Hi,
I am installing a 4-20mA control loop using a Siemens Logo PLC driving a Kinetrol I/P actuator. I have used many of these pneumatic actuators over the years and I am familiar with its operation. This is the first time we are using the PLC setup to drive such an actuator. The actuator has been proven to work correctly and multiple have been tried with the Siemens PLC system.
When the PLC system was bench tested with only a fluke multimeter as the load we are capable of achieving 4-20mA.
When connected to the Kinetrol actuator the output will not drop below 5mA. We can achieve 20mA without issue. What can cause current to be "pulled up" in the way?
The Kinetrol actuator impedance is specified as 300 ohms. I have tested the PLC output with a resistor(s) making 570 ohms and I can achieve 4-20mA with no issues. On Monday I intend to increase this load until I can potentially replicate the issue.
So with a fluke with very low impedance and with a resistance greater than that specified for the actuator I can achieve the desired 4-20mA. This has a few of us confused and I am hoping an expert here may be able to point me in the right direction.
Thanks in advance.
Dan
I am installing a 4-20mA control loop using a Siemens Logo PLC driving a Kinetrol I/P actuator. I have used many of these pneumatic actuators over the years and I am familiar with its operation. This is the first time we are using the PLC setup to drive such an actuator. The actuator has been proven to work correctly and multiple have been tried with the Siemens PLC system.
When the PLC system was bench tested with only a fluke multimeter as the load we are capable of achieving 4-20mA.
When connected to the Kinetrol actuator the output will not drop below 5mA. We can achieve 20mA without issue. What can cause current to be "pulled up" in the way?
The Kinetrol actuator impedance is specified as 300 ohms. I have tested the PLC output with a resistor(s) making 570 ohms and I can achieve 4-20mA with no issues. On Monday I intend to increase this load until I can potentially replicate the issue.
So with a fluke with very low impedance and with a resistance greater than that specified for the actuator I can achieve the desired 4-20mA. This has a few of us confused and I am hoping an expert here may be able to point me in the right direction.
Thanks in advance.
Dan
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