Loop powered device and NI 9265

[Gearmiester]

I have been working with a cRIO 9023 with a 9114 chassis that includes the FPGA. On the chassis I have a NI 9265 4 chan 0-20mA output module. On the test bench I have wired in a Laureate Series 2 panel meter set up for mA with a Dale RH-5 5 watt 7.5 ohm resistor between AO0 and Com to simulate load (so the meter will read output.) This set up works fine and I can read output from the 9265 that varies with the LabVIEW program control.

In the field I am using this signal to drive a Parker 24v 4-20mA pump driver card (pn 027-22063-0) The 24vdc power is being passed through a signal conditioner coming from the 24vdc batterys for the engine. the signal conditioner acts as an isolator for the ground to prevent ground loops from the other systems. The 4-20 mA signal is being supplied by the NI 9265 (the pump driver requires two different circuits one for 24vdc and one for 4-20mA) However, the issue is that the pump driver card does not recognize the 4-20mA signal from the 9265 as a loop so the pump driver does not work.

I have tested the pump driver card with a Dwyer ASG 0-20mA signal generator and external power supply (set up the same way that it is in the field) and the pump driver works, so I am at a loss as to what the difference is between the Dwyer generator and the 9265 card.

So my question is do I need a diode from AO0 to Com in order to have the driver card recognize the loop? Is that adviseable (I have not done this yet) or is there some other way for the 4-20mA signal coming from the 9265 to be recognised as a loop by the driver card?

To be sure I have checked all wiring from the cRIO 9265 unit to the pump drive in the field and there are no breaks or issues. I did this by pulling the wires off the 9265 and connected them to the Dwyer ASG and the pump card worked. I can post the test program from Labview but it works fine as I am getting output mA in the test lab.

As of now I have a driver card on one channel and a 5watt resistor to laurel meter on another channel in the test lab. I can see the output on the meter when i run the program but still not on the driver card.

thanks

[AlexAlligator]

Hello Gearmiester,

I can't give you a definite answer concerning the diode placement at this time, but I will take a look at the device specifications and see if I notice any differences between the NI 9265 and the Dwyer ASG. Are we talking about a rectifier circuit in regards to the diode?

What does your LabVIEW code concerning the NI 9265 look like? How is the Analog Output being generated in software?

[Gearmiester]

Here are the VI's for the test program. As far as the rectifier circuit i would say; no, in as much as I am not trying to convert AC to DC because the  output of the 9265 card is the same voltage characteristic as the supply input which is DC. It's the mA loop that is not being recongnized. And I am not trying to convert the 0-20mA loop to 0-5v or 0-10v.

[AlexAlligator]

Hello Gearmiester,

I apologize for the long time you've been waiting for a reply. Is the NI 9265's current loop still not being seen by the Parker pump driver card? Has the current monitoring diode being added to the circuit enabled the 9265 current loop to be seen by the pump driver?

Is the 9265 device powered and connected to the circuit similar to the following document?

http://zone.ni.com/reference/en-XX/help/371361G-01/lvmeasapps/measuring_current/

It seems like there may be an break in the current flow's path if the module is outputting a current while in the test lab but the driver is still not recognizing the loop.

[Gearmiester]

CICCO~ OK so here are the electrical diagrams that I have tried to use to connect the Parker Driver Card.

The PDF shows the Parker connection diagram

Denison Pump elect 1  jpeg shows how I connnected everything according to the initial post here, where the driver card did not work as it does not recognize the 4-20mA loop.

Denison pump elect jpeg shows my last attempt to feed the 4-20mA through a repeater barrier made by Stahl. Interestingly the Parker driver card recognized the 4-20mA loop but it smoked the driver card.

So as of yet still no idea what is going on.

[Gearmiester]

sorry fro double post

Here is the diagram with the Dwyer ASG (Analog Signal Generator) connected.

this set up works!

Why I have no idea...