Trigger start when a external device turns on

[kammer@pi-berlin.com]

Hello,

I measure with the USB 6255 some analog voltage signals which are export as an excel sheet via labview (first picture). I use the AI 0...71 and AO GND of the USB 6255 for the voltage signals (you can see at the second picture).

To start the measurement, I set a trigger in Labview via DAQ Assistant. The trigger is on APFI 0 of the USB 6255 and is set on 5 V. 

I can start the Labview programm the USB wait for a signal over 5 V for the APFI 0. But when I turn on other device which is connected to the same 3-way current distributor as the USB 6255 is , the trigger get a signal and the measurement start, without any signal which a want to measure. 

Can someone help me there?

Thanks in advance!

[GerdW · Accepted solution]

Hi kammer,

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kammer@pi-berlin.com wrote:

I use the AI 0...71 and AO GND of the USB 6255 for the voltage signals (you can see at the second picture).

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I recommend to use the AI GND instead of the AO GND…

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kammer@pi-berlin.com wrote:

To start the measurement, I set a trigger in Labview via DAQ Assistant.

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I recommend not to use the DAQAssistent, but plain DAQmx functions…

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kammer@pi-berlin.com wrote:

But when I turn on other device which is connected to the same 3-way current distributor as the USB 6255 is , the trigger get a signal and the measurement start, without any signal which a want to measure. 

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I recommend to switch on "that other device" before you start your measurement VI.

I recommend to power "that other device" from a different power supply.

I recommend to hook up a scope to analyze what's happening on your APFI pin when you switch on "that other device"…

[kammer@pi-berlin.com]

Thanks for the help!

Best regards

Kammer