Analog Output Process Problem

hi all,
i'm using S7-300 first time,anybody have an idea how we process/programme the analog output.I m using it to control the vfd.

please advice if you can.

Use PID control block and unscale the PID output to have a
4-20mA output.

Hello hussain;

Many posts have discussed S7 analog ranges on this forum, here is one of them:

http://www.plctalk.net/qanda/showthread.php?t=31721&highlight=S7+analog+range

The values are shown for analog inputs but are also applicable to an anlog output module of the S7-300/400 family.

If your output module channel is configured (in HardwareConfig) for a current output of 0 to 20 mA and is wired properly, writing to the channel addess PQWxxx (a MOV instruction for example) the value dec(27648) will output 20 mA; a value of dec(0) will output 0 mA; a value of dec(13824) will output 10 mA (50%).

Or, as suggested by gherz817, use a function block to calculate or scale the value required. For example, use function FC106 "Unscale" located in the TI-S7 library to write the engineering value you want to output, and write it to the channel address.

Hope this helps,
Daniel Chartier

Thanks
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