Keysight Technologies 3458A Guide D'utilisation page 175

Math Operations
Each math operation performs a specific mathematical operation on each reading
and/or stores data on a series of readings. The multimeter can perform the null,
scale, percent, dB, dBm, filter, RMS, or temperature-related math operations on
readings. The statistics and pass/fail math operations do not alter readings but
store information pertaining to readings. This section describes how to enable and
disable math operations and discusses each math operation in detail.
Real-time vs. post-process
Math operations can be performed real-time or post-process. When a real-time
math operation is enabled, the operation is performed on each reading
immediately after the reading is taken. The result can then be stored in reading
memory or output over the GPIB. When enabled, a post-process math operation
(except STAT and PFAIL) is performed on each reading as it is removed or copied
from reading memory to the display or the GPIB output buffer. (The readings in
memory are not altered by any post-process math operation.) The STAT or PFAIL
post-process math operations are performed using the readings in memory
immediately after executing the MMATH command. For the statistics operation,
results are stored in the statistics registers. For the pass/fail operation, an out of
limit reading sets bit number 1 in the status register and displays either FAILED
HIGH or FAILED LOW depending on whether the high or low limit was exceeded.
Enabling math operations
To enable a math operation, send the MATH command (for real-time) or the
MMATH command (for post-process) followed by the operation parameter (DB,
DBM, FILTER, NULL, PERC, PFAIL, RMS, SCALE, STAT, or one of the
temperature-related parameters; refer to "Measuring Temperature, later in this
section for a listing of the temperature-related parameters). After enabling a math
operation, it remains enabled until you disable it, cycle power, execute RESET, or
execute one of the PRESET commands. For example, to enable the NULL
operation, send:
OUTPUT 722; "MATH NULL" !ENABLES REAL-TIME NULL OPERATION
or
OUTPUT 722; "MMATH NULL" !ENABLES POST-PROCESS NULL OPERATION
Keysight 3458A User's Guide
Making Measurements 4
175