G'day,
Quick question regarding taking measurements on 4-20mA circuit.
We have a 24vdc control system on site controlled by PLCs. Most instruments feedback a 4-20mA analog signal to the PLC inputs. Now if I'm in the field taking a voltage measurement with a multimeter at the output terminals of a transmitter what reading should I expect? I would have expected to see between 1 and 5v. On some transmitters I do get a 1-5v reading but others I just see 24v.
If I break the circuit and place the leads in series I get the correct mA reading but donot always see the corresponding 1-5v when measuring across the output terminals.
The actual instrument in question is a Rosemount Flow tube/Transmitter. A number of these on site give me 1-5v across their outputs whereas another sees about 24v.
Cheers
Russ
Quick question regarding taking measurements on 4-20mA circuit.
We have a 24vdc control system on site controlled by PLCs. Most instruments feedback a 4-20mA analog signal to the PLC inputs. Now if I'm in the field taking a voltage measurement with a multimeter at the output terminals of a transmitter what reading should I expect? I would have expected to see between 1 and 5v. On some transmitters I do get a 1-5v reading but others I just see 24v.
If I break the circuit and place the leads in series I get the correct mA reading but donot always see the corresponding 1-5v when measuring across the output terminals.
The actual instrument in question is a Rosemount Flow tube/Transmitter. A number of these on site give me 1-5v across their outputs whereas another sees about 24v.
Cheers
Russ