Frequency Measurements - Fluke 87V MAX User Manual

Frequency Measurements

The Meter measures the frequency of a voltage or current
signal by counting the number of times the signal crosses
a threshold level each second.
Table 6 summarizes the trigger levels and applications for
measuring frequency using the various ranges of the
Meter's voltage and current functions.
To measure frequency, connect the Meter to the signal
source; then press
trigger slope between + and -, as indicated by the symbol
at the left side of the display (refer to Figure 9 under
"Duty Cycle"). Pressing
counter.
The Meter autoranges to one of five frequency ranges:
199.99 Hz, 1999.9 Hz, 19.999 kHz, 199.99 kHz, and
greater than 200 kHz. For frequencies below 10 Hz, the
display is updated at the frequency of the input. Below
0.5 Hz, the display may be unstable.
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 . Pressing  switches the
 stops and starts the
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How to Make Measurements
The following are some tips for measuring frequency:
• If a reading shows as 0 Hz or is unstable, the input
signal may be below or near the trigger level. You
can usually correct these problems by selecting a
lower range, which increases the sensitivity of the
Meter. In the  function, the lower ranges also have
lower trigger levels.
If a reading seems to be a multiple of what you expect,
the input signal may be distorted. Distortion can cause
multiple triggerings of the frequency counter. Selecting a
higher voltage range might solve this problem by
decreasing the sensitivity of the Meter. You can also try
selecting a dc range, which raises the trigger level. In
general, the lowest frequency displayed is the correct
one.
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