PWM-520 low voltage problems

[Little_Dave]

Hi all.  I am having a problem with an FP-PWM-520 module and I'm hoping that someone can help.

I have a Fieldpoint system with two FP-PWM-520 modules in positions @7 and @8.  The two modules are powered by a dedicated 24V supply.  One module works properly but the second module does not output enough voltage to run our equipment (~4-6V per channel at 100% instead of ~24V).

I measured and got 23.96VDC across V and C.  I tried swapping the modules to see if it was a problem with the terminals but the problem moved with the module.

Is there a configuration setting that i missed or is the module toast?

Thanks,

Dave

[NIJanell]

Hello Dave,

If you feel that your module may not be working correctly, I would call an applications engineer at 866.ASK.MYNI.  This could require that the defective module be returned to NI.  I do have a few questions about your set-up though:

1.  When you say you swapped the modules, what exactly do you mean?  Is the power supply connected to the module at slot 7 when that module works correctly?  If you attach the power supply directly to the module in slot 8, do you still have this issue? 

It sounds like you may just need two devoted power supplies, one for each module. 

2.  Have you tried using one power supply per module?  Does one module still not output the correct voltage?

3.  Try setting up your system using only one module and one power supply.  Does the system work?  What if you switch the modules, but still only have one connected?

Good luck!

Janell R | Applications Engineer

[Little_Dave]

Hi Janell.  Thanks for the reply.  Here are the clarifications you are looking for.

1. The power supply is connected to the V and C terminals at postion @7 in the Fieldpoint train.  The V and C terminals at position @7 are then jumpered to the V and C terminals at position @8.  As originally connected, the two PWM modules share the same power supply.  This power supply is used exclusively for the two PWM modules.

When I say that I swapped modules it means that I took the two modules and switched their position in the train (ie: the module that was at position @7 was moved to position @8 and the reverse was done with the other module).  When I swapped the modules, the low voltage outputs followed the module that I suspect has a problem.

2. I did try isolating the supply to each module.  The result was that one module worked properly and the other still put out the low voltages.

3. I will try this in the morning.  Is it possible that the PWM modules are interfering with each other?

Thanks,

Dave

[NIJanell]

Hello Dave,

If the problem continues to follow the module, this definitely sounds like it may be an RMA.  Please go to www.ni.com/ask to create a service request and speak over the phone with an applications engineer.

Regards,

Janell R