4-2
IM WT5000-01EN
Crest Factor (Crest Factor)
The crest factor is defined as the ratio of the peak value of the waveform to the rms value.
Peak value
Rms value
Crest factor (CF) =
Peak value
Rms value
Input signal waveform
On this instrument, the crest factor is the ratio of the maximum applicable peak value to the measurement range.
Peak value that can be input
Measurement range
Crest factor (CF) =
You can set the crest factor to CF3, CF6, or CF6A.
• CF3: The crest factor is 3.
• CF6: The crest factor is 6.
• CF6A: The input range of the measurement range is expanded as follows as compared to when the crest
factor is set to 6. This is used to suppress frequent range changes when measuring a distorted waveform in
auto range mode.
• Condition for increasing the range in auto range mode
The voltage or current exceeds 220% of the currently set measurement range.
• Condition that cause an overload indication (“- - O L - -”) (for details, see section 1.3 in the Getting Started
Guide, IM WT5000-03EN)
The measured voltage or current exceeds 280% of the currently set measurement range.
The measurable crest factor is as follows:
{measurement range × CF setting (3 or 6)}
Measured value (rms value)
Crest factor (CF) =
* However, the peak value of the input signal must be less than or equal to the maximum allowable input.
If the crest factor of the input signal is greater than the specifications of this instrument (the crest factor defined
at the rated input), you can measure the signal by setting a greater measurement range. For example, even
if CF is set to 3, measurement is possible for signals with a crest factor greater than or equal to 5 when the
measured value (rms value) is less than 60% of the measurement range. If the minimum effective input (1% of
the measurement range) is being applied when CF is set to 3, measurement for CF = 300 is possible.
The voltage range, current range, effective input range, and measurement accuracy vary depending on the crest
factor setting. For details, see chapter 6 in the Getting Started Guide, IM WT5000−03EN.
• When you change the crest factor, the following settings change for all elements.
• All elements are automatically set to their maximum voltage and current ranges.
• In the valid measurement range settings, all measurement ranges are enabled (selected).
• If the crest factor is set to CF6 or CF6A, the measurement conditions of crest factor 5 and higher required
by IEC 62018 are met.
• When measuring waveforms whose crest factor is less than or equal to CF3, you can achieve more
accurate measurements by setting the crest factor to 3.
4 Input Settings (Advanced/Options)
