PaulKraemer
Electrical
- Jan 13, 2012
- 152
Hi,
I have a drive board (drive #1) that outputs a 4-20 mA signal that goes to a ABB signal converter, which converts the 4-20 mA to a 0-10 VDC signal that is used as a speed reference by another drive (drive #2). When I put my meter in series with the 4-20 mA circuit from drive #1 to the converter, I measure 4 mA when drive #1 is stopped (which is what I would expect). When I start drive #1 at a slow speed, I measure 5.25 mA. The fact that measured current increases from zero speed to a slow speed is also what I expect. What is causing me some confusion is that when I increase the drive #1 speed, my measured current stays at 5.25 mA, when I would expect that it would increase.
I have reason to believe that something is wrong with the converter. The reason I have this suspicion is because I removed power to the converter and removed all field wiring to it. I then measured the resistance between the terminals that the 4-20 mA signal goes to. This resistance measured 0.26 mA. I contacted ABB technical support and they informed me that this is a tell-tale sign the the converter is faulty and needs to be replaced.
I have no problem replacing the converter, but I would like to also (if possible) come up with a test that would prove whether the drive #1 4-20 mA output is working correctly.
I am wondering if I remove the converter from the circuit, would my meter (typical fluke digital multi-meter) alone be enough of a load to test whether the 4-20 mA output from drive #1 is behaving as it is supposed to? Or will I have to put some other load (to replace the converter) in the circuit?
I haven't mentioned the manufacturer/model number of drive #1 because I believe the 4-20 mA output is typical of what most drives and other automation components use to transfer analog values to other components. If it will be useful, I can certainly provide manufacturer and model numbers of all components.
Thanks and best regards,
Paul
I have a drive board (drive #1) that outputs a 4-20 mA signal that goes to a ABB signal converter, which converts the 4-20 mA to a 0-10 VDC signal that is used as a speed reference by another drive (drive #2). When I put my meter in series with the 4-20 mA circuit from drive #1 to the converter, I measure 4 mA when drive #1 is stopped (which is what I would expect). When I start drive #1 at a slow speed, I measure 5.25 mA. The fact that measured current increases from zero speed to a slow speed is also what I expect. What is causing me some confusion is that when I increase the drive #1 speed, my measured current stays at 5.25 mA, when I would expect that it would increase.
I have reason to believe that something is wrong with the converter. The reason I have this suspicion is because I removed power to the converter and removed all field wiring to it. I then measured the resistance between the terminals that the 4-20 mA signal goes to. This resistance measured 0.26 mA. I contacted ABB technical support and they informed me that this is a tell-tale sign the the converter is faulty and needs to be replaced.
I have no problem replacing the converter, but I would like to also (if possible) come up with a test that would prove whether the drive #1 4-20 mA output is working correctly.
I am wondering if I remove the converter from the circuit, would my meter (typical fluke digital multi-meter) alone be enough of a load to test whether the 4-20 mA output from drive #1 is behaving as it is supposed to? Or will I have to put some other load (to replace the converter) in the circuit?
I haven't mentioned the manufacturer/model number of drive #1 because I believe the 4-20 mA output is typical of what most drives and other automation components use to transfer analog values to other components. If it will be useful, I can certainly provide manufacturer and model numbers of all components.
Thanks and best regards,
Paul