ddeshi2
Member
Hello everyone,
We have a backpressure valve with digital positioner (two-wire) connected to an analog output card ( Automation Direct). This valve has to control the pressure by opening or closing depending on the pressure transducer value connected to analog input module. Everything worked fine until last week when all of a sudden the valve started behaving erratic. We opened the valve and checked for any mechanical faults, but everything looked fine. We checked the digital positioner and changed it to a new one because we found some moisture on the old positioner circuit board. After changing the positioner the valve has stopped responding( neither opening/closing) to the PLC signal. The positioner has an option to set either in auto/manual mode and I'm able to open and close the valve by placing the positioner in manual mode but not from HMI. When the positioner was placed in manual mode I checked the mA signal by connecting multimeter in series and found that at 0% it was 4 mA. I slowly increased the valve opening but the multimeter value didn't change ( showing 4 mA at 100%). What does this mean? Does it mean the positioner needs 4-20 mA calibration? or is it something else?I'm new to this field and appreciate your help in figuring out the problem .
Thanks,
Andy
We have a backpressure valve with digital positioner (two-wire) connected to an analog output card ( Automation Direct). This valve has to control the pressure by opening or closing depending on the pressure transducer value connected to analog input module. Everything worked fine until last week when all of a sudden the valve started behaving erratic. We opened the valve and checked for any mechanical faults, but everything looked fine. We checked the digital positioner and changed it to a new one because we found some moisture on the old positioner circuit board. After changing the positioner the valve has stopped responding( neither opening/closing) to the PLC signal. The positioner has an option to set either in auto/manual mode and I'm able to open and close the valve by placing the positioner in manual mode but not from HMI. When the positioner was placed in manual mode I checked the mA signal by connecting multimeter in series and found that at 0% it was 4 mA. I slowly increased the valve opening but the multimeter value didn't change ( showing 4 mA at 100%). What does this mean? Does it mean the positioner needs 4-20 mA calibration? or is it something else?I'm new to this field and appreciate your help in figuring out the problem .
Thanks,
Andy