Making relative measurements – Fluke 289 User Manual

Page 31

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True-rms Digital Multimeters

Making Relative Measurements

21

Making Relative Measurements

The Meter displays calculated values that are based on a stored
value when set to relative and relative percent mode. Figure 9
shows the functions for which the two relative modes are
available. In addition, the two relative modes are available in
frequency, duty cycle, pulse width, crest factor, and dB.

est29.eps

Figure 9. Relative Mode Functions

To activate the relative or relative percent modes while in one of
the functions shown in Figure 9, press the softkey labeled Menu.
Move the menu selector to the menu item labeled REL. Next,
press either the softkey labeled REL or REL%. The
measurement value at the time that either Rel or Rel % is
enabled, is stored as the reference value and displayed in the

secondary display. The present or “Live” measurement moves to
the secondary display and the primary display indicates the
difference between the present measurement and the reference
value in measurement units for REL and as a percentage for
REL %.

When relative percent is enabled, the bar graph is a zero-
centered bar graph that indicates the percentage difference. The
bar graph’s range is limited to

±

10 %, but the display goes to

±

999.9 %. At 1000 % or more, the display indicates OL. When

the reference value is 0, the Meter displays OL.

With the exception of dB measurements, ranging is set to
manual and can not be changed. Both auto and manual ranging
is possible when making relative dB measurements.

When relative is enabled during dBm or dBV measurements, the
displayed units change to dB.

In relative or relative percent mode, the softkey label for F3
indicates REL or REL%, depending on which of the two modes
is not presently selected. The F3 button acts as a toggle,
switching the Meter between the two modes. Moving the rotary
switch between V and mV while in relative dBm or dBv mode
does not disable the dB measurement. This allows continuous
measurements over a wide range of input voltage.

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