hi

I have created scaling function like fc105 ,here is my programming,please help me if i had wrong in programming.

thx

Hello Hamed,

There is an issue with the <bipolar> part.

The analog value needs to be normalized between 0.0 and 1.0. Consider that the bipolar analog gives a value between -27648 and 27648.

The formula    x = MD14 / (27648 + 27648)    will not have the wanted result.

MD14 ==  -27648.0      x =\= 0.0 .. problem!
MD14 ==  +27648.0     x =\= 1.0 .. problem!

I will leave you to think about this problem. Also consider what you are doing when the analog input is 4-20mA on a channel that handles 0-20mA. The same type problem for 1-5V on a 0-5V channel.

As for the RETURN part: If I remember correctly the 'return' parameter is somewhere with the rest of the parameters. It needs to be set to something else than 'void'; like 'real'. Then the name of that parameter is the same as the name of the FC. Use it as-if it is an out parameter.

BR

i will think and solve the problem that u mentioned

thank u

hello #dp

here is my correction to the above program ,as you have mentioned there was wrong part in my program with bipolar signals scale,the only modification that i have made  with bipolar adding 27648 to the value from analog input card then dividing the result by two times of 27648 ,multiplying with span,finally adding with low limit value

(value+27648)/(2*27648)+low limit value

but about 4-20ma signal which we wanna measure in 0-20ma channel i think we can consider it is 0-16 ma and scaling it then add with low limit  value,am i right?

Hello.

hamed12580

hello #dp

here is my correction to the above program ,as you have mentioned there was wrong part in my program with bipolar signals scale,the only modification that i have made  with bipolar adding 27648 to the value from analog input card then dividing the result by two times of 27648 ,multiplying with span,finally adding with low limit value

(value+27648)/(2*27648)+low limit value

but about 4-20ma signal which we wanna measure in 0-20ma channel i think we can consider it is 0-16 ma and scaling it then add with low limit  value,am i right?

That function receives upper + lower limits, as well as bipolar (false / true) selection. Those datas are overlapping in purpose. Receiving upper + lower limits gives the ability to solve a general problem and the bipolar selection is not required.

Please review a very old S7-200 FAQ attached as a zip file. Inside the file file is the original HTML file with auxiliary folder. Compare the idea presented within, with your ideas.

EDIT .. LAD code for the S7-200 is now included in the zip archive. Warning: the hard limits are not the same as the PLC you are working with.

BR