Measuring Frequency Valve Duty Cycle

The measurement of frequency valve function is called its duty cycle, expressed as the percentage of time that the valve is open. It is measured by connecting a duty cycle meter, such as the Siemans 451, to a test connector. As an alternative, duty cycle can be measured with an ordinary dwell meter, such as the Sun TDT-11. The 90° scale of the dwell meter corresponds to the 100% scale of the duty cycle meter. For example, a duty cycle of 50% would be read as 45° on a dwell meter. The tests that follow express test values for both instruments.

To connect a duty cycle meter, attach the meter's positive and negative leads to the positive and negative battery terminals respectively. Connect the meter's signal lead to the duty cycle test connector.

To connect a dwell meter, attach the meter's positive lead to the duty cycles test connector. Connect the negative lead to ground. Set the meter to the four-cylinder scale.