USB 6008 - 50405 error (on connection of Siemens Micromaster frequency inverter drive)

[maltrap]

Hello Board

I have 2 USB 6008 daq cards connected to my experimental set-up. 

The one daq is used to measure various pressure (voltage) from differential pressure and temp sensors.

The 2nd daq is used to output various signals. Namely one to a Siemens Micromaster 440 drive, which then powers a star connected 3 Phase motor

The system "works" that is voltages are read, and voltages are outputted where necessary

HOWEVER, neally every time I turn the Siemens drive on (pushing the on button on the drive itself) my daq card connected to the sensors dies and a 50405 error appears. Sometimes plugging in and out the device resolves this issue

I have read many threads on this, however I feel that this problem is not  with connecting various USB devices. 

Is it possible that the 50405 error is like a protection due to bad grounding of the Siemens drive and motor ? ( All the devices are connected to the same metal frame and my concern is that an ubalnced load creates voltage in frame)

Or is the USB 50405 error only due to comms.

Thanks in advance

Mark

(attached is one of vi.s)

[Whit-E_Wall-E]

It does not seem like that error will occur due to bad grounding.  However I did find another forum post that may be relevant to your problem.  http://forums.ni.com/t5/Multifunction-DAQ/6009-USB-DAQmx-Read-Error-50405/m-p/1328551?requireLogin=F...

Another option would be to call a Device Reset in your program.  Example code for that can be found at https://decibel.ni.com/content/docs/DOC-9846.

Also are you seeing this error in MAX or when running your program?

What Operating System are you using?

[maltrap]

Hi M. Whitaker

I am using a windows 7 Toshiba laptop with 3usb ports. 

Yes the same error occurs in Max. I tried a device reset in MAX when this error occurred, it said that is was not possible.

The problem is rather inter. Sometimes I can run the Siemens drive no problem, other times it kills the DAQ at drive turn on

Is there a possibility that the drive draws too much current from the DAQ causing it to "shut down" the weird part is that it kills the DAQ that it is not connected too. (well most of the time, sometimes both). The Siemens has been commisioned to take a 0 - 5 volt analog control signal

Ill try the device reset code and see if it helps

Thanks

[johnsold]

Mark,

I suspect that the problem is due to ground currents.  USB devices connect to the computer ground and it seems that some devices are quite sensitive to spurious currents flowing on that cable.  I have never seen anything which suggests whether the problem is in the external device or in the hub circuit in the computer.

The ground connection in power systems is there primarily to protect the power network and secondarily to protect people and equipment from catastrophic damage. It was never designed for use as a measurement reference potential and generally does not work well for that purpose.

1. Is the reference in the Siemens drive connected to "ground"?  I have seen controllers with some really strange input connections.

2. If possible (and my guess is that it will not be possible), connect the grounds of each device to the "master" ground reference at exactly one point by exactly one conductor.  The USB-computer connection must be treated as one device because their grounds are connected through the USB cable.

3. Check the voltage difference between the ground of the circuit which powers the copmuter and measurement system and the ground of the circuit supplying the Siemens drive and motor.  Also check the voltage between your metal frame and the power circuit grounds.  If you can do so safely, make these checks with the motor and drive off and on.

4. If you have a suitable clamp ammeter, check the currents in any grounds you can reach, again with the notor on and off. The voltage and current checks should be done at DC, at the power line frequency, and in a frequency range which includes the switching frequency of the Siemens drive.

5. Is the laptop power supply grounded?  Is the computer ground connected to the power ground?

6. Are all the USB ports connected to the same hub or does the computer have multiple hubs?

Lynn

[maltrap]

Hi Lynn

With regards to the computer hub. As far as I know, all the USB devices are connected to 1 hub.( there are 3 USB ports, the 2 that are directly on top of eachother give the biggest issuer if used simultaneously)

I have also noticed that frequency of the error is almost not existent, when I power the Siemens drive through a potentiometer from a external supply 0 - V., but if I try use the 5v out on the daq, it dies and I get a 50405 error.

The laptop power supply is connected to ground. The laptop, and Siemens drive and the measurement devices (Johnson controls temperature, and pressure sensors ) are all connected to the same ground (earth)

I will do the tests that you suggested this week, and post the results.

Thanks for the help so far

Mark

[johnsold]

Mark,

How much current does the Siemens require on the 0-5 V input?  The USB-6008 analog outputs can source a maximum of 5 mA.  If the Siemens requires more than that, or, equivalently, has an input impedance less than 1000 ohms, the 6008 would not be able to drive it.

Lynn