M-7084 User Manual, Rev. A1.3 7PH-013-A13
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A.6 Frequency Measurement
Frequency is usually measured by one of the following two
methods.
1.
by counting number of signal pulses during a known time
interval, gate time
2.
by counting number of pulses of a reference clock during
the signal period
M-7084 uses the second method for the frequency
measurement. It counts number of pulses of the reference
clock during one signal period. The drawback of this method
is that the resolution will be small when the frequency is high.
M-7084 provides the high frequency measurement mode by
counting 11 signal periods, instead of only one period, to
increase resolution. The high frequency measurement mode
can be enabled by @AAFHVV command. Refer to Section
2.29 for details. The side effects of the high frequency
measurement mode are that it takes longer time and the
counting may overflow when the signal frequency is very low.
M-7084 can be set to automatic frequency measurement mode
by @AAFAVV command. Refer to Section 2.27 for details.
In automatic frequency measurement mode, the channel is
switched to the high frequency measurement mode when the
signal frequency is high and to the low frequency
measurement mode when the signal frequency is low
automatically.
