s
215 rdgs/s
270 rdgs/s
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