Measuring Pulse Width - Fluke 289 User Manual

To measure duty cycle, position the rotary switch on one of the
functions allowing frequency measurements shown in Figure 23.
Press the softkey labeled Menu and move the menu selector to
the menu item labeled Hz,%,ms. Next press the softkey labeled
%.
8:10pm
123.45 VAC
49.75
0 100 200
59.756
Menu Save
Figure 26. Duty Cycle Display
As shown in Figure 26, the duty cycle percentage is shown in the
primary display while the signal frequency appears in the
secondary display. The mini-measurement display indicates the
06/13/07
%
Duty Cycle
Auto Range
300 400 500 VAC
Hz
Setup
est24.eps
volts or amps value of the input signal. The bar graph tracks the
volts or amps value of the signal and not the duty cycle value.
The pulse polarity is displayed to the right of the duty cycle value.
J indicates a positive pulse and K indicates a negative pulse.
To change the polarity being measured, press the softkey
labeled J K. The polarity indicator changes to the opposite
polarity.
For 5 V logic signals, use the 5 V dc range. For 12 V switching
signals in automobiles, use the 50 V dc range. For sine waves,
use the lowest ac or dc range that does not result in multiple
triggering. A manually-selected lower input range will often
measure better than the AUTO-selected input range.

Measuring Pulse Width

The pulse width function measures the amount of time a signal is
high or low, as shown in Figure 27. The measured waveform
must be periodic; its pattern must repeat at equal time intervals.
The meter measures pulse width from 0.025 ms to 1250.0 ms
ranges.
To measure pulse width, position the rotary switch to one of the
functions allowing frequency measurements shown in Figure 23.
Press the softkey labeled Menu and move the menu selector to
the menu item labeled Hz,%,ms. Next, press the softkey labeled
ms.
True-rms Digital Multimeters
Making Measurements
45