Simens Analog Output woes...

DanJack

Member
Join Date
Feb 2010
Location
Norway
Posts
16
I'm having a little issue with an analog output. I've setup the channels as a 4-20mA output in the hardware config, and I've checked that the physical selector switch on the side of the card is in the "2-wire" position. The channel is connected to a 2-wire current analog input on a Danfoss VLT Micro Drive Frequency Converter.

As I've understood it, if I write a value between 0 to 27648 to the PQW, I should be getting 4 to 20 mA on the output, i.e. 0 to 50 Hz. However, this doesnt happen. At value 0 i get approx. 10 Hz out and it reaches 50 Hz around 24200. Second of all, this result is not consistent. If I turn the PLC off and on again, the range changes so that i might end up with 14 Hz at value 0 but 50 Hz at value 21000.

I have no idea as to why the output behaves this way. Anyone come across anything like this? Could the output card be defective? (The PLC is 10 years btw, allthough it has almost never been in use).

-- DanJack
 
Value 0 and 10 Hz, how many mA's do you measure?
Same for 24200 and 50 Hz.
Same for 0 and 15 Hz.
Same for 21000 and 50 Hz.
 

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