analog configuration and program

I am wanting to use the 0-100 output data from a PID instruction to send out a 4-20mA signal from an analog ouput card to a Phase Angle controlled Solid State Relay. This is to control a heater. Using Logix 5000 L5563. I would like to know if I can just write a compute instruction to convert the 0-100 to a 4-20 and then write it to the analog out or is there a different way to do it. I know the analog cards are set up for either 0-10VDC or 0-20mA.

Use scale instruction, PID output is the input for the scale instruction, min value of output is 4000, max value is 20000, then configure your analog module output as engineering values (ie. 4000 - 20000)

If I remember correctly, there is no scale instruction in 5000. I think it would have to be a compute

There is a scale function block if you have access to FB or there is an AOI for SCP.

Hope this helps.

if you'll post the exact numbers that you want to use, then someone will probably post the exact CPT formula to perform the calculation ...

we need to know the "FROM" range (minimum and maximum) and the "TO" range (minimum and maximum) ...

If you are using a 1756 analog output module there is no need for an external scale instruction. Just set up the module channel you're using for 4mA = 0 and 20mA = 100. Then tie the PID instruction output directly to the analog output address.

danny.michael said:

If you are using a 1756 analog output module there is no need for an external scale instruction. Just set up the module channel you're using for 4mA = 0 and 20mA = 100. Then tie the PID instruction output directly to the analog output address.

Click to expand...

Also, make sure select Float Data for the Comm Format to maintain the best resolution.

Stu....