Frequency And Period; Optimizing The Testing Process Through Task Allocation; Math Operations; Data Storage - Agilent Technologies 3458A User Manual

Frequency and
Period

Optimizing the Testing Process Through Task Allocation

Math Operations

Data Storage

330 Appendix D Optimizing Throughout and Reading Rate
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 32 shows the trade-off of resolution for each of the gate times.
Table 32: 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
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
capability of the 3458A by letting it compute its own statistics, linearize its own
thermistors, or check its own limits while the controller is controlling other
instrumentation or is otherwise busy. The features of the 3458A dmm that make
this possible are the built-in math functions, the Reading Memory, State Memory
and Program Memory.
The time necessary to transfer measurements and commands to the computer is
computer dependent. GPIB turnaround time, the time to process OUTPUT and
ENTER operations will vary considerably from computer to computer. The
features of Program Memory, Reading Memory, State Storage, and
post-processing math operations all tend to decrease GPIB overhead and make
the testing time far less computer dependent.
Individually, math operations performed within the 3458A slow the measurement
speed of the 3458A, but many times the combination of the 3458A with the
controller will perform faster together to achieve final answers if the 3458A does
some of the math itself. This is particularly true for pass/fail limit checking where
The computer is alerted only if the test has failed. If statistics are important on the
measurements, then it is a simple matter to let the 3458A assume the task of
computation instead of having to write a program on the controller. The computer
in the 3458A is a very powerful Motorola 68000 with a 8 MHz operating clock;
therefore, many times it will have the same computational power that the
controller has.
The memory of the 3458A can be used to store measurements for later transfer to
the controller for up to 10,000 readings (20 kBytes). Optionally, one may use the
Option 001, Expanded Memory and get an additional 65,000 reading (128 kBytes)
Resolution Reading Rate
7 1/2 digit 1 rdgs/s
6 1/2 10 rdgs/s
5 1/2 73 rdgs/s
4 1/2 215 rdgs/s
3 1/2 270 rdgs/s