Chroma 66203, User Manual

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Digital Power Meter 66203/66204 User’s Manual
4-12
4.5 Setting Measurement Range
There are auto and manual two measurement ranges for selection. The auto range is a
digital signal processor that selects the most appropriate range for measurement based on
the signal peak without processed by the digital filter. The manual range is set by the user
based on the actual test requirement and fixed to a certain range for testing.
When in auto range, the judgment condition for upper or lower range is different as the figure
shown below. When a signal peak exceeds the Up_Range_Limit of a certain range, it
means the signal needs to be measured in the higher range, and when the signal peak turns
to small, a lower range is required for measurement and Down_Range_Limit is used for
judgment. The gap between Up_Range_Limit and Down_Range_Limit is to measure the
dynamic signal or to avoid changing the range constantly when the signal is unstable and
cause low measurement speed or unable to measure effectively.
Compared with auto range the manual range is often used to reduce the range change time
during measurement. The user has to know the signal peak in the test process specifically
to select the proper range. Otherwise, the measurement will be incorrect if the signal peak
is much smaller than the range. When the signal peak is higher than the range limit, the
6203/66204 will prompt an over range (OVR or OCR) message. The OVR or OCR
message means the measured signal peak has been cut and could cause the measurement
incorrect. The 66203/66204 will not provide the measurement at this time.
Figure 4-17 Range Selection Rule
Under the 66203/66204 allowed rated power, to keep the protection mechanism from being
too sensitive, the OCR or OCP warning message will occur after confirmed the signal peak is
over the protection limit for 0.5 seconds. Even if the sound of operation is disabled, the
sound will not be turned off when the protection message is occurred.
No matter it is in AUTO range or Manual range, it would take some time to switch the range
as there will be transient for measurement circuit to switch the range. The transient will
cause the measurement data error and the DSP stops computing the data during range
change. The DSP will compute again when the transient is over.