Autoranging Time Base - Fluke CombiScope PM3370B User Manual

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3.8.4

Autoranging time base

The AUTO RANGE function of the Main Time Base (MTB) adjusts the time base
automatically, so that two to six waveform periods are displayed on the screen. If
a waveform doesn't contain enough information to calculate its period, the time
base is adjusted to acquire a minimum of two periods. One period of a signal is
determined by three successive crossings of the hysteresis band with the input
signal. The level of the hysteresis band can be set using the TRIGger:LEVel
command.
X1
HYSTERESIS
LIMITATION:
When operating with an acquisition length of 512 points, the maximum input
frequency is 25 MHz. For all other acquisition lengths, the maximum input
frequency is 50 MHz. When the input frequency is greater than the maximum alias
detection frequency, it is no longer possible to detect aliasing.
PROGRAM EXAMPLE:
CALL Send(0, 8, "INITiate:CONTinuous ON", 1)
CALL Send(0, 8, "TRIGger:SOURce INTernal1", 1)
CALL Send(0, 8, "SENSe:SWEep:TIME:AUTO ON", 1)
USING THE COMBISCOPE INSTRUMENTS
X3
X2
PERIOD LENGTH PERIOD LENGTH
Figure 3.16 Definition of a signal period
TRIGGER
LEVEL
ST7430
'Auto triggering
'Sets CH1 trigger source
'Sets auto time base on