DWORD to REAL conversion

Hello,

I have been writing a program which reads values of reactive power from power analyser over Modbus RTU. Reactive power is represented by 32 bits while the MSb determine the sign. Program doesn't read the whole 32 bits instead of it reads two 16 bits words. After reading 32 bits I need to convert the value into REAL data type. So I wrote following conversion code in Structured text:

(structure stLovato_power contains in its items 16 bits words, which forms 32 bits representation of reactive power). It seems that reading is OK but something in the conversion is wrong. I still get 0 despite the values in iQ_HW and iQ_LW are nonzero. Can somebody tell me where I do a mistake? Thanks.

What PLC?

Hi steven,

Can you please share us the PLC brand and cat No.

Regards
Kannan K

It is PLC Beckhoff CP6202-0001-0000.

Use COP instrction and bit length 2 . it will convert 2x16 bit DINT data into 32 bit Real value. Or BIT shift register to read the whole RIO .

i can send u configuration file RSLOGIX5000.

Ping me on [email protected]

Thank you for your reaction kannanmkm. I am newbie in PLC programming and I have only some knowledge of structured text so
I would appreciate solution in ST.

Try this:

The result is unfortunately still zero.