196
Measurement Speed and Accuracy Trade-offs
General Guidelines for Increasing Measurement Speed
The following guidelines show how to increase measurement speed, which
in some cases, will reduce the accuracy of the measurement. Some of the
guidelines will not affect accuracy but simply make taking measurements
more efficient. Be aware that these guidelines also increase the complexity
of the program.
1. Avoid function changes.
2. Avoid aperture changes when making frequency or period
measurements.
3. Minimize the number of command/response sessions.
4. Set autozero to
ONCE
or
OFF
.
5. Turn autorange
OFF
.
6. Decrease the NPLC setting for DCV, DCI, 2-wire and 4-wire
resistance measurements.
7. Store the readings in the E1412A internal memory instead of sending
them directly to the computer.
Note
Only items 4, 5 and 6 may reduce the accuracy of a measurement. The rest
of the guidelines involve additional work by the system programmers.
Avoid Function
Changes
The E1412A Multimeter takes time to switch between the various functions
because the hardware must be re-configured for the new function. Organize
your program so all measurements on a function are done at the same time.
Avoid Aperture
Changes
Changing aperture times for frequency or period measurements takes a
significant amount of time. The easiest way to avoid aperture changes is to
directly specify the aperture time. This requires that you not use the
MEASure
command and that you not specify the optional <
resolution
>
parameter in a
CONFigure
command.
Minimize the
Number of
Command/
Response Sessions
Minimizing the number of command/response sessions involves
programming the multimeter to pace itself, rather than the computer pacing
the multimeter. Use the external trigger mode when measuring signals
routed to the multimeter from a switch module.
The
EXTernal TRIGger
input can be used to start a scan from an external
signal. The E1406 Command Module “Clk out” is a convenient source for
an external signal. A potential problem exists whereby an external trigger
arrives before the multimeter is ready to start a new scan causing the trigger
to be missed and no error message generated. Send a
*OPC?
command to the
multimeter after setting up the multimeter and prior to initiating the switch
module to eliminate this problem.
Set Autozero to
ONCE or OFF
Autozero causes the A/D to alternately measure its internal zero and the
external signal. Autozero improves reading accuracy; however, it reduces
reading speed by ½.
Summary of Contents for Agilent E1412A
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Page 10: ...8 Contents Notes...
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Page 26: ...24 Agilent E1412A Multimeter Module Setup Chapter 1 Notes...
Page 194: ...192 Agilent E1412A Multimeter Error Messages Appendix B Notes...
Page 201: ...Index 199 Index Agilent E1412A User s Manual and SCPI Programming Guide...
