My PCI 8431 2 is not reading data

[Jose_Perez]

Hello,

I'm using the PCI 8431 2 to connect a WattsOn power transducers via RS485, I used to get a reading, but now the WattsOn program stays at float as if it's waiting for a responce. That Watson program displays the number of samples for TX and RX, I've notice that when the rs485 is connected to the PCI 8431. I get TX readings, but very few RX readings.

I've used a RS485 to USB converter and I was able to get readings with the WattsOn program, so I know that the wattson transducer works well and the rs485 terminals are good. I would like to know why suddenly the PCI 8341 is having trouble reading the data from the transducer and if there is a way to fix this.

Thanks for your time,

Jose

[Matt.M]

Hello Jose,

First, have you changed any National Instruments drivers or software recently?

Second, I recommend you try a loopback test with your board.  Here is a Developer Zone tutorial on how to perform this test: How to Do a Serial Loopback Test.  You can use HyperTerminal, Putty, or any other communications console.

If the loopback test succeeds then your issue is probably not the PCI-8431.  If the loopback test fails, try the card in a different computer, if you can and do a loopback test there.  You can also try uninstalling and re-installing the drivers that came with your device.

If, after trying those steps, the cards still does not seem to be working you might need to do a RMA.  Here is a link with more details on the RMA process: Sending a National Instruments Board in for Repair or Calibration

Regards,

Matt M.

[Jose_Perez]

Hello,

I just ran the loopback test with the Hyper Terminal, Automation Explorer, and 485 Loopback Test 2 wire Auto_L 8.6.vi and I had responce from the PCI 8431.However, I'm still not getting any reading when using the WattsOn software.

Also, we ordered this computer with the PCI - 8431 already installed; therefore, we don't have a software for this card.

Thanks for the help so far,

Jose

[Matt.M]

The drivers for your PCI-8431/2 are located here: NI-Serial Drivers

You can try updating to the latest version of the drivers and see if that fixes your issue.

EDIT: 3.8 is the latest version.

Regards,

Matt M.

[Jose_Perez]

I just updated the NI-Serial Driver and I'm still not getting RX readings. I've also checked the RS485 wires and they are sending data.

I'm also using the serial quick reference guide for the RS485 connection (http://www.shrum.net/files/serial_quickref.pdf). In our case, we have 3 wire RS485 (one GND, +, and, -). I've tried different combinations, but I still get the same result. What might be a good way to figure out the problem here?

Thanks for all the help so far,

Jose

[Dan_N]

Hi Jose,

When you say you've tried different combinations, do you mean that you have attempted to wire different combinations of the Rx+ and Tx+ wires to the + input of the Transducer? To operate over RS-485 in half-duplex (2-wire) mode, you need to wire the Rx+ and Tx+ wires to the + input, and the Rx- and Tx- wires to the - input. Also, double check that you've got the correct baud rate on both ends, and are using the proper termination resistors on each side (should be 120 ohms).

Best,

Dan Nelson

Applications Engineer

[Jose_Perez]

Dan,

I verifed the Resistor and that the Rx+ and Tx+ wires are in the + input, and the Rx- and Tx- wires to the - input. Still I'm not getting any reading. I can't think of anything else to do...

Jose

[Matt.M]

Jose,

It appears that the PCI card is working properly.  You might want to contact the Watts-On people and see if it is a compatibility issue with their software and our hardware.  You can try to communicate with the device manually through a console or Measurement & Automation Explorer.

If you navigate to the Start Menu --> All Programs --> National Instruments --> Measurement & Automation Explorer.  Then expand My System --> Devices and Interfaces --> Serial & Parallel, right click on your device and open the VISA test panel. Set the serial settings correctly according to what your transducer expects then go to the Input/Output option at the top and write the *IDN?\n command to your device.  You will be able to see any data it returns in the "Return Data" window.  If the device is responding correctly it should identify itself when issued that command.

Regards,

Matt M.

[Jose_Perez]

Matt,

I tried the Measurement & Automation Explorer INPUT/OUTPUT and write *IDN?\n. The result was"Write Operation (*IDN?\n) No Error". Is this to test the card, because I tried something like this before and got similar results? I know that the card is working good though.  

Thanks,

Jose

[Matt.M]

This is to test the connection to your transducer.  You should have the cable connecting your card and the transducer, then issue that command.  In the result it should show the transducer identifying itself.  Saying something like Watts-On Transducer version no. something.  If it doesn't then the transducer isn't responding.

Matt