Hi folks,
I am using the NI9411 DI module on a cRIO 9074 to measure a 1 kHz PWM signal.
I created an empty project, set the mode of the module to "counter" "pulse width measurement" "High pulse" and "disabled" input filter.
For taking a first look at the measured values i used the NI distributed system manager.
At the beginning the measured values seem right, they are somehow multiplied with 10 but i can easily correct that with a normal division by ten.
The problem is, if i pull the plug which connects the NI9411 to the pwm generator, the duty cycle never goes to zero but stays somewhere between.
For example if the duty cycle is 510 (that is supposed to be 51) and i pull the plug it goes to 230 and stays there. If i repeat the step of plug-in and out, the duty cycle sometimes drops to 1.25 and sometimes to 70.
The values seem random and the counter stays at this value the whole time until i plug it back in.
For my application the module has to see the "missing" pwm if the plug is removed.
How can this be and how can i solve this problem?
Thanks