Fluke 289 - Manual (Page 26)

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Users Manual
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out open lead conditions so the Meter leads can be moved
between test points without triggering a display update.
Note
For temperature measurements, the AutoHold
threshold is a percent of 100 degrees. The default
AutoHold threshold is 4% of 100 degrees, or 4 degrees
Celsius or Fahrenheit.
Pressing H while in AutoHold mode, forces the Meter’s
display to update with the present measurement, just as if a
stable measurement had been detected.
To set the AutoHOLD Threshold Value, press the softkey labeled
Setup to access the setup menu. Using the cursor buttons, move
the menu selector next to the menu item labeled Recording and
press the softkey labeled Recording to open the recording setup
screen. Using the cursor buttons, move the menu selector next
to the menu item labeled Event Threshold for AutoHOLD and
then press the softkey labeled Edit. Press 7 or 8 to scroll
through the AutoHold threshold values. With the desired value
selected, press the softkey labeled Close.
Measuring Crest Factor
Crest factor is a measure of signal distortion and is calculated as
a signal’s peak value over its rms value. This is an important
measurement when looking at power quality issues.
The Meter’s crest factor function is only available for the ac
measurements: Vac, mVac, Aac, mAac, and
μ Aac. With the
Meter in one of the ac measurement functions, press the softkey
labeled Menu. Next, move the menu selector next to the menu
item labeled Peak,CF and press the softkey labeled CF. The
crest factor value is displayed in the primary display while the ac
measurement appears in the secondary display. Frequency, duty
cycle, and pulse width are not allowed during crest factor
measurements.
Capturing Minimum and Maximum
Values
The MIN MAX Record mode captures minimum, average, and
maximum input values. When the input goes below the recorded
minimum value or above the recorded maximum value, the Meter
beeps and records the new value. The Meter stores the elapsed
time since the recording session was started at the same time.
The MIN MAX mode also calculates an average of all readings
taken since the MIN MAX mode was activated.
This mode is for capturing intermittent readings, recording
minimum and maximum readings unattended, or recording
readings while equipment operation precludes watching the
Meter. The MIN MAX mode is best for recording power supply
surges, inrush currents, and finding intermittent failures.
Response time is the length of time an input must stay at a new
value to be captured as a possible new minimum or maximum
value. The Meter has a 100 millisecond MIN MAX response time.
For example, a surge lasting 100 milliseconds would be captured
but one lasting only 50 milliseconds may not be captured at its
actual peak value. See the MIN MAX specification for more
information.
The true average value displayed is the arithmetic mean of all
readings taken since the start of recording (overloads are
discarded). The average reading is useful for smoothing out
unstable inputs, calculating power consumption, or estimating
the percentage of time a circuit is active.