Making Measurements 2U1461A/U1453A User’s Guide 81Measuring duty cycle and pulse widthYou must first enable the duty cycle and pulse width display in the Setup menu.See “Enabling the (+ or –) duty cycle and pulse width display” on page 157 formore information.While displaying voltage or current frequency, press to select themeasurement as a percentage (%) for duty cycle or in the millisecond (ms) unit forpulse width.NOTE – The duty cycle (or duty factor) of a repetitive pulse train is the ratio of thepositive or negative pulse width to the period expressed as a percentage. Theduty-cycle function is optimized for measuring the on or off time of logic andswitching signals. Systems such as electronic fuel injection systems andswitching power supplies are controlled by pulses of varying wid th, whichcan be checked by measuring the duty cycle.– The pulse width function measures the amount of time a signal is high or low.It is the time from the middle threshold of the rising edge to the middlethreshold of the next falling edge. The measured waveform must be periodic;its pattern must repeat at equal time intervals.– The bar graph does not indicate duty cycle or pulse width value but indicatesthe voltage or ampere value of the input signal.– The duty cycle polarity is displayed to the left of the duty cycle value.indicates a positive pulse width and indicates a negative pulse width.Change the polarity in the Setup (see page 157).
