slc had the SPC function...

[briana banks]

Hi

Why it doesnt included in the plc-5 software RSlogix 5?

thanks.

 

[504bloke]

Do you mean SCP in Logix 500 ?

 

[briana banks]

yes.
there is no such instruction in rslogix 5
thanks

 

[rdrast]

Probably because the SLC's are newer, and the PLC's also had the ability to do scaling right at the analog modules.

Creating a 'y=mx+b' scaling subroutine isn't that difficult, and has been brought up here many times.

 

[Ken Moore]

use the compute instruction CPT. Standard 1771 analog cards are 12 bit, so your raw counts will be 0-4095.

Divide current counts by max counts, this wil give you percent of scale, then multiply that by the span of your engineering units, then add any offset from zero.

Here's an example using engineering scale of 50-300, assume current counts are 2047.

((2047/4095)*250))+50=scaled results of 174.97(stored in a floating point register)