IO-AI4AO2 problem

[vamalgise]

Hello,

I operate 3 way control valve with 0...10V signal with analog output of IO-AI4AO2.

I linearize 0...100% signal from PID out to 0...4095 bit to analog output.

When PID signal is 0 and output is 0, i measure voltage in AO0 of IO-AI4AO2 and there is 9,3 V, when i give 100% signal, there is 14,4V on the output.

Obviously valve does not operate properly. 

One more curious thing is that when PID out signal is more than 0, fault LEDs on the module start blinking ( AO short circuit and AI out of range) with specific frequency, like once in 5 seconds lets say analog input 0 goes to high limit value.

What could be the problem? Could it be some noise?

Thank you in advance guys.

[AlexUT]

Hi vamalgise,

0-20 and 4-20 mA Analog Outputs require maximum load impedance not more than 500 oHm.

If valve you use require some minimal fixed voltage to work, or have dynamic resistance, you have to use current loop repeater to fix this problem.

B.R.

 

[Ausman]

Hi Vamalgise,

If it's a good brand of valve, it should work ok straight away.

I'd also re-check the following:

1).  The wiring is into the correct terminals on the  AI4AO2. It is very easy to go in the wrong hole!  Expecially in an awkward location.

2). You haven't got the input and output lines from the actuator/modulator on the valve mixed up?

3). Everything within your program, and hardware setup is matched to using 0-10V?

cheers,

Aus