Sensor driving a proportional valve

Hello all. I have a steam flow sensor that I am using to drive a proportional valve that is feeding steam into a mixer that will combine with process gases. I am using a 4-20mA signal in from the sensor, to drive a 4-20mA controlled proportional valve. The value for the sensor is coming from a carbon to steam ratio. Both of these analog modules are Omron NX's, which have 0-8000 count resolution. This proportional valve opens from 0° to 90°. I am not sure if I should use a 0-100% signal to the proportional valve, or if I should be using a the actual carbon to steam ration calculation, to drive it. Using a % for the valve doesn't sound very accurate to me, but I can't figure out another way to control it. Any advice would be great. Thank you.

are you saying that the output of the sensor is going to be connected DIRECTLY to the proportional valve? ...

I'll admit that I know NOTHING about your Omron gear - but my GUESS would be that you're going to need some type of control (maybe PID) between the input signal (from the sensor) and the output signal (to the valve) ...

I'm sure that some other forum members are going to know more about the type of process you're trying to control (since I know ZERO about the subject) - so be sure to get some other opinions - but personally I've never heard of a sensor signal feeding directly to a control valve ...

it's better,if this proportional valve provide feedback signal

Someone that know the process will have to tell you how to establish a flow setpoint for the steam. Then you could use PID, floating control, or deadband control to modulate the valve. This appears to be a simple feedback control system once the steam setpoint is determined.

Ron Beaufort said:

are you saying that the output of the sensor is going to be connected DIRECTLY to the proportional valve? ...

I'll admit that I know NOTHING about your Omron gear - but my GUESS would be that you're going to need some type of control (maybe PID) between the input signal (from the sensor) and the output signal (to the valve) ...

I'm sure that some other forum members are going to know more about the type of process you're trying to control (since I know ZERO about the subject) - so be sure to get some other opinions - but personally I've never heard of a sensor signal feeding directly to a control valve ...

Click to expand...

Thats what I asked the design engineer, "how is this sensor supposed to drive this PV?" He said it provided a signal, telling the PLC what % open the valve should be. Calling the mfg. they confirmed, the design engineer misunderstood what he was told. Yikes, I actually "spun my wheels in the mud" for a while on this. Thanks Ron

osmanjdt said:

it's better,if this proportional valve provide feedback signal

Click to expand...

Yes, thats what I told him. But, not my call.

Tom Jenkins said:

Someone that know the process will have to tell you how to establish a flow setpoint for the steam. Then you could use PID, floating control, or deadband control to modulate the valve. This appears to be a simple feedback control system once the steam setpoint is determined.

Click to expand...

I had to create a math function that calculates steam to carbon ratio. Of course it reads the flow sensor, then drives the PV.