PineMarten,
Is there a signal conditioning, or load range resistor (ex. 250 ohm) installed as part of this loop? If so, the actual input needs to be set for 1-5 volts.
When you say the recorder reads 7-9 mA, are you actually deriving these values from a different set of displayed engineering units, or do you have the recorder actually set up for mA display?
It sound like, as Matt suggests, that a signal generator, or loop calibrator would quickly rule out the possibility of a faulty transducer, or input channel.
They could be purchased from Omega and received fairly quickly. They are invaluable for process loop instrumentation servicing.
Also, I'm not convinced that adding the indicator, while increasing loop resistance, would necessarily lower the loop current. I believe this type of transmitter is a constant current transmitter, and automatically compensates for additional loop devices to a certain extent.
Matt,
On a 4-20 mA loop, at 1/2 process span, the loop should read 12 mA. which is the 8 you mention plus the 4 from which zero begins.
[This message has been edited by Redsy (edited 08-26-2003).]
