I am sending a 4-20mA signal from an Allen Bradley 1769-OF4 card to a variable frequency drive(VFD).
I set the card output to 20mA and verified a 20mA signal at the end of the signal wires, prior to termination at the VFD.
However, when the signal wires are terminated to the VFD, the 20mA signal degrades to about 12mA (half scale).
I sent a 20mA signal to the VFD from my process meter, with the signal wires disconnected, and all was well.
I don't think current is affected by impedence. Allen Bradley states the signal should be good if the resistance is less than 600ohms.
Does anyone know what would cause the signal degadation and/or what I can do to resolve the issue?
I don't have any info on the VFD yet.
Thanks,
I set the card output to 20mA and verified a 20mA signal at the end of the signal wires, prior to termination at the VFD.
However, when the signal wires are terminated to the VFD, the 20mA signal degrades to about 12mA (half scale).
I sent a 20mA signal to the VFD from my process meter, with the signal wires disconnected, and all was well.
I don't think current is affected by impedence. Allen Bradley states the signal should be good if the resistance is less than 600ohms.
Does anyone know what would cause the signal degadation and/or what I can do to resolve the issue?
I don't have any info on the VFD yet.
Thanks,