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PWM Outputs


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Hey guys, 

I'm currently on a project using a US7-B5-TR22, one idea is to use the PWM output to command the frequency of an inverter. I know outputs needs to be enabled as a PWM output so I made a button to activate them when I use the inverter. The thing is that I don't have the inverter here to run some tests, and I wanted to see if the signals were as I wanted them to be.

I measured them with an oscilloscope to verify and I can see that the output has the correct frequency, but the signals are about 2mV and of course really noisy.

I'm wandering if I'm missing something here or if it's just normal ?

In the documentation it doesn't say anything about it.

Any idea ?

Thanks you guys.



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@DanT Hey, I've been checking as you said connecting a 3.3k resistor pull up to my V+ and the scope ground to CM4.

Results are that the signal is powered up but I have the 50Hz frequency...

I didn't put any load before the scope and I don't know yet the type of inverter that I will command.

Thanks for your quick answer.


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@DanT I found that the CM4 is not internally connected to the same supply network that the PLC, it's separated from the alimentation so I think the 50Hz emission comes from my scope which doesn't have a earth reference.

I was thinking about pulling up the HSO-0 with the 10V of the inverter and connect the CM4 to his 0V so I have the same reference but documentation advise me to not do it if I don't misunderstand...


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