Problems with usb 6009

[Redbull]

I just get a daq usb 6009 and i have several doubts.
First the green light near the usb connector is all time blinking, is this correct?.
I´m trying to adcquire a signal from a thermocouple by mean of a AD594 if i check the voltage with a voltimeter this value it´s ok. But when I connect the exit of the ad594 to the daq the value in the laptop is not stable, it has too much variations. I don´t know why.
I connect earth to pin 1 and ad594 to pin 2 (AI0), as Single Ended signal.

Thank you very much for your he

[jasonv]

The flashing LED probably simply indicates that data transfer is occurring over the USB bus. As for your unstable signal, I would recommend trying to make the same measurement while making the connection in differential mode to see if that makes any difference. To do this, connect your positive terminal to AI0+ (pin 2), and your negative terminal to AI0- (pin 3).

If you would still like to be able to use single ended mode (in order to be able to use all 8 AI channels at once, for example), then you could consult the following KB about field wiring and noise considerations and attempt to resolve the grounding issues that might be causing your signal to be floating:

http://zone.ni.com/devzone/conceptd.nsf/webmain/01F147E156A1BE15862568650057DF15?opendocument

[Redbull]

Thanks for your answer.

The led is blinking without any cable wiring in the analog inputs. When I connect the usb card to the laptop the led begins to blink and never stop.I´m not sure that the card is running ok.
When I measure the voltage readed by the card I´m measuring in the screws of the card.
For Example I measure with the voltimeter 0.500 mV and I´m seeing on the 0.430 mv and unstable.
That means that If there are some kind of noise it had to be produced by USB card. is it possible??.
And if it is possible how can i solve it?.

Thanks

[Redbull]

Hello Again
I,ve just probe to fix ai0 with gnd (with a short wire), and with the datalogger includes in the cd. I have got a 7mV variation.
In ai2 that is not fix to anything i,ve got a variation about 30mV. I think is too much. Could be the USB daq wrong???

Thanks

[Chris_B]

For the USB-6008 and 6009, the flashing LED indicates that the device is connected to the machine and has enumerated. It does not indicate that it is transferring data.

As a side note, the DAQPad-6015, DAQPad-6016 and the SCXI-1600 do have a yellow activity LED, which does flash when the device and host are communicating, as well as a ready LED (which is solid green unless the device is disconnected).

[Redbull]

Then the flashing led is ok or not?.
It has to be always flashing or it has to be always on.

Thanks

[Diego_M]

Hi Redbull,

I hope my reply may help you in order to work with your board.

Firstly, the flashing LED is normal to blink all time. That is indicated you that the communication with the PC is pefect.

Reference to how fluctuating the measure, it´s normal the measure fluctuates due to you fixed one wire and you have been measured a floating voltage. This board only admits differential and single ended mode.

If you want to read 0 volts through NI Datalogger, you probe to fix AI0+ with GND and AI0- with GND and choose "differential" under "input terminal configuration" field on your NI Datalogger.

Moreover, you can fix a wire to PIN 31(+5v) with PIN AI0+ and GND with PIN AI0- and choose "differential" on NI Datalogger and you´ll measure +5v. Other method to know if your board is working fine is to grab a battery and fix negative borne to AI0- and positive to AI0+ (differential mode).

I hope this helps you

Regards

Diego M.

[LBLguy]

The USB-6009 has an input resistance of 144 k and a voltage of 1.4 V at the bottom end of that 144 k. If the device supplying the input voltage is not capable of sinking current, then its output will be pulled up by the USB-6009. Try a resistor to ground or a gain = X1 op-amp buffer, to see if it helps.

[rborges]

I am using an USB 6009 to acquire data from a HPLC detector. The analog information enters through AI-0 and this is working fine. However, I use AI-1 for trigger the acquisition but it always read 1.4 V even in the absence of any connection. I have tried either using AI 1 and GND (pins 5&7) and AI 1+ with AI 1-. Both have the same voltage. I have connected also analogs with digital GND with the same, frustrating, results.

Could you please help me?

Thanks