SCP and PID Issue

[rodrider]

I know a lot has been covered here regarding this issues but yet i still get lost. i am using these analogue cards
1. 1746-NI8 configured for 4-20ma
2. 1746-NO4 output 4-20ma

my issue is what values to use for scaling i have seen so many different values in the input min, input max, scale min, scale max,
i connected a 0 to 30psi hart transmitter 4 to 20 ma to the analogue input module. i want to vary the pressure to the transmitter using a regulator to control a valve using a i/p converter, i should monitor the output of the i/p with a guage for a 3 to 15psi output.
i have attached what i have done please help thanks

 

[Ron Beaufort]

welcome to the forum ...

first of all, please give us some more detail about the following ...

i want to vary the pressure to the transmitter using a regulator

something just doesn't sound right about that ... is this a student exercise – or a real-world project? ... we'll help either way – but it helps to know what we're dealing with ... the more you tell us about the entire system, the more we can help ...

going further ...

to get more detailed answers, you need to post your entire RSS project file – not just a screen shot of a few rungs ... much of what we need to know for a system like this will be included in the module configuration (etc.) which isn't available in the rungs ... (note that you'll have to zip the RSS file before posting it – forum rule) ...

.

 

[SilverShotBee]

Ron,

Why would it need to be 0 instead of 3277? 3277 would be 4mA on a 0-20mA scale wouldn't it?

 

[Ron Beaufort]

N10:29 is entered as the CV of your PID instruction ...

in RSLogix500 systems, the CV (output) value ALWAYS ranges from 0 to 16383 ... since the Input to your SCP is the output of the PID, then your scaling needs to reflect that "native/raw" range of values ...

 

[rodrider]

i have attached the file.
this is a learning stuff, i have done a lot of discrete logic exercise am just stepping into analogue.

what i intend to do here is use a air regulator fisher to vary the input pressure to the transmitter, say at 0psi the output of my i/p should read 3psi on a gauge and the valve attached to it should be in closed position and at 30psi, the i/p should read 15psi on the gauge and the valve should be fully open, or to control a valve from 0 to 100%
thanks

 

[SilverShotBee]

N10:29 is entered as the CV of your PID instruction ...

in RSLogix500 systems, the CV (output) value ALWAYS ranges from 0 to 16383 ... since the Input to your SCP is the output of the PID, then your scaling needs to reflect that "native/raw" range of values ...

I didn't know that, always good to pick something up like that!

 

[Ron Beaufort]

always good to pick something up like that!

that's why we're ALL here ...