Hi,

I have a Simatic-555 controller and an Woodhead Applicom to communicate to the controller through OPC client.

I want to control the analog output (4-20ma), memory address WY1994 by writing a value through the OPC client, it sends the value to the controller however, it won't hold the value for long (in just a split of a second), then it will return back to 4ma.

Through the OPC client, I see a Vf address and I think this is the address that will hold the value for WY, however, I do not know how to relate the WY1994 address to Vf* address... I want to force the wy1994 to 15 ma...

Thanks.

 

A WY address is part of the image register and there is no other way to address the WY The Vf you mention seems like a Floating point (32 bit) V memory address.

If you write to a WY in a SIMATIC 555 PLC then you must know that this is a WORD address
0 = 0mA, 32000 = 20 mA, so 4 mA = 6400

Probably there is PLC code writing to the WY as well. Use cross reference to locate where.

You can write to an available V (f) memory location, consisting of 32 bits = 2 words V memory.

Then you must write PLC code to "UNSCALE" the V(f) memory to a WY.

You will find an UNSCALE function in the SIMATIC 555 its Special Functions (sort of Pascal programs you can create and call, they execute cyclically or on event).

Ronald