Frequency measurement using 1208LS

[vmrak]

I have the board set up for single ended. What I dont understand is when I apply a 4hz square wave to the inputs I get the correct result. When I turn off the applied signal I get the strange values shown below I was expecting to see zero.

 

 

[Fausto]

Hello @vmrak.

Thank you for the example.  Your device does not appear to have an issue if it is capturing expected data values with valid signal connections.  Without a signal connected to the input channels, the USB-1208LS is measuring surrounding environmental noise.  MCC devices were designed to work with low impedance signal sources.  MCC device inputs that are unconnected (open) are considered high impedance and will charge up to various stray voltages.  Notice that your detected amplitudes are in the microvolt range, so disregard those values.

Also, as you increase the signal frequency to the device, consider increasing the sample rate and number of samples per channel.

Regards,

Fausto

[Fausto]

Hello @vmrak.

Which version of Windows OS, LabVIEW, and InstaCal are you using?

Please share your vi example.

The behavior may be from the frequency vi.  

Add a display plot to your example. 

Regards,

Fausto

[vmrak]

windows 10, labview 2013, instacal 6.74.

Yeah Im thinking it has something to do with the freq.vi

freq test.vi

[vmrak]

And I did add the clear task that I forgot. I have tried this with reading just one channel and still get a reading when the input is grounded