analog io programming

how to program analog out put to give a certain % of motorised valve opening. temperature and humidity analog inputs are available .
This is for controlling the air that is fed to a paint booth.the system has a suction blower. humidity and temperature of atmospheric air (sucked by the suction blower )are measured(analog inputs). the air is chilled for moisture to condense. then it is heated to required temperature. The hot dry air is passed thru water curtain. humidity and temperature are measured at paint booth inlet. suitable correction is made in the opening of chiller valve/ burner valve and water spray to attain the desired humidity and temperature.
please advise how to program this.

sushami.joshi

It is impossible to answer your question unless you tell us what PLC you are using as all PLC's address analogue inputs and outputs differently.

Also, none of the regulars here will do your programming for you, they will advice you on what they consider to be the way to go.

You will find that you will get more replies if you post this question (with the PLC type) in the 'live questions and answers' forum.

Paul

What type of Analog output you talking about ? (0-10V) or (4-20mA) ?
What is the resolution ? (11 Bit/12 Bit/16 Bit) ? Find out the minimum and maximum number the Analog Register in the PLC can hold. e.g. (0-65,535) for 16 Bit Resolution.Once you get this info you can relate this number e.g. (0 - 65,535) with 0-100% opening of Motorised Valve and you can calculate how much counts you have to output to analog register to open the valve by 1%.In above example to open valve by 1% you will have to output 655.35 ~ 655 counts. so if you need 5% opening you will have to put 655*5 = 3275 count in the Analog register of the PLC.
This will work provided (0-10V) or (4-20MA) = (0-100%) opening of motorised valve.

You will have to write some rungs to make it happen.Hope this will help.

Are we comparing apples to oranges here?

My experience is in manufacturing (making things) rather than process control (making stuff), so maybe I'm not aware of all of the types of motorized valves available.

In my experience, an analog signal applied to a motor (usually via a drive) is either a velocity or an acceleration (torque) command. hey_rajan, what you're describing sounds more like control for a proportional valve than a motorized valve.

sushama.joshi, if your analog signal is a velocity command to the motor, you'll need to integrate the velocity over time to compute the amount of rotation of the valve actuator. Are you asking how to calculate the desired percentage of valve opening or how to open the valve once you've calculated the desired percentage?

Re: Are we comparing apples to oranges here?

Steve Bailey said:

manufacturing (making things) rather than process control (making stuff)

Click to expand...

That was hilarious !! Thanks for a Good Laugh after a hectic day !

input output module redundancy

I have another question. How do we achieve analog input and output module level redundancy. I am using PLC5 and flex I/Os.
also I have forgotten how did I got the screen for posting my question
in this forum (live Q&A). please help me with this too.
sushama