AB 753 4-20ma

[ptonsparky]

Simple question. What is the proper connection for a 4-20 ma transducer on a AB 753 VFD? (The one that works of course...). Ordered one already set up with disc in a Hoffman enclosure and all the goodies. Door mounted pot 0-10v worked great. Schematic for field installed 4-20 was not a winner. I had start on site start up support from the local wholesaler plus AB phone support. No answers yet. They took one of my Prosense pressure tranducers back with them to bench test it but we have had no problems at all with them on previous jobs.

 

[GoldDigger]

Simple question. What is the proper connection for a 4-20 ma transducer on a AB 753 VFD? (The one that works of course...). Ordered one already set up with disc in a Hoffman enclosure and all the goodies. Door mounted pot 0-10v worked great. Schematic for field installed 4-20 was not a winner. I had start on site start up support from the local wholesaler plus AB phone support. No answers yet. They took one of my Prosense pressure tranducers back with them to bench test it but we have had no problems at all with them on previous jobs.

Simple question back: Have you measured the loop resistance to the remote transducer? If that was too high there would be problems. Also the supply voltage to the transducer?

Neither one may be your problem, but I want to make sure those have been considered.

Have you measured current and voltages when you try to use the remote? I am guessing that you are expecting the AB to supply the loop power. That may be the thing that needs to be configured.

 

[ptonsparky]

Simple question back: Have you measured the loop resistance to the remote transducer? If that was too high there would be problems. Also the supply voltage to the transducer?

Neither one may be your problem, but I want to make sure those have been considered.

Have you measured current and voltages when you try to use the remote? I am guessing that you are expecting the AB to supply the loop power. That may be the thing that needs to be configured.

Loop to transducer is 20' maybe. It is good. Yes we are expecting the power loop to come from AB. We are leaving something out. Could be as simple as a jumper between commons but at over $15000 I tend not to experiment . No current flow in loop.

 

[petersonra]

Is this a 2 wire xmtr?

There is a terminal on the drive that supplies +24V that would go out to the xmtr and the return wire from the xmtr would go to the + terminal on the AI. You have to jump the AI- to 24V common at the drive end.

Doing this from memory so you might want to look at the manual.

you also have to set up the parameters to configure the AI.

The manual is a little confusing as it shows the 4-20mA signal coming in directly to the AI + and - terminals but that only works if it is a 4 wire xmtr.

 

[ptonsparky]

Is this a 2 wire xmtr?

There is a terminal on the drive that supplies +24V that would go out to the xmtr and the return wire from the xmtr would go to the + terminal on the AI. You have to jump the AI- to 24V common at the drive end.

Doing this from memory so you might want to look at the manual.

you also have to set up the parameters to configure the AI.

The manual is a little confusing as it shows the 4-20mA signal coming in directly to the AI + and - terminals but that only works if it is a 4 wire xmtr.

I think that is the problem exactly.

thanks.