Hello Everyone,

I am working on Safety PLC CPU 1510 SPF-1 PN.

While testing DO module 6ES7 136-6DB00-0CA0, I have come up with below issue.

When DO is not on, I am getting -20.12VDC in DQ-P0 and DQ-M0.

When I give ON command, I am getting 24VDC(which is okay). 

Why is it giving negative voltage when there is no command? 

Am I doing wrong wiring or some setting is not correct in PLC hardware configuration?

Please help.

Regards,

Shailesh Bangale

I have attached image of Hardware configuration. 

Do I need to select "Activated light test"?

One thing I did not mention, I did not connect earth here. But the problem I got only for DO module. Rest of the DI and AI module are working fine.

What fault I am doing here? Or something I am missing?

I got solution.

I think it basics of electronics and requirement of F-DO module.

I must connect a load at each output channel. When I connected a load i.e. Relay coil, I got 0VDC on channel.

I did not do any modification in software FYI. 

That's relief now. Everything is working and I got know the reason.

Thanks.